Analytical Experiments

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Laboratory Experiments in Analytical Chemistry

CHEM 3332

Analytical Chemistry Division

Department of Chemistry

University of Connecticut

Storrs, CT 06269 - 3060

Contributing Authors:

James Stuart, Jane Knox, Pedro Cid-Aguero and Abhay Vaze


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Table of Contents

Syllabus for the Laboratory Part of CHEM 3332

Introduction

Safety

Attendance

Notebook

Reports & Paper

Grades

Materials

Assignments

Before you start

Policies & Procedures

Experiment Schedule

Academic Honesty

The Laboratory Notebook

1. Using Laboratory Notebook

a. Safekeeping

b. Organization and Readability of the Lab Notebook

c. Quality of the Record Keeping

d. Guidelines for Keeping the Notebook

2. Contents of the Notebook

a. Table of Contents

b. Dates

c. Title of Experiment

d. Experimental

e. Data

f. Data Tables

Example of a Table

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g. Notes

h. Calculations

i. Results

3. Grading of the Laboratory Notebook

a. Physical Aspects

b. Format

c. Neatness

d. Organization

e. Completeness

f. Appropriate Record of Data

4. How the Lab Notebook will be graded?

Warning about Academic Misconduct!

PreLab Report

Post Lab Report

Laboratory Paper

Warning about Academic Misconduct

Writing the Paper

Submitting Reports and Lab Paper

Lateness Policy and Lab Preparedness

a. Prelab Report

b. Post lab Report

c. Lab Paper

Using Analytical Balances

General Rules

GA1 Analytical Techniques and Measurements

Use of the Analytical Balances

a. Precision of Various Balances

b. Use of the Digital Balance

c. Sources of Determinate Weighing Errors

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Calibration of Volumetric Glassware

a. Buoyancy Corrections

b. Direct Calibration of 25 mL Pipet

c. Direct Calibration of a Digital Pipet

Determination of the Density of Antifreeze

Questions/Topics for the Quiz

Calculations &/or Questions for Post lab Report

Datasheets

GA2 Acid Base Titration

Solutions and Chemicals

Standardization of ~ 0.1M NaOH against the Primary Standard KHP

Determination of Percent KHP in an Unknown Mixture

Calculations for Prelab Report


GA4 Analysis of Calcium by EDTA


Preparation and Standardization of a 0.03M EDTA Solution

Preparing Calcium Standard

Determination of the Indicator Blank

Standardization of ~ 0.03M EDTA

Determination of the Calcium in an Unknown Calcium Sample

Water Sample



GA5 Iodometric Titration of Ascorbic Acid in Vitamin C Tablets


Glassware

Preparation of the Thiosulfate Solution

Preparation of the Potassium Iodate Solution

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Standardization of the Thiosulfate Solutions

Equations

Analysis of ascorbic acid in the Vitamin C Tablets



GA7 Potentiometric Titration


Equipment

Determination of the Equivalence Point

Standardization of the pH Meter with Two Standard Buffers

Standardization of HCl by Potentiometric Titration

Potentiometric Titration of Potassium Acid Phthalate (KHP)

Potentiometric Titration of a Diprotic Acid


Calculations &/or Questions for Pre Lab Report


GA8 Ion Selective Electrode: Measurement of Fluoride Ion Activity in Mouthwash,

Toothpaste & Drinking Water


Equipments

Glassware

Preparation of Standard Solutions

Adjusting the Zero of the Millivoltmeter

Cautions Concerning Use of Electrodes and Meters

Determination of Potentials for the Calibration Curve

Determination of Fluoride in Toothpaste (optional)

Determination of Fluoride in the Mouthwash

Determination of Fluoride in Water Samples

Determination of Fluoride in Unknown

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GA16 A Study of Atomic Absorption

Solutions and Chemicals Required

Equipment

Instrument Warmup

Preparation of Solutions

a. Calcium Solutions

b. Unknown Solutions

Cleaning Up



GA20 High Speed Liquid Chromatographic Separation of Various Compounds Found in

Coffee, Tea and Soft drinks

Instrumentation

Equipment

Solution and Chemicals

Glassware

Getting Started

a. Adjustment of Solvent Flow

b. Filling the Sample Loop

c. Injection of the sample

d. Introduction of Sample into the Column, and Recording of the Peak

e. Identification of Components in Mixtures

f. Theoretical Plates & Peak Symmetry

g. The Soft Drink or Coffee and/or tea sample

Instrument Shutdown

Recording All Experimental Conditions

Calculations and Questions for the Lab Paper

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GA21 Spectrophotometric Determination of Iron


Preparation of Standard Solutions

Preparation of Unknown Solution

Spectrophotometer measurements

Topics for the Quiz


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Syllabus for the Laboratory Part of CHEM 3332

Department of Chemistry, University of Connecticut

Quantitative Analytical Laboratory

Chemistry 3332

Instructor: Dr Abhay Vaze

Email: abhay.vaze@ uconn.edu

Office hours (T414): Wednesday & Thursday 9 AM 5 PM, by appointment

Introduction

C h e mi s tr y 3 3 32 i n tr o du c e s a n u mb e r o f e x pe r im e nt s o r ie n te d t o wa r d d e v el o pi n g e x pe r ie n c e i n

performing accurate and precise chemical measurements by both, classical and instrumental

t e ch n iq u e s. T h e se e x p er i me n ts w i ll g i ve y o u s k il l s i n s o lu t io n s p r ep a ra t io n , u n d er s ta n d in g o f

instrumentation, data interpretation, results evaluation and preparation of scientific reports.

Safety

I n m an y o f t he e xp er im en ts , y ou w il l b e h an dl in g t ox ic o r d an ge ro us c he mi ca ls . S pe ci al

precautions will be needed, so follow the instructions carefully. Safety Goggles must be worn at

a ll t im es i n t he l ab . Y ou m us t w ea r S ol id S ho e s ( no s an da ls o r o p en t oe s ho e s) . F a il ur e t o d o s o

will re sult in your dismissa l fro m the lab pe riod without make up op tions. It is your

r e sp o n si b il i ty t o c l ea n y o ur g l as s wa r e. F o r m o re i n fo r ma t io n , p l ea s e s e e: P a g e 3 0 , Q u a nt i ta t iv e

Chemical Analysis, edition 8th by Daniel Harris, W. H. Freeman and Company NY.

Attendance

A t te n d an c e i s M a nd a to r y a n d a l l s t ud e n ts s h ou l d b e o n t i me . O n l y w e l l d o c u me n te d a b s e n ce s t o

the laboratory will be considered, and makeups will depend on availability of instructors.

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Notebook

A b o un d n o te b o ok , w i th n u mb e re d p a g es a n d c a p a bl e o f p r od u c in g c a rb o n c o p i es , i s r e qu i re d b y

t he f ir st l ab p er io d i n w hi ch e xp er im en ts a re p er fo rm ed . A ll d at a a nd o bs er va ti on s m us t b e

d ir ec tl y r ec or de d i n y o ur n ot eb o ok ( ex c ep t f or G A1 e x pe ri me nt , s ee e x pe ri me nt h a nd ou t f or

d e ta i ls ). A l l e n tr i es m u st b e m a de i n i n k. R e f e r t o " T h e L a b o r a t o r y N o t e b o o k " s e c t i o n f o r f o r m a t

a n d e di to ri al s ty le . T he n ot eb oo k m us t n o t b e r em ov ed f ro m t he l ab o ra to ry u n ti l t he e nd o f t he

semester.

Reports & Paper

P r e- L ab r e po r t: T o a s su r e a d v an c e p r ep a ra t io n , y o u w i ll b e r e qu i re d t o p r ep a re a p r e- l ab o ra t or y

r ep or t. P re -l ab r ep or t n ee d s t o b e s ub mi tt ed e le ct ro n ic a ll y (PDF) t o t he l ab i ns tr uc to r a t l ea st

TWO daysprior to the scheduled experiment. See section on Pre-lab Report for details .

P os t L ab r ep or t: i s r eq ui re d f or e ac h e xp er im en t. S ee s ec ti on o n Ex pe ri me nt R ep or t f or

d e ta i ls . E a ch s t ud e nt w i ll s u bm i t h i s/ h er o w n i n de p en d e nt r e po r t. N o p l a gi a ri s m w i ll b e t o le r at e d.

After completion of the experiment, lab report is due in the following week.

Electronic copy (PDF document) of the Experiment Report is due on:

F o r M o nd a y /W e dn e sd a y S e c ti o n, r e po r t i s d u e o n W e dn e sd a y b y 1 0 a m .

F o r T u e sd a y /T h u rs d ay S e ct i on , r e po r t i s d u e o n T h ur s da y b y 1 0 a m .

I f t he E xp e ri me n t R e p or t i s l at e, t he re w il l b e a c um ul at iv e 1 0 p o in ts d e du ct io n p e r d a y t he l ab

report is overdue.

L a te r e po r ts d u e t o a v a li d a n d w e ll - do c u me n te d e m er g en c y w i ll b e c o n s id e re d o n a n i n d i v id u a l

case basis.

L ab o ra to ry P ap e r: A f ul l p a pe r w il l b e r eq u ir ed f or o n e a ss ig ne d e xp e ri me n t. S ee s ec ti on o n

La b or at or y P a pe r f or d e ta il s. E ac h s tu de nt w il l s ub mi t h is /h e r o wn i nd ep en d en tl y w ri tt en

paper. S ee Ex pe ri me nt S ch ed ul e t o k no w t he e xp er im en t a ss ig ne d f or th e l ab p ap er .

Laboratory Paper is due on Laboratory Paper is due on Thursday, April 28 2016, at 10.00 am.

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Grades

CHEM 3332 Course Grade: Course grade will be based:

52%on examinations (4 examinations, each will constitute 13% of the course grade)

35%on the Laboratory

Pre-Lab Report 5%

Post Lab Report GA1, 2, 7 15%

Post Lab Report GA4, 5, 8, 16, 21 60%

Lab Paper GA20 15%

Lab Notebook 5%

Laboratory notebook will be assessed and graded, without priors notice, several times

during the semester.

13%on Quiz (8 quizzes in a semester).

Quizzes will be based on Laboratory (see Experiment handouts for topics/questions) and Class

Material.

Materials

All laboratory material is available on HuskyCT.

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Assignments

B ef or e b eg in n in g a ny e x pe ri me n t, y o u must h a v e r e ad t h e a s s i gn e d b a c kg r ou n d m a te r ia l f r om

l ab m an ua l, a s w el l a s f ro m t he i nd ic at ed c ha pt er s i n t he c ou rs e t ex tb oo k ( Ha rr is : 7th o r 8th

Edition)

1. G A 1 A nal yti cal T echni ques and M eas ur ement s ( C hapt er s 1 4)

2. G A 2 A cid- B ase T i t rat i on 1 (C hapt ers 7 - 11)

3. G A 7 A ci d-B as e P ot ent i omet r i c T it r at ion ( C hapter s 7 - 11)

4. G A 4 A nalys i s of C al cium B y E D TA t i tr at i on ( E d 7th: 12 & Ed 8th: 11)

5 . G A5 I od o me tr ic T it ra ti on o f A sc o rb ic A ci d i n V it am in C T a bl et s ( E d 7th: 1 5 & E d 8th:

16)

6 . G A 8 I o n S e le c t iv e E l ec t ro d e : T h e M e as u re m e nt o f F l uo r id e I o n A c t i vi t y i n M o ut h wa s h,

Toothpaste, Drinking Water (Ed 7th: 14, 15 & Ed 8th: 13, 14)

7. G A 16 A S t udy of C a by A t om i c A bs or pt i on S pect ros copy (E d 7th: 21 & Ed 8th: 20)

8 . G A 20 H i gh S p e ed L i qu i d C h r o ma t og r ap h ic S e pa r at i on o f V a r i ou s C o m p o un d s f o u n d i n

soda, Coffee or Tea (Ed 7th: 23, 25 & Ed 8th: 22, 24)

9. G A 21 S pectr ophotom et ri c D et erm i nati on of I ron ( E d 7th: 18-20 & Ed 8th: 17, 18)

Before you start

Please see following sections of the lab manual:

Pre-Lab Report


Safety

Attendance

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Policies & Procedures

http://policy.uconn.edu/

Policy against Discrimination, Harassment and Inappropriate Romantic Relationships

http://policy.uconn.edu/?p=2884

Students with disabilities

Please contact me during office hours to discuss academic accommodations that may be needed

during the semester due to a documented disability. The Center for Students with Disabilities

(CSD) engages in an interactive process with each student and reviews requests for

accommodations on an individualized, case-by-case basis. Depending on the nature and

functional limitations of a students documented disability, he/she may be eligible for academic

accommodations. CSD collaborates with students and their faculty to coordinate approved

accommodations and services for qualified students with disabilities. If you have a documented

disability for which you wish to request academic accommodations and have not contacted the

CSD, please do so as soon as possible. The CSD is located in Wilbur Cross, Room 204 and can

be reached at (860) 486-2020 or at [email protected]. Detailed information regarding the process

to request accommodations is available on the CSD website at www.csd.uconn.edu.

http://www.csd.uconn.edu/

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Experiment Schedule

Date Section T1 T2 T3 T4 T5 T6 T7 T8

19-Jan Tu/Th Meeting20-Jan M/W Meeting

25-Jan M/W GA1 GA1 GA1 GA1 GA1 GA1 GA1 GA1

26-Jan Tu/Th GA1 GA1 GA1 GA1 GA1 GA1 GA1 GA1

27-Jan M/W GA1 GA1 GA1 GA1 GA1 GA1 GA1 GA1

28-Jan Tu/Th GA1 GA1 GA1 GA1 GA1 GA1 GA1 GA1

1-Feb M/W GA2 GA2 GA2 GA2 GA2 GA2 GA2 GA2

2-Feb Tu/Th GA2 GA2 GA2 GA2 GA2 GA2 GA2 GA2



Related Chapters Ch. 2, 3 & Ch. 4


8-Feb M/W GA20

9-Feb Tu/Th GA20

10-Feb M/W GA20

11-Feb Tu/Th GA20

15-Feb M?W GA20

16-Feb Tu/Th GA20

17-Feb M/W GA2018-Feb Tu/Th GA20

Related Chapters Ch. 22 & Ch. 24

Laboratory Paper is due on Thursday, April 28 2016, at 10.00 am.






29-Feb M/W GA4 GA4 GA4 GA4

1-Mar Tu/Th GA4 GA4 GA4 GA4

2-Mar M/W GA4 GA4 GA4 GA4

3-Mart Tu/Th GA4 GA4 GA4 GA4

Related Chapters Ch. 8 11

Continued on the next page

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7-Mar M/W GA4 GA4 GA20

8-Mart Tu/Th GA4 GA4 GA20


10-Mar Tu/Th GA4 GA4 GA20





Related Chapters Ch. 11 Ch. 22 & Ch. 24



28-Mar M/W GA5 GA5 GA8 GA829-Mar Tu/Th GA5 GA5 GA8 GA8

30-Mar M/W GA5 GA5 GA8 GA8

31-Mar Tu/Th GA5 GA5 GA8 GA8

4-Apr M/W GA8 GA8 GA5 GA5

5-Apr Tu/Th GA8 GA8 GA5 GA5



Related Chapters Ch. 13 15










25-Apr M/W26-Apr Tu/Th

27-Apr M/W Checkout

28-Apr Tu/Th Checkout

Related Chapters Ch. 17, 19, 20


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Academic Honesty

S t at e me n t o n A c a de m ic H o n es t y ( P a r ts c o pi e d f ro m P a g e 1 5 - 1 6 o f t h e U n i v e rs i ty o f C o nn e c ti c ut

pamphlet entitled: Student Conduct Code revised May 10, 1996 & available from the Vice

President for Student Affairs, 352 Mansfield Road, U-121)

A ll s t ud e n ts h a v e t h e r i gh t t o p u rs u e t h ei r a c ad e m ic c a re e rs i n a n a t mo s ph e re b a s e d o n h o n es t y

a n d t ru st . A ct s o f a c ad em ic m is co nd u ct d e st ro y t ha t a tm os ph er e, v io la te t ha t t ru st , a n d a re

t h er e fo r e s u bj e ct t o p e n al t y. . . A f u nd a me n ta l c o nc e p t o f a l l e d uc a ti o na l i n st i tu t io n s i s a c a de m ic

h o ne st y. .. M is re pr es en ta ti on o f s om eo ne e ls e s w or k a s o ne s o wn i s a m os t s er io us o ff en se i n

any academ ic s et t ing. . . No academ ic m i s conduct , i ncl udi ng any f or m s of cheat i ng and pl agi ar i sm ,

c a n b e c on d on ed . A ca d em ic m is co n du ct i nc lu d es b ut i s n o t l im it ed t o p ro vi di ng o r r ec ei vi ng

a s si s ta n ce in any manner n ot a uth ori ze d b y th e i nst ru cto r i n t he c re ati on o f w or k t o b e

s u bm i tt e d f o r a c a de m ic e v al u at i on i n cl u di n g p a p er s , p r oj e ct s , e x a mi n at i on s , e t c. , p r es e nt i ng a s

ones own the ideas or words of another for academic evaluation without proper

a c kn ow le dg me n t, d o in g u n au th or iz e d a ca d em ic w or k f or w hi ch a n ot he r p er so n w il l r ec e iv e

c re di t o r b e e va lu a te d a n d p re se nt in g t he s am e o r s ub st an ti al ly t he s am e p a pe rs o r p ro je c ts i n

t w o o r m o re c o ur s es w i th o u t t h e e x pl i ci t p e rm i ss i on o f t h e i n st r uc t or s i n v o lv e d .. . . A l s o , o n e i s

n o t a ll ow ed t o c o op er at e o r b e a n a cc e ss or y t o a no th er s a c ad e mi c m is co nd u ct . T hu s a s tu d en t

w ho w ri te s a p ap er o r d oe s a n a ss ig n me n t f or a n ot he r s t u de nt i s a n a cc o mp li ce a n d m u st b e h el d

a c c ou n ta b le j u st a s s e ve r el y a s t h e o t h e r. I t i s p e rh a p s l e s s o b v i ou s , b u t i t i s e q u a l ly l o gi c al , t h at a

s tu d en t w ho k n ow in g ly p e rm it s a no th e r t o c o py f ro m h is o r h er o wn p ap er , e x am in a ti on , o r

project should be held as accountable as the student who submits the copied material.

P ar t o f t he F ac ul ty s r es po ns ib il it y a nd u su al p en al ty ( re fe r t o t he f ul l t ex t f ou nd i n t he

Student Conduct Code)

.. .W he n a n i ns tr uc to r b el ie ve s t he re i s s uf fi ci en t e vi de nc e t o d em on st ra te a c le ar c as e o f

a ca de mi c m is co nd uc t, t he i ns tr uc to r s ha ll n ot if y t he s tu de nt i n w ri ti ng , a nd a ls o o ra ll y i f

possible, that unless the student requests a hearing to contest the instructors belief, the instructor

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shall impose the appropriate academic consequences warranted by the circumstances..... In

reference to the imposed consequences, the instructors of this course may consider the following

opinions of (1) awarding a Failure on the actual academic work in which the academic

misconduct was found (2) awarding an immediate Failure for the entire course, which might

include the recommendation to the Dean of Students for the immediate dismissal of the student

from the University, if the circumstances dictate.

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The Laboratory Notebook

T he p ur po se o f t he l ab o ra to ry n o te b oo k i s t o k e ep a p e rm an e nt r ec or d o f y ou r l ab or at or y w or k,

which can b e rea d an d und ersto od at a future time by b oth you and oth er scientists.

E xp eri me nt al w ork sh ou ld b e a bl e t o b e r ep ro du ce d b y so me on e e lse d ire ctl y fr om t he

description that you provide in your laboratory notebook.

1. Using Laboratory Notebook

T h e re a r e t h r e e m a jo r c o nc e rn s a b ou t t h e n o t e b oo k : ( a ) t h e s a fe k e ep i ng o f t h e l a b n o te b o ok , ( b )

the organization and readability of the lab notebook, and (c) the quality of the record keeping.

a. Safekeeping

I n l ab o ra to ry j ob s, t he l ab or at or y n o te b oo k b el on gs t o t he o rg an iz at io n f or w h om t he w or k i s

being done. There will be very specific guidelines about exactly how and where the notebook

m us t b e k ep t, ( in a ny c as e i t s t ay s a t t he w or k s i te !) G en er al ly , i f y ou a re d o in g r e s ea rc h a l l d a y ,

y o u w il l n ot h a ve t im e o r t he i nc li na ti on t o w or k o n y ou r l ab n o te b oo k o u ts id e o f t he l ab t o m ak e

i t l oo k n ic e. Y ou n e ed t o g et t he i mp or ta n t o b s er va ti on s i nt o t he l ab n ot eb o ok a s y ou a re d oi ng

t h e w o rk. T o h el p y o u g et i nt o th is h a bit , w e r e q ui r e y o u t o l ea v e y o u r l a b n ot e bo ok i n t he

laboratory . Y ou w il l b e m ak in g a c ar bo n c op y o f e ve ry th in g t ha t g oe s i nt o t he b oo k, a nd t ha t

copy may be taken with you as you leave the lab.

b. Organization and Readability of the Lab Notebook

T he m ai n c on c er n i s t he p er ma ne n t n a t ur e o f t he r ec o rd o f y o ur l ab o ra to ry a c ti vi ty . A b o u nd

n o te b oo k ( as o pp os ed t o s pi ra l) m in im iz e s t he c ha n ce o f l os in g p ag e s. G oo d q ua li ty , b la c k i nk

m in im iz es t he c ha n ce f or e ra su re s, o bs cu ri ng o f w ri tt en m at er ia l a n d p ro v id e s f or a c le a re r

photocopy in the event that it is necessary.

c. Quality of the Record Keeping

T he i mp or ta nc e o f b ei ng a bl e t o f in d y ou r p as t e xp er im en ta l w or k i n o ne p la ce c an no t b e

o ve re mp ha si ze d. N o o ne l ik es t o re do , o r re th in k p ast w or k th at h ad b ee n su cc ess fu ll y

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c o mp l et e d! W i th o ut c o mp l et e i n fo r ma t io n , w o rk c a nn o t b e r e pr o du c e d a n d v e ri f ie d . W i th o ut

well-organized information, the significance of experimental results might not be realized.

d. Guidelines for Keeping the Notebook

W it h t he a b ov e p oi nt s i n m in d , t he f ol lo wi ng g ui de li ne s f or k ee p in g l ab o ra to ry n o te b oo k h a ve

been developed.

1 . T h e n o t eb oo k m us t c on ta in b ou n d, n um be re d p ag e s. A c ar bo n c o py o f t h e p r im ar y p a ge

should be made onto the duplicately numbered page.

2 . E n tr ie s m us t b e m ad e i n t he n o te b oo k w it h g oo d q u al it y b al lp o in t p en , p re fe ra bl y b la ck .

A v o id w r it i ng o v er d a ta . I f a n e n tr y i s m a de i n e r r o r, c r os s o u t t h at e r ro r w i t h a s i ng l e l i n e

and add a simple legible explanation (for example, scale misread, etc.)

3. A l l ent ri es m ust be m ade i n dupl i cate us i ng t he car bon paper .

4. T he L ab Not ebook m us t be kept i n t he l ab at al l ti m es .

5. A ll d at a t ak en i n t he l ab or at or y m us t b e d ir ec tl y wr it te n i nt o t he l ab or at or y

notebook.

6. N o scr aps of paper w i l l be t ol erat ed!

7. A t t he e nd o f e ac h l ab p er io d o r a ny t im e t he re af te r, t he c ar bo n- co py p ag es o f

material may be taken home.

8 . A ft er s ub mi tt in g e xp er im en t r ep or t ( or l ab p ap er ) e le ct ro ni ca ll y, p le as e s to p b y t he

laboratory during laboratory hours to submit stapled carbon copy pages.

9 . T h e L ab N ot eb oo k s ho ul d b e l ef t o n t he d e si gn at ed s he lf a s y ou l ea ve t he L ab or at or y. I ts

presence will be checked after each laboratory period. Notebook is evaluated at least

t wi ce a s em es te r ( se e t he p ar t o n g ra di ng o f t he l ab or at or y n ot eb oo k a t t he e nd o f t hi s

section).

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2. Contents of the Notebook

a. Table of Contents

T hi s i s t he o n ly p ar t o f t he n o te b oo k, w hi ch d oe s n o t h a v e t o b e d up li ca te d. L ea v e t wo o r m o re

pages at the beginning of the book and be sure to keep this table up to date. You may use short

title (e.g., GA1) in the TOC, also include date and page #.

b. Dates

A lw ay s d a te t he w o rk i n a p ro mi ne n t p o si ti on w he re i t c a n e a si ly b e s ee n s o i t i s c l e ar w he re a

new day's work begins.

c. Title of Experiment

T he t it le i de n ti fi es t he e xp e ri me nt i n a f ew w or ds . I t s ho u ld p re c ed e a ny th in g r el at ed t o t ha t

e x pe ri me nt t ha t g oe s i nt o t he b o ok . O ne s ho u ld n e ve r o p en t he b oo k a n d f in d a b un ch o f d a t a o r

experimental description without a title.

d. Experimental

A ny c ha ng es t o t he p ro ce du re g iv en i n t he m an ua l, r aw d at a s uc h a s a mo un ts w ei gh ed o ut ,

solution volumes measured, unknown #, Purity factors of primary standards, etc.

e. Data

T he d a ta s ho ul d b e e nt er ed i nt o a t ab le d ir ec tl y a s i t i s t ak e n! N ot hi ng s ho ul d g o o nt o s cr ap s o f

paper!

f. Data Tables

T ab le s s ho ul d b e c on st ru ct ed w it h a s tr ai gh t e d ge , s ho u ld h a ve a t it le , a nd s ho ul d h a ve c le ar ly

l ab el ed c ol um ns a n d r ow s. N ot e t ha t d a ta i s r ea d d ir ec tl y f ro m t he m ea su ri ng d e vi ce . N um be rsc a lc u la te d f ro m a m ea su re me n t i s a r es ul t, b u t a s n o te d b e lo w m ay b e s ub se q ue nt ly a d de d t o a

table.

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Referring to the following table as an example, a table may contain both raw data (weights

obtained from a balance) as well as calculated results (calculated weights of sample obtained by

differences and by % sulfate calculated using an equation).

Example of a Table

Sample 1 Sample 2 Sample 3

g (Vial + Sample)

g (Vial - Sample)

g (Sample)

Avg. g (Crucible + Precipitate)

Avg. g (Empty Crucible)

g (Precipitate)

% Sulfate in sample

g. Notes

Any notes necessary to clarify, emphasize or interpret the data should be entered in the

Laboratory Notebook as the experiment progresses. Be especially careful to document any

change from the described procedure.

h. Calculations

If you do calculations during the lab, do them in the Lab Notebook.

i. Results

If you have the calculations in your Lab Notebook, the results should follow the calculations.

3. Grading of the Laboratory Notebook

The Lab Notebook grade is separate from the lab report and lab project grades and is an

evaluation of your record keeping. Each time a lab report is graded, an evaluation will also be

made of the material on the carbon copies of the lab book. In addition, the lab notebooks

themselves will be collected and evaluated as a whole at least twice a semester this collection

will not necessarily be announced! This grade is based on the following criteria:

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a. Physical Aspects

Is the notebook bound with numbered duplicate pages? Is the writing recorded in permanent

ink? Is there any unexplained crossing out of data?

b. Format

Are all the required sections included such as table of contents, dates, title, any changes to

experimental procedure from the lab manual, etc?

c. Neatness

Does the book have a neat appearance? Is there a lot of writing or crossing out of data,

scribbling, etc.? This is a working notebook so you are writing as you are doing therefore, we

do not expect it to be flawless, but neither should it be a total mess!

d. Organization

Is the material well organized? Can we find what we are looking for easily?

e. Completeness

Is all the information there, which is necessary for one to evaluate the quality of your work?

f. Appropriate Record of Data

Are the tables clear and well designed? Do the numbers include units?

4. How the Lab Notebook will be graded?

Grade Quality

10 Just about perfect hard to find much wrong

9 Very good book with a few minor problems

8 Good book but has definite areas that need improvement

7 OK but many things need to be straightened out

6 Mediocre can find most information but with a lot of work

5 Poor just about acceptable4 Unacceptable

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Warning about Academic Misconduct!

Please pay particular attention to the fact that all laboratory reports and laboratory paper that you

submit to be graded fall under the general category of student's original work. Any a case

that it is observed that there has been deliberate copying from another students report and both

reports are handed, both will be considered as act of plagiarism which would be dealt under the

rule of Academic Misconduct as specified in the Student Handbook.

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Pre-Lab Report

R ea d t h e e xp e ri me n t c a r ef u ll y b e fo r e c o m in g t o t h e l a b . T h e e x p er i me n ta l p r oc e du r e i s i n

r e as o na b ly e x pl i ci t d e ta i l. W h en y o u r e ad t h is p a rt b e fo r eh a n d, t r y t o i m a g in e w h a t i t i s y o u w i ll

be doing. Also, attempt to figure out the whys of the experimental setup and procedure.

1. The pre-lab report refers to following aspects (expected length 1 1.5 pages).

Objective(s) (few sentences)

Indicate key equations.

E x p er i me n ta l r e qu i re m e nt s : I n di c at e t h e i n st r um e n ta t io n a n d /o r s p ec i al a p p ar a tu s

needed for the experiment.

I n cl u de a g e ne r al o u tl i ne o f t h e e x pe r im e nt a l p r o c e du r e, b y i n di c at i ng t h e m a i n s t e ps

to follow. No need to give details as they are already in the lab manual.

P re -c a lc ul at io ns : I f s ol ut io n p re pa ra ti on s a re n e ed e d, m ak e s ur e y o u h a ve a ll t he

calculations done (or figured out) to insure an efficient procedure.

I de nt if y c ri ti ca l s te ps i n t he e x pe ri me nt p ro ce d ur e t ha t c a n b e d et er mi na nt i n i ts

successful results.

Safety: List the hazards and the personal protective equipment needed to avoid them.

T he re s ho ul d b e o ne , s in gl e d oc u me nt f or t he p re -l ab r ep or t. T h is m ea ns t ha t e q u at io ns a nd

pre-calculations need to be typed in using equation editor. Document Margins ( L ef t 1 , R i gh t

2.5, Top and Bottom 1). Line Spacing 1.5.

P r e- l ab r e po r t n e e ds t o b e s u bm i tt e d e l ec t ro n ic a ll y (PDF d o c u me n t) t o t h e l a b i n st r uc t or a t l e as t

TWO days prior to the scheduled experiment.

Please Note

Pre-lab Report will not be graded if written in essay format.

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Post Lab Report

P os t l ab R ep or t MUST b e s u bm i tt e d electronically v i a e m a i las a PDF. T h e r e s h o u l d b e o n e ,

s i n gl e d o c um e nt c on ta in in g a ns we rs , t ab u la te d d at a, p lo ts , s am pl e c a lc u la ti on s, etc. No

h a n d- w ri t te n a s si g nm e nt s w i l l b e a c ce p te d . S a mp l e c a l c u la t io n s a r e m u st a n d n e e d t o b e t y pe d i n

M ic ro so ft W or d e qu at io n e di to r ( or f or mu la e di to r i n O pe no ff ic e w or d p ro ce ss or o r

e qu at io n e di to r i n G oo gl e D oc s ). P lo ts f ro m s pr ea ds he et s of tw ar e ( Ex ce l o r G oo gl e

S h e et s ) s h ou l d b e p a st e d i n t o t h e w o r d p r oc e ss o r d o c u m en t ( W or d o r G o og l e D o c s , etc)

before creating a single PDF d o cu me nt f or s ub mi ss io n. Document Margins ( L ef t 1 , R ig h t

2.5, Top and Bottom 1). Line Spacing 1.5.

N o f or ma l l ab r ep or t: J us t a ns we r q ue st io ns f ro m t he e xp er im en t h an do ut a nd s ho w

calculations.

Please Note

Post Lab Report will not be graded if written in essay format.

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Laboratory Paper

Warning about Academic Misconduct

P le as e p a y p ar ti cu la r a tt en ti on t o t he f ac t t ha t a ll l ab o ra to ry r ep or ts a nd l ab o ra to ry p ap er s t ha t

y ou s ub mi t t o b e g ra de d f al l u nd er t he g en er al c at eg or y o f s t u de n t 's o r i gi n a l w o rk . Any a

c a se t h at i t i s o b se r ve d t h at t h e re h a s b e e n d e li b er a te c o p yi n g f ro m a n o th e r s t ud e n t s r e po r t a n d

both reports are handed, both will be considered as act of plagiarism which would be dealt under

the rule of Academic Misconduct as specified in the Student Handbook.

A ss ig n me nt s f or t hi s c ou rs e (P re -l ab R ep or t, P os t l ab R ep or t a nd L ab P ap er) MUST be

s ub mi tt ed electronically via email as a PDF. T he re s ho ul d b e o ne , s in gl e d oc um en t

cont aini ng ans w ers , t abulat ed dat a, pl ot s, s am pl e cal cul at ions , etc. N o h a n d- w ri t te n a s si g nm e nt s

w il l b e a cc ep te d. S am pl e c al cu la ti on s a re m us t a nd n ee d t o b e t yp ed i n M ic ro so ft W or d

e q u at i on e d it o r ( o r f o rm u la e d it o r i n O p en o ff i ce w o rd p r oc e ss o r o r e q ua t io n e d it o r i n G o og l e

D o cs ). P l ot s f r om s p re a ds h ee t s o ft w ar e ( E xc e l o r G o o g l e S h e e ts ) s h o u ld b e p a st e d i n t o

t he w or d p ro ce ss or d oc u me n t ( Wo rd o r G oo gl e D oc s , etc) b ef or e c re at in g a s in g le P DF

d o c um e nt f o r s u b m is s io n . Document Margins ( L ef t 1 , R ig h t 2 . 5 , T o p a nd B ot to m 1 ) . Line

Spacing 1.5.

Writing the Paper

G en er al g ui de li ne s a re g iv en b el ow . S ee e xp er im en t a ss ig ne d f or t he l ab or at or y p ap er f or

specifics on content of sections - Theory, Experimental, Results, and Discussion.

S u m ma r y ( a pa r ag r ap h or so )

( Th e s um ma ry o f a p ap er s er ve s s ev er al p u rp os es . O ne i s t o g iv e t he r ea d er a b ri ef i nt ro du c ti on

o f w h y t h e w o rk w a s d o n e . A l s o i t s h ou l d g i v e a v e ry b r ie f o v e r v ie w ( e x e c ut i ve s u mm a ry ) o f t h e

m aj or f in d in g s o f t he w o rk . I n t he c a se o f t he t ea ch in g l ab , t he s um ma ry s ho u ld a ls o h e lp t he

m ar ke r t o d et er mi ne t he w ri te r' s u n de rs ta n di ng o f t he m ai n t hr us t o f t he l ab e xp e ri me nt w hi le

again summarizing the results that were obtained.)

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Theory

Experimental

Results

Discussion

Conclusions

A c o n cl u si o n s h ou l d b r ie f ly s u mm a ri z e t h e k e y f i nd i ng s r e po r te d i n t h e D i sc u ss i on s e ct i on a n d

s ug ge st io ns f or t he f ut ur e w or k. B as ic a ll y t he C o nc lu si on i s a s ta te me n t o f t he i nf or ma ti on

o b ta i ne d w h at w a s f o un d o u t. A c o mm o n e r r o r i s t o p u t t o o m u c h i n f or m at i on i n t h e c o n cl u si o n,

w hi ch r ea ll y b el on gs i n t he d is cu ss io n . I f y ou r c o nc lu si on i s m or e t ha n a p a ra g ra p h, i t s h o ul d

really be in the discussion.

References

Appendices

Appendix 1 should contain all carbon copies of the data pages from the Lab Notebook.

A pp en di x 2 s ho ul d c on ta in t he o ri gi na l o r g oo dq ua li ty , p ho to co pi es o f t he r ec or de r o r

c o mp u te r o u tp u ts . T he se s ho ul d b e t ap ed o r p a st ed o nt o 8 x 1 1 .5 i nc h p a p er . N ev e r i n cl ud e a

long partial roll of recorder or integrator output with the report!

Appendices 1 & 2 ( c ar bo n c o pi es , r ec or de r o ut pu ts , e tc . ) c a n b e s ca n ne d a nd i nc lu de d i n t he

w or d d oc um en t a s i ma ge s. U se a pp ro pr ia te o pti on s o n t he d esk to p sc an ne r o r ( on th e

s ma rt ph on e a pp ) t o l im it t he i ma ge s iz e ( & s o PDF d o cu me nt f il e s iz e) . K ee p P DF d o cu me nt

file size 2 Mb.

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A ss ig n me nt s f or t hi s c ou rs e (P re -l ab R ep or t, P os t l ab R ep or t a nd L ab P ap er) MUST be

s ub mi tt ed electronically via email as a PDF. T he re s ho ul d b e o ne , s in gl e d oc um en t

cont aini ng ans w ers , t abulat ed dat a, pl ot s, s am pl e cal cul at ions , etc. N o h a n d- w ri t te n a s si g nm e nt s

w il l b e a cc ep te d. S am pl e c al cu la ti on s a re m us t a nd n ee d t o b e t yp ed i n M ic ro so ft W or d

e q u at i on e d it o r ( o r f o rm u la e d it o r i n O p en o ff i ce w o rd p r oc e ss o r o r e q ua t io n e d it o r i n G o og l e

D o cs ). P l ot s f r om s p re a ds h ee t s o ft w ar e ( E xc e l o r G o o g l e S h e e ts ) s h o u ld b e p a st e d i n t o

t he w or d p ro ce ss or d oc u me n t ( Wo rd o r G oo gl e D oc s , etc) b ef or e c re at in g a s in gl e PDF

d o c um e nt f o r s u b m is s io n . Document Margins ( L ef t 1 , R ig h t 2 . 5 , T o p a nd B ot to m 1 ) . Line

Spacing 1.5.

Y o u n e e d t o su b mi t a s i ng l e PDF document.

F il en a me s yn ta x s ho u ld i nc lu de e xp e ri me nt n a me , s ec ti on #, t ea m# a nd y o ur l as t n a me i n

t he f il en am e. P le as e s ee e x am pl e s ho wn b el ow , n o te a sp ac e i nt en ti on a ll y i nc lu de d

in-between syntax terms.

F i l en a me s y n ta x i s v e r y i m p o rt a n t f o r s u c ce s s fu l s u b mi s s io n o f p r e l a b r e p o r t , p o s t l a b

report and of lab paper.

Please NoteY ou w il l n ot b e n ot if ie d a b ou t i nc o rr ec t s yn ta x, a nd s ub mi tt ed r ep o rt /p a pe r P DF f il e w it h

incorrect syntax will not be saved in the system and so it will not be graded.

Please email Pre-lab Report to to the Lab Instructor ([email protected])

Please name PDF document as:

For example: GA1 Pre S1 T1 Sandberg

Please email Post Lab Report to the Lab Instructor ([email protected])

For example: GA1 Post S1 T1 Sandberg

Please email Lab Paper to the Lab Instructor ([email protected])

Please name PDF document as:

For example: GA20 Paper S1 T1 Sandberg

Please dont add any other word, such as Final or Lab Report to the filename syntax.

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Lateness Policy and Lab Preparedness

a. Pre-lab Report

P r e- l ab R e p or t i s m a nd a to r y a n d n e e ds t o b e s u bm i tt e d e l e c tr o ni c al l y ( P D F d o c u me n t) t o t h e l a b

instructor at least TWO days prior to the scheduled experiment.

b. Post lab Report

A ft er t he e xp e ri me nt i s c o mp le te d, r ep o rt i s d u e i n t he f ol lo wi ng w ee k . E le c tr on ic c op y ( PD F

document) of the Lab Report is due on:

10. For Monday/Wednesday Section, report is due on Wednesday at 10 am.

11. For Tuesday/Thursday Section, report is due on Thursday at 10 am.

I f t he l ab r ep or t i s l at e, t he re w il l b e a c u mu la ti ve 1 0 p oi nt s d ed uc ti on p e r d a y t he l ab r ep o rt i s

overdue.

A lo ng w it h t he l ab r ep or t y ou n ee d t o s ub mi t c ar bo n c op ie s o f y ou r n ot eb oo k p ag es . T ho se

copies need to be turned in on the day the lab report is due.

c. Lab Paper

E l ec t ro n ic c o py (PDF d o cu me nt ) o f t he L ab P ap er i s d ue o n t he d ay a nd t im e s pe ci fi ed i n t h e

syllabus. Lab Paper will not be accepted if not received by the time it was due.

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Using Analytical Balances

A n al y ti c al b a la n c es , e s pe c ia l ly t h e f o ur o r f i ve p l ac e , d i gi t al o r s u bs t it u ti o n b a la n ce s , a r e c a p ab l e

o f m ea su ri ng t he w ei gh t o f a n o bj ec t t o 0 .0 00 1 o r e ve n 0 .0 00 01 g , i .e . ( 0. 1 m g o r 0 .0 1 m g) .

T he se b al an c es i f p ro pe rl y c a li br at ed a nd m ai nt ai ne d a re p os si bl y t he m os t a cc ur at e a nd

p r e ci s e m e as u r in g i n s tr u me n t f o un d i n a n y l a b or a t or y. W he th er t ho se b a la n ce s m i g ht b e i n

a n a ly t ic a l, p h y si c al , a d v an c e d i n o r ga n ic a n d o r ga n ic a n d w h e th e r t h ey m i gh t b e i n a c a de m ic o r

in such industrial laboratories as: biotechnology, forensic, pharmaceutical or polymer laboratory.

H en ce i t i s i mp e ra t iv e t ha t o u r s h ar ed a na l yt i ca l b a la nc e s b e k e pt i n e x ce l le n t o p er at i ng

condition. I s h ou l d b e n o te d t h at e a c h b a la n c e i n t h e A d v a n ce d C h e m is t ry C o u r se s o f t h e D e p t.

o f C he mi st ry o f U Co nn i s c he ck ed d ail y b y a m em be r o f th e t ea ch in g s ta ff f or i ts p ro pe r

o p e ra t io n a n d g e n e r al c l ea n li n es s . A l so e a c h y e a r , a n o u ts i de b a la n ce s e rv i ci n g c o m p a ny i s h i re d

to come in to properly service and if necessarily perform major repair on each balance

I t i s a b so l ut e ly i mp er a ti v e t h at e a ch s tu d en t n e ed s t o f i rs t h e ar I nt ro d uc t or y B al a nc e

T al k a nd d o t he i nt ro du ct or y a bo ut f iv e m in ut e w ei gh in g e xp er im en t c on du ct ed b y a

q u a li f i ed l a b or a t or y i n s tr u c to r o r t e a ch i n g a s s is t a nt . T h en e a c h s t u d e n t n e e ds t o a d h e r e t o

t he r ul es t ha t a re g iv en b el ow . R e p e a t e d f a i l u r e t o d o s o , a f t e r h a v i n g r e c e i v e d a c l e a r w a r n i n g

f r om t h ei r p r op e r t e ac h in g s t af f m e mb e r, w i ll c a u se t h at s t ud e nt t o b e a s si g ne d t o d o w e i g h ti n gs

o n t h e o l de r s u bs t it u ti o n b a la n ce , ( w hi c h t a ke s a b ou t 2 . 0 m i n. ) t o a c c om p li s h t h e s a m e w e ig h in g

m ea su re me nt t ha t o th er wi se c ou ld b e d on e o n t he n ew er d ig it al b al an ce s ( wi th in a bo ut 3 0

seconds).

( No te t he se s ub st it ut io n b al an c es a re j us t a s a c cu ra te b ut p e rh a ps n ot a s r ep ro d uc ib le a s t he

n ew er d ig it al b al an ce s) . A nd a s i s e vi de nt t ak e a t l ea st f ou r t im e l on ge r t o a ch ie ve t he s am e

weighing.

General Rules

1 . N o o ne m ay u se a b al an ce w it ho u t f ir st h ea ri ng a n i n tr od uc to ry b a la n ce t al k g iv en b y a

laboratory instructor or teaching assistant.

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2 . U se o nl y t h e b al an c e t o w hi ch y ou a re a ss ig n ed . T h is m us t b e d on e e ve n i f th e a ss ig ne d

balance is in use by another assignee at this particular time. (Remember it usually takes

w it hi n 3 0 s ec on ds . t o a cc om pl is h o ne w ei gh in g o r o nl y a m at te r o f a f ew m in ut es t o

c o mp le te a s er ie s o f w ei gh in gs ). P o st ed n ea r t he b a la n ce w il l b e a l is t o f t h os e s tu d en ts

that have been assigned to use that particular balance for the current semester.

3 . I f t he re s ee ms t o b e a p ro b le m w i th t he b al an c e, r ep or t i t i mm ed ia te ly, t o t h e i n s t r u c t o r o r

teaching assistant. Do not use another balance, unless instructed to do so.

4. It is imperative that you keep the balance and the immediate area around the

balance clean! C le a n u p a ll c h em ic a l s pi ll s a n d e xc e ss c he mi ca l a ft er e ac h u s e o f t he

balance. Do not leave old Kimwipes or crumpled papers on the balance table.

W he n t he b al an ce s a re n o t i n u se , t he b a la n ce s ho ul d b e a l w ay s t u rn ed -o ff a n d i n t he c as e o f t he

substitution balances the beam arrested, all weights on zero and the doors closed.

Please

U se e le ct ro n ic b al an c e c ar ef ul ly a s i t i s a c a li br at ed & e xp e ns iv e i ns tr um en t. T o p re v en t

c o rr o si o n, b e c a re f ul n o t t o s p il l C h e m ic a ls o r W a te r . F o r m o r e i n f or m at i on , p l e a se s e e: P a g e

3 1, Q ua nt it at iv e C he mi ca l A na ly si s, e di ti on 8 th b y D an ie l H ar ri s, W . H . F re em an a nd

Company NY.

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GA1 Analytical Techniques and Measurements

T hi s f ir st l ab or at or y e xe rc is e h a s t wo p ri ma ry g o al s. T h e f ir st g oa l i s t o g i ve y o u a c h an c e t o

practice the classical techniques of weighing and of using volumetric glassware. No matter how

s o ph i st i ca t ed a n a n al y ti c al m e th o d i s , o n e m u st s t il l b e gi n b y w e ig h in g a s t an d ar d m a te r ia l a n d

u s ua l ly d i ss o lv i ng i t i n a n a p p ro p ri a te s o lv e n t i n v o l um e tr i c g l as s wa r e. F o r m u c h o f a n a l y ti c al

c h e mi s tr y , t h e a c c ur a cy o f t h e e n ti r e a n a ly s is d e p en d s o n t h e a c c ur a cy t o w h i ch t h e s t an d a rd ( o r

s ta nd ar ds ) a re c om pa re d. T he s ec on d g oa l i s t o i nt ro du ce a nd u ti li ze c er ta in c on ce pt s o f

s t at i st i ca l t r ea t me n t o f d a ta . C a re f ul l y o b t a in e d r e s u lt s a r e u s el e ss u n le s s t h e i r v a l u es a n d t h e i r

l im it at io ns a re k no wn . T he f ol lo w in g s ta ti st ic al c on c ep ts a re i nt ro d uc e d i n t hi s l ab o ra to ry

e x er ci se : a c cu ra c y a nd p re c is io n ( ab so lu te a n d r el at iv e) e st im at io n o f e rr or ( de vi at io n )

propagation of error significant figures Gaussian (normal) distribution average (mean)

median standard deviation and confidence interval.

There are three parts to this experiment-

1 . U se o f t he A na ly ti ca l B al an ce

2 . C a li br at io n o f V ol um et ri c G la ss wa re

3 . D e te r mi n at i on o f t h e D e n si t y o f A n ti f re e z e

F il l- in s he et s, l ab el ed F 1 t o F 4 w il l b e p ro vi de d i n t he l ab ( a ls o i nc lu d ed a t t h e e nd o f t h i s

e x pe ri me nt al w ri te -u p) . W he n y o u h a ve c om p le te d t he d at a c ol le c ti on , t he se s he e ts a n d a ny

s up pl em en ta ry c al cu la ti on s he et s m ay b e t ak en h om e, a tt ac he d t og et he r a nd h an de d i n f or

m ar ki ng w he n y ou h av e c om pl et ed e ac h s ec ti on . S t ar t in g w it h t h e s e co nd e xp e ri me nt , a l l

l ab or at or y d at a i s t o b e r ec or de d i n t he l ab or at or y n ot eb oo k a t t he t im e t ha t t he d at a i s

c o l le c t ed . L o se s h e et s o f n u mb e rs w i l l n o t b e a l l ow e d! T h e l a b o ra t o ry n o t eb o ok s t a ys i n t h e

l ab or at or y a t a ll t im es ( th is w il l b e c he ck ed ), b ut t he c arb on c op ie s o f t he d ata f ro m th e

notebook may be taken from the laboratory and used in preparing the laboratory report.

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Use of the Analytical Balances

T he re a re t hr ee t yp es o f a na ly ti ca l b al an ce s a va il ab le f or u se i n t hi s l ab or at or y: t he d ig it al

( el ec tr on ic ) b al an ce , a t op l oa di ng b al an ce a nd a s im pl e t ri pl e b ea m b al an ce . I n c er ta in

i ns ta nc e s, t he l es s p re ci se ( an d q ui ck e r) t op l oa di ng o r t ri pl e b e am b al an c es s ho u ld b e u se d.

H o we v e r, s i nc e e v e ry a n a ly s is i n vo l ve s a t l e as t o n e , a c cu r at e w e ig h in g s t ep , i t i s e ss e nt i al t ha t

you are able to use the analytical balances accurately and reproducibly

T hi s e x pe ri me n t w il l g iv e y o u p ra ct ic e i n u si ng a ll t hr ee o f t h e b al an ce s. E ac h b a l an c e h a s a n

i n he r en t a c c ur a cy ( t he n u m be r o f s i gn i fi c an t f i gu r es t o w h ic h y o u f e e l c o n f i de n t i n r e po r ti n g t h e

w ei gh t m ea su re d b y e a ch b al an ce ) and a p re ci si on ( or r ep li ca te v a lu e t ha t y ou o bt ai n i f y ou

c o n ti n ue d t o w e ig h t h e s a m e o b je c t s e v e r al t i me s ). I n m o st c a s e s, i t i s a s su m ed t h a t y o u r e - ze r o

t h e b a la n c e b e t w ee n e a ch s u bs e qu e n t w e i g hi n g. E v e n w it h t h e m o s t e x pe r t u s e, t h e s a m e o b j e ct

w il l n o t n ec e ss ar il y w ei gh t he s am e a mo u nt e ac h t im e t ha t i t i s w ei gh ed . T h e b e st v a l ue f or t h e

w ei gh t o f t he o b je c t i s g en e ra ll y c o ns id er ed t o b e t he a ve ra g e v a lu e.Precision ( devi at i on) i s t he

m ea su re o f t he v ari at io n a mo ng re pli ca te me asu re me nt s. T he i nh er en t p re ci si on ( or

r ep ro d uc ib il it y) o f a b al an c e c an b e e x pr es se d b y e it he r a n a bs ol ut e d ev ia ti on o r a s ta nd a rd

deviation.

A s m o re a n d m o r e t r ia l s a r e m a de , t h e p r e c is i on i m pr o ve s a n d t h e m e an v a lu e g e n er a ll y b e c om e s

a b et te r a nd b et te r e st im at e o f t he t ru e v al ue . H ow ev er , good precision a l on e d o e s n o t i n su r e

good accuracy! S y st e ma t ic e r ro r s c a n o c c ur w h ic h c a u se t h e e x p e r im e n ta l v a lu e t o d e vi a te f r om

t he t ru e v al ue . T he re a re m an y k in ds o f systematic or determinate e r ro rs , b ut t he y a ll c an , i n

principle, be identified and then be either eliminated or corrected for. For example, one source

o f a d et er mi na te e rr or i s i na cc ur at e w ei gh ts i n t he b al an ce i ts el f. I n p ri nc ip le , t hi s c ou ld b e

e l i m i n a t e d b y m a k i n g s u r e t h a t t h e a b s o l u t e w e i g h t s a n d v o l u m e s o f t h e s o l u t i o n m e a s u r e d a r e a l l

a c c ur a te o r t r ac e a bl e t o a c ce p ta b le s t an d a rd s . I n t h i s e x p er i me n t, e x p er i me n ta l c a us e s, s u ch a s

t ou ch in g t he o bj ec t t o b e w ei gh ed w it h o n e s h a nd s, w hi ch m ay b e d et ri me nt al w he n u si ng t he

most precise analytical balances, will be investigated.

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a. Precision of Various Balances

T he re a re t hr ee t yp es o f b a la n ce s i n t he a n al yt ic a l l ab : t he d ig it al b a la n ce ( DB ), t he t op l oa d in g

( TL B) , a nd t he t ri pl e b ea m b al an ce ( TB B) . A w ei gh in g b ot tl e a n d i ts c ap , b o th a re i n y o ur

l o ck e r t o p s h el f a r e n e e de d f o r t h is p a r t o f e x pe r im e nt . M a ke s u r e t h a t y o u p i c k -u p t h e s e o b je c ts

o n ly w i th c r uc i bl e t o ng s o r t w ee z e rs s o n o ne o f y o ur f i ng e r s g r e a se o r m o i st u re i s p i c k ed - up o n

t he o b je c t b et we e n w ei gh in gs . S in ce , y o u w il l b e d oi ng e xp e ri me nt w it h y o ur l ab p ar tn er , j us t

o n e w ei gh in g b o tt le & a c a p b e t we en t wo o f y ou i s r e q ui re d, s o e a c h o ne w il l h a v e e xa c t s a me

data.

W e ig h y o u r o b je c t o n e a c h o f t h e t h re e d i f f er e nt t y pe s o f b a la n c e, c o n se c u ti v el y . R e co r d e x a c tl y

t he w ei gh t ( to t he p ro p er n um be r o f s ig ni fi ca nt f ig u re s) y o u o bt ai ne d b y r ea d in g t he b a la n ce s

g ra du at ed s ca le . M ak e s ur e y ou r em ov e t he o bj ec t a nd r e- ze ro t he b al an ce b et we en e ac h

successive weighing.

R e -w e ig h t h e o b je c t a t o ta l o f t h re e t i m e s o n e a ch b a la n ce . M a ke s u re y o u r e m ov e t h e o b je c t a n d

re-zero the balance between each successive weighing.

b. Use of the Digital Balance

I n t hi s s ec ti on , y ou w il l f ir st w ei gh a w ei gh in g b ot tl e a nd t he n i ts l id u si ng o nl y t he d ig it al

balance. Then you will weigh both together on the pan at the same time. The sum of the first

t wo w ei gh ts s ho u ld b e t he s am e w i th i n t h e p r ec i si o n o f t h e b a la n c e. If y ou a re st ill n ot a bl e t o

r e du c e t h e e x p er i me n ta l d i ff e re n ce s b e tw e en t h e t w o w e ig h in g s, a f te r a s e co n d c h e c k in g , p l e a se

consult the laboratory instructor and/or teaching assistant.

1 . H an d li ng i t w it h c ru ci bl e t on g s, d et er mi ne t he w ei gh t o f a c le a n, d ry w ei gh in g b ot tl e t o

the nearest 0.1 mg (0.0001 g)

2. D et er mi ne t he w ei ght of the l i d t o the near est 0. 1 m g

3. Determine the total weight of the bottle plus the lid to the nearest 0.1 mg.

4 . F in d t he s um o f t h e r e su lt s o f # 1 a n d # 2 a n d c om pa re w it h # 3 . T h e t wo s ho ul d a g re e t o

within 0.5 mg.

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c. Sources of Determinate Weighing Errors

1 . R ol l t he w ei gh in g b ot tl e i n y ou r h an d, h an dl e i t, a nd f in ge r i t. T he n r e- we ig h i t a nd

compare it with the previous result.

2 . W ip e t he w ei gh in g b ot tl e w it h a K im wi pe . W ei gh i t a n d c om pa re w it h t h e p re vi ou s

results.

3 . B re at he o n t he w ei gh in g b o tt le w ei gh i t a g ai n a nd c om pa re t hi s r es ul t w i th t he p re vi ou s

results.

4 . I ni ti al t he w ei gh in g b ot tl e w it h a # 2 p en ci l o n t he g ro un d g la ss p at ch ( do n ot u se i nk i t

cannot be removed). Re-weigh and compare with previous results.

P la ce t he w ei gh in g b ot tl e i n a d ry in g o ve n f or a bo ut t hr ee m in ut es , j us t e no ug h t o w ar m i t.

R em ov e t he b ot tl e f ro m t he o ve n w it h t on gs a n d r e- we ig h i t i mm ed ia te ly w hi le i t i s s ti ll w ar m.

F ol lo w t he c ha ng e i n t he a pp ar en t w ei gh t f or s ev er al m in ut es . R ec or d t he w ei gh t e ve ry 3 0

seconds.

Please

U se e le ct ro n ic b al an c e c ar ef ul ly a s i t i s a c a li br at ed & e xp e ns iv e i ns tr um en t. T o p re v en t

c o rr o si o n, b e c a re f ul n o t t o s p il l C h e m ic a ls o r W a te r . F o r m o r e i n f or m at i on , p l e a se s e e: P a g e

3 1, Q ua nt it at iv e C he mi ca l A na ly si s, e di ti on 8 th b y D an ie l H ar ri s, W . H . F re em an a nd

Company NY.

Calibration of Volumetric Glassware

S in ce t he e xa c t v o lu me o f a p ie ce o f v ol um et ri c g la ss wa re i s n o t n ec e ss ar il y i de nt ic al w it h t ha t

printed on it, glassware must be calibrated when it is to be used in extremely accurate

q u an ti ta ti ve w or k. G la ss wa re c a li br at io n i s m os t o ft en p er fo rm ed b y w ei gh in g t he a mo u nt o f

w at er c on ta in ed b y o r d el iv er ed f ro m t he g la ss wa re . K no wi ng t he d en si ty o f w at er a t t he

appropriate temperature, one may calculate its actual volume.

1 . C al ib ra ti on o f a 2 5 m L P ip et

2 . C a li br at io n o f a d ig it al P ip e t

In this experiment, a pipet (nominal volume 25 ml) and a digital pipet will be calibrated.

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a. Buoyancy Corrections

O b ta i ni n g t h e t r ue w e ig h t o f w a te r d e li v er e d f r om v o lu m et r ic g l as s wa r e r e q u ir e s w e i g hi n g t h e

s am pl e, a nd t he n m at he ma ti ca ll y c o rr ec ti ng f or t he f ac t t ha t t he b a la n ce c an g iv e a t ru e w ei gh t

o n ly f o r m a t e ri a ls h a v in g t h e s a m e d e ns i ty a s t h e w e ig h ts . T h is d i ff e re n c e i n d e n si t y c a u se s t h e

a p pa re n t w ei gh t o f t he w at er t o b e l es s t ha n t he a c tu a l w e i gh t s in c e a c e rt ai n a mo un t o f a ir h as

been displaced by the item being weighed. For most solids, no correction is required because the

d en si ty o f t he s ol id i s s uf fi ci en tl y s im il ar t o t he d en si ty o f t he w ei gh ts . B ut , f or l iq ui ds a nd

gases, however a buoyancy correction must be made, when high accuracy is desired.

T h e e q u at i on b e lo w i s a n e x p re s si o n f o r t h e c o r re c te d w e ig h t o f t h e o b j e ct i n a v a cu u m , b a s ed o n

i ts m ea su re d, a pp ar en t, w ei gh t i n a ir . D er iv at io n o f t hi s e qu at io n m ay b e f ou nd i n v ar io us

a n al yt ic al t ex ts . T he w ei gh t o f w at er i n v ac u um , o r t he c or re c te d w e i gh t, s ho ul d b e u se d f o r t h e

calculations of glassware volume.

Wv =D Dw o

W {(D D )D }o w o a+Wo

WV

= Weight of Water in Vacuum

WO

= Weight of Object (Water) in Air

D0

= Density of Object (Water)

Da

= Density of Air

DW

= Density of Weight (8.00 g/mL)

DO

, t he d en si ty o f w at er , i s t em pe ra tu re d ep en de nt . V al ue s a t v ar io us t em pe ra tu re s m ay b e

f ou nd i n T ab le 2 - 7 f or m ore d eta il s re fe r t o th e t ex t, D . C . H ar ri s, Quantitative Chemical

Analysis , 7th edition, Chapter 2, page 32 7th Edition, page 42, page 42.

Temperature (0C) Density of Air (g/mL) Da

, the density of air at room

temperature may be found in the adjacent

table taken from the Handbook of Chemistry

and Physics, 52nd edition, 1971-72, The

Chemical Rubber Co., Cleveland, OH.

To obtain the density of air at other

temperatures, calculate that value assuming a

simple linear progression of the data found in

the above table.

20 0.001184

21 0.001180

22 0.001176

23 0.001172

24 0.001168

25 0.001164

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Precaution

B ef or e b e gi nn in g t he c al ib ra ti on o f g la ss wa re , b e s ur e t ha t t he g la ss wa re i s s cr up ul ou sl y

c l ea n . C l ea n g l as s wa r e s h ow s n o w a t e r d r op l et s w h e n f i ll e d w i th w a te r a n d t h e n e m p t ie d . T o

c le a n, f ir st t ry w as hi ng t he g la ss wa re w it h a v e ry d il ut e s ol ut io n 1 -3 p e r c en t o f d et er ge nt i n

w at er . F ol lo w b y r in si ng e ac h p ie c e o f g la ss wa re w it h a b ou t f iv e s uc c es si ve r in se s o f t ap

w a te r t h en w i th t h re e r i ns e s o f t h e l a b o ra t or y d e i o ni z e d w a te r . I f t h i s d o es n o t w o rk a n d t h er e

s t il l r e ma i ns d r op l et s ( c al l ed h a ng ) o n t h e i n si d e o f t h e g l as s wa r e, a s k th e i n st r uc t or a n d/ o r

t e ac h in g a s si s ta n t t o c l ea n th e g l as s wa r e w i th t h e a v a il a bl e , l o w- e nv i ro n me n ta l i m pa c ti n g

detergent.

b. Direct Calibration of 25 mL Pipet

P ro pe r p ip ett in g w il l b e d em on st ra te d in o ne o f t he la bo ra to ry b rie fin gs. I t i s h ig hl y

r e co m me n d ed t h at y o u p e rf o rm s e ve r al p r ac t ic e r u ns i n cl u di n g c h e ck i ng t h e w e ig h t d e li v er e d

from subsequent 25 ml pipet deliveries. Practice pipetting with the 25 ml pipet as follows:

Precaution

D o n o t t ak e d ei on iz ed w at er f ro m t he t ap , s in ce i t w il l c h an g e t em pe ra tu re a s t h e e x pe ri me nt

proceeds. From one of the large jugs sitting at the end of several of the benches, fill a 400 mL

beaker with about 300 mL of deionized water that has already been stored at room

temperature. Measure and record the temperature of the water throughout the experiment.

Please

A t o th er t im es d o n ot u se t hi s t em pe ra tu re -e qu il ib ra te d w at er a s i t i s u se d a s a b ac k- up

d e io n iz e d w a te r s u p p l y w h e n t h e h o us e w a te r s u pp l y r u n s d r y . T h es e l a rg e j u gs t h at c o n ta i n

the temperature-equilibrated water are very difficult to refill.

1 . F il l t he p ip e t p a s t t he c al ib ra ti on m ar k w it h d ei on iz ed w at er u s i ng a p ip e t b ul b. R em ov e

t he b ul b, a nd b y m an ip u la ti ng t he i nd ex f in g er , n o t t he t hu mb , a dj us t t h e b o tt om l ev el o f

the meniscus until it coincides exactly with the calibration mark.

2 . W hi le c a re fu ll y m ai nt ai ni ng t he p ip e t i n a v e rt ic a l p os it io n, t ou ch t he t ip o f t h e p i pe t t o a

glass surface to remove any extra droplet of water adhering to the outside of the tip.

T o e mp ty t he p ip et , r em ov e t he i nd e x f i ng e r a n d l et t he w at er f lo w i nt o a g la ss c o nt ai ne r. L et t he

pipet drain for a minimum of 10 seconds after the free flow of water from the pipet has stopped.

I n f a c t i t i s u s u a l l y s u g g e s t e d t o a l l o w f o r a 1 s e c o n d w a i t f o r e a c h m L o f v o l u m e d e l i v e r e d . T h e n

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t ou ch t he t ip o f t he p ip et t o t he w al l o f t he c o nt ai ne r t o r em ov e a ny h a ng in g w at er d ro p s f r om t he

tip. H ow ev er , d o n o t f or c e o ut b y e i th e r b lo w in g o r s h ak i ng any w a t er t h atr e m a i n s i n t h e

tip. T he r em a in in g w at er i n t he t ip h as b e en t ak en i nt o a c co u nt i n t he d e si gn o f t h e p i pe t b y t he

m an uf ac tu re r. T he t ot al v ol um e d el iv er ed b y t he se T D ( to d el iv er ) p ip et s t he n b ec om es

r ep ro d uc ib le . B ut o f c o ur se , i t m ay n ot b e c o mp le te ly a cc u ra te ! W he n p ip et ti ng t ec hn iq ue h a s

been satisfactorily mastered, the calibration can be started.

W ei gh ( u si n g t h e d i gi t al a na l yt i ca l b al a nc e) a c l ea n 1 2 5 m L E r le n m ey e r f l a s k e q u i pp e d w i th

t he p ro p er r ub be r s to pp er t o t he n e ar es t m il li gr am ( 0. 0 01 g ). Note: a c c u r a c i e s o f 0 . 1 m g a r e n o t

n e ed ed f or t he g la ss wa re c al ib ra ti on s. A lw ay s h a n dl e t h e f la sk w it h t o n gs o r a s tr ip o f p a p er .

T he f la sk n ee d n ot b e d ry o n t he i ns id e, o nl y o n t he o ut si de , b ut t he i ns id e n e ck i n w h ic h t h e

rubber stopper in inserted must be kept dry. (Why?)

C ar ef ul ly , t ra n sf er a n a li qu ot ( th e c on te nt s) o f t he 2 5 m L p ip e t i n to t he f la sk h o ld in g t he p ip e t

v e rt ic a ll y w it h i ts t ip w el l i ns id e t he f la sk t o a v o id w at er s pl as hi ng o n to t he n ec k , o r o ut . I t i s

i mp o rt an t t ha t t he n e ck o f t he f la sk r em ai n d ry . A s i n t he p ra c ti ce r un s, a l l ow t h e p i p et t o d ra in

t ho ro ug hl y. T he n to uc h th e t ip o f th e p ip et t o t he s id e o f th e f la sk . Wi th dra w t he p ip ett e

(pipetting should be performed at the work table and not in the Balance Room). Weigh the flask.

R e p ea t b y w e ig h in g a d d it i on a l a l iq u ot s o f w a te r d e li v er e d i n t o t h e E r l e n me y e r f l a sk s u bs e qu e n t

a li qu ot s m ay b e a dd ed t o t he v ol um e o f w at er a lr ea dy i n t he f la sk u nt il t he c ap ac it y o f t h e

balance is exceeded.

P er fo rm a t l ea st f ou r t ri al s o r e no ug h t o o bt ai n a p re ci si on i n t er ms o f r el at iv e a ve ra ge

deviation of 1 ppt (part per thousand) or 0.1%.

c. Direct Calibration of a Digital Pipet

T hi s s ec ti on i s d e si gn ed t o g iv e y o u p r a ct ic e o n u si ng a d ig it al p ip et . P le as e s ee t he I ns tr uc to r

a b ou t w hi ch p ip et t o u se . O bt ai n t he p ro p er t ip a nd p ra ct ic e t he v o lu me d e li ve ry , m ak in g s ur e

t ha t t he l iq u id d ro p s d o n o t l e a k f r o m t h e t ip d ur in g t ra n sf er . I f t h i s o c c ur s i t u su a ll y i nd ic a te s

t ha t t he t ip i s n ot t ig ht ly s ec ur ed o r t ha t t he i nn er s ea l o f t he p ip et i s n ot l ub ri ca te d o r n ee ds

replacing.

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I nt o t he w ei gh ed E rl en me ye r f la sk , c a re fu ll y d el iv e r t he f ul l c on te nt s o f t he d ig it al p ip e t. O n

F il l- In s he et , m ak e s ur e t ha t y ou r ec or d t he n am e o f t he m an uf ac tu re r o f t he d ig it al p ip et ,

w he th er i t h a s f ix ed o r v ar ia b le v ol um e d el iv er y, a nd t he f ul l v ol um e d e li ve ry t ha t y ou u se d .

Obtain the weight of the water delivered.

Repeat this procedure at least four times in order to obtain a meaningful mean value and

appropriate precision.

Determination of the Density of Antifreeze

T h is p a rt o f t h e l a b o r at o ry e x e rc i se u t il i ze s t h e a n a l y ti c al b a la n ce a n d t h e c a li b ra t ed , 2 5 m L p i pe t

to determine accurately the density of commercial antifreeze.

A pa rt f ro m c al ib ra te d 2 5 m L p ip et , y ou a ls o n e e d a 2 50 m L b e a ke r a n d a 1 2 5 m L f la sk a l l t h re e

need to be dry, free of any traces of water.

Measure out into a 250 ml beaker about 100 ml of antifreeze.

F ir st , c ar ef ul ly r in se y ou r 2 5 m l p ip et a t l ea st t hr ee t im es w it h s ma ll v ol um es o f t he

a n ti f re e z e s a mp l e. P l ea s e c o ll e ct a l l r i n si n g a n d e x ce s s a n t if r ee z e i n t h e s a m e b e a k e r t h a t

c o n ta i ns a n ti f re e ze s a mp l e. C a re f ul l y d e li v er a r e pr e se n ta t iv e s a mp l e o f t h is a n ti f re e z e

using your calibrated 25 ml pipet into a pre-weighed Erlenmeyer flask.

R e pe at t hi s p ro ce d ur e a n o th e r t h re e o r m or e t i m es i n o r d er t o o b t ai n a m ea n a nd a c le a r

m ea su re me nt o f t he p re ci si on o f y o ur w ei gh t d e li ve ri es . S ub se qu e nt v ol um es o f t he

a nt if re ez e m ay b e a dd ed t o t he o ri gi na l v ol um e f ou nd i n t he E rl en me ye r f la sk . T he

precision should be within 1 ppt (part per thousand) or 0.1%.


1. D ef i ne pr eci si on and accur acy

2 . G iv e f or mu la f or ( a) A ve ra g e D ev ia ti on ( b) R el at iv e A v er ag e D ev ia ti on ( c) S ta n da rd

deviation (d) Relative Standard Deviation.


a. Use of the Analytical Balance

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1. W hi ch balance i s m os t preci s e? W hi ch bal ance i s m os t accur at e? Justify your answer!

b. Weighing Errors

1 . W ha t p re ca ut io ns sh ou ld o ne ta ke to i ns ure t he b es t p re ci si on a nd a cc ur ac y wh en

w e ig h in g a n o b je c t? W h ic h o f t h e a b o v e p r o ce d u re s d o n o t a f f ec t p r e c is i on a n d a c c u ra c y

(if any)? Which have the greatest effect on precision and accuracy?

2 . C om pa re t he s um o f t he w ei gh ts o f a w ei gh in g b ot tl e a nd l id w it h t he e xp er im en ta l

w ei gh t o f t he se t wo o bj ec ts t og e th e r. W ha t i nd iv id u al e rr or s i nv ol ve d i n t h e w ei gh in g

process can you expect? Specifically, how is the weight affected? Clearly explain your

answers in the report that you hand in with this data sheets.

c. Direct Calibration of 25 mL Pipette

1 . F o r e ac h w ei gh t o f w at er , f in d t he w ei gh t i n v ac u um ( co rr ec te d w e i gh t) b y c o r re c ti ng t he

weight in air for the buoyancy of air. Show sample calculations.

2 . U si ng t he d en si ty o f w a te r a t t he e x pe ri me nt al t em pe ra tu re a nd t he c or re c te d w e i gh t o f

the water, find the volume of the pipet.

3. F i nd t he m ean and m edi an ( center m os t ) val ues f or the pi pet vol um e.

4 . F in d t he s ta nd ar d d ev ia ti on o f t he p ip et v ol um e. T o h ow m an y s ig ni fi ca nt f ig ur es t he

a v e ra g e v o lu m e d e l i ve r ed b y y o ur 2 5 m L p i p e t s h o u ld b e r e po r te d ? ( H in t : R e a l R u l e f o r

S i gni fi cant F i gures C hapt er E xper i ment al E r r or i n Q uanti t at ive C hem i cal A nal ysi s

by Daniel Harris).

Remember

A lw ay s u se Re al R ul e o f S ig ni fi ca nt o f F ig ur es w he n r ep or ti ng c al cu la te d m ea n a nd

standard deviation

d. Determination of the Density of Antifreeze

C a lc u la t e s t an d a rd d e vi a ti o n o f t h e d e n si t y o f a n ti f re e z e b y u s i n g t h e c o n ce p t o f p ro p a ga t io n o f

errors. Show sample calculations.

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Datasheets

F1

Name

Section Date

Part 1 - Use of the Analytical Balance

Balance Type Digital Balance Top Loading

Balance

Triple Beam Balance

Manufacturer Mettler Denver/Mettler OHaus

Weighing Mass (g) Mass (g) Mass (g)Trial 1

Trial 2

Trial 3

Mean Mass

Absolute Precision

Average Deviation

Standard Deviation

Relative Precision

Relative Average

Deviation (RAD)

Relative Standard

Deviation (RSD)

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F2

Mass of Weighing Bottle obtained using Digital Balance

Part 1B - Weighing Errors Mass (g)

1 Mass of weighing bottle alone

2 Mass of Lid

3 Sum of 1 & 2 (Mass of Weighing Bottle alone + Mass of Lid)

4 Mass of bottle and lid

5 Difference between 3 & 4 (should agree to within 0.5 mg)

Part 1C - Sources of Weighing Errors

1 Mass of weighing bottle after handling

2 Mass of weighing bottle after wiping

3 Mass of weighing bottle after breathing on it

4 Mass of weighing bottle after pencil mark

5 Mass of hot weighing bottle every thirty seconds

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F3

Part 2 - Calibration of Volumetric Glassware

25 mL Pipet

Temperature of Water = Density of Water =

Weight of water and corrected weight of water delivered from 25 mL pipet

Initial Weight (g)

Final Weight (g)

Actual Weight (g)

Corrected Weight (g)

Calculated volume for the 25 mL pipet

Corrected Volume (mL)

Mean value = Median Value =

Standard deviation = Relative Standard Deviation =

Digital Pipet

Digital Pipet Manufacturer = Fixed or Variable =

Digital Pipet Capacity = Density of Water =

Weight of water and corrected weight of water delivered from the Digital Pipet

Actual Weight (g)

Corrected Weight (g)

Calculated volume for the Digital Pipet

Corrected Volume (mL)


Standard deviation = Relative Standard Deviation =

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F4

Part 3 - Density of Antifreeze

Weight of Antifreeze delivered from 25 mL pipet

Initial Weight (g)

Final Weight (g)

Actual Weight (g)


Standard deviation = RSD =

Mean Volume & Standard Deviation of 25 mL pipet from previous section (F3) =

Antifreeze Density = Standard Deviation* =

* Use propagation of error for calculating

Standard deviation

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Notes on Calibrating Volumetric Flask and Burette (excluded from GA1)

Y ou r 2 50 v ol um et ri c f la sk s ho ul d b e w as he d , t he n r in se d t wi ce w it h s ma ll a mo u nt s o f a ce to n e

a nd l ef t u ps id e d ow n, h an gi ng f ro m a t ri po d, t o d ry f or a bo ut 3 0 m in ut es , s o i t w il l b e r ea dy

when needed.

A n o mi n al 2 5 0 m l v o lu m e tr i c f l as k c a n b e c a li b ra t ed b y a n i n di r ec t m e t h od , w h i c h i s f a s te r t h a n

t he d ir ec t m et ho d , a nd s uf fi ci en t f or o ur p ur po se s. T hi s i s d o ne b y d el iv e ri ng t en a li qu o ts o f

w at er f ro m t he ( sa me ) 2 5 m L p ip et i nt o t h e 2 50 m L v o lu me tr ic f la sk . T he l oc a ti on o f t he b ot to m

part of the waters meniscus corresponding to the total addition of the 10 25 ml pipet additions

i s t h en m a rk e d . I f t h e f l as k i s s u bs e qu e n tl y f i ll e d e x a c t l y t o t h e c a l i b r a t i o n m a r k , t h e n o n e 2 5 m l

pipet full of solution will contain exactly o f t he o ri gi na l a mo u nt o f s ol ut e i n t he s ol ut io n. 110

This is a useful calibration method even if the pipet is not directly calibrated.

B ur et s m ay b e c al ib ra te d a t s pe ci fi c v ol um e i nt er va ls . F o r e xa mp le , t he 5 0 m L b u re ts m i g ht b e

c a li br at ed e v er y 1 0 m l b y c om pa ri ng t he n o mi na l v ol um e o f w at er d e li ve re d ( re ad f ro m t h e

buret) with the actual volume water delivered. The latter is obtained by weighing the water and

d e te rm in in g t he v ol um e f ro m t he d en si ty . Y ou w il l n o t n ee d t o c a l ib ra te y ou r b ur et s b e c au se ,

e xc ep t in t he m ost e xa ct in g w or k, i t is n ot w or th th e ti me i t ta ke s t o d o t he c ali br ati on .

F u rt h er m or e i t h a s b e en g e ne r al l y n o te d t h at b e gi n ni n g a n a l y ti c al w o rk e rs t e nd t o r e po r t l a r g er

errors in the volumes delivered by burets than are actually present.

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GA2 Acid Base Titration

G A2 A ci d- Ba se T it ra ti on i s t he d e te rm in a ti on o f t he p e rc en ta g e o f p ot as si um a c id p h th a la te

( KH P) i n a n i mp ur e s ol id m ix tu re ( th e " un k no wn ") . T he w ea kl y a c id ic K HP , w hi ch i s w at er

s o lu b le , c a n b e t i tr a te d w i th a s o lu t io n o f N a OH w h os e c o n ce n tr a ti o n i s p r ec i se l y, a n d h o pe f ul l y,

accurately known.


~ 0 . 1M N a OH , p h e no l ph t ha l ei n i n di c a to r , p r im a ry s t an d a rd K H P, u n k no w n K H P ( P o t as s iu m

Hydrogen Phthalate)

Standardization of ~ 0.1M NaOH against the Primary Standard KHP

T he p ri ma ry s ta nd a rd K HP w il l b e u se d t o s ta n da rd iz e t he s od iu m h y dr ox id e s o l ut io n. T h e

a mo u nt o f p ri ma ry s ta n da rd K HP u se d f or e a ch t it ra ti on i s d ic ta te d b y t he r eq ui re me n t t o k e ep

t he r el at iv e e rr or , r es ul ti ng f ro m t he r ea d in g o f t he b ur et , a s l ow a s p o ss ib le . S in c e t h e t ot al

precision of the volume reading of the 50 mL buret is 0.04 mL, a volume of 35-45 mL

d e l i v e r e d w i l l r e s u l t i n a r e l a t i v e e r r o r o f a b o u t 1 p p t ( p a r t - p e r - t h o u s a n d , i . e . , 0 . 0 4 / 4 0 . 0 0 X 1 0 0 0 ) .

A ss um in g a n e n d p oi nt i s t o o c c ur u p on t he d e li ve ry f ro m 3 5 t o 4 5 m L o f 0 .1 M N a O H, c al cu la te

t he r an ge i n t he s am pl e w ei gh t o f p ri ma ry s ta n da rd K HP ( FW 2 04 .2 3 ) t h a t s h o ul d b e w ei gh ed

out.

Amount of KHP that will require 40 mL of ~0.1M of NaOH to reach end point

.04L ________moles 204.23 _________ g0 ~ 0.1MNaOH

= _KHP FW

=KHP

P ri ma ry S ta nd ar d K HP i s i n t he d es ic ca to r p la ce d n ea r d ig it al w ei gh in g b al an ce . T o o pe n a

d es ic ca to r, s li de l id s id ew ay a nd d o n ot t ry t o p ul l i t s t ra ig ht u p a s i t i s g re as ed t o m ak e a n

ai r t ight s eal .1

1Page 41, Quantitative Chemical Analysis, edition 8th by Daniel Harris, W. H. Freeman and Company

NY.

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1 . W e ig h o u t f o u r s a m p le s o f p u re , d r y , p r i ma r y s t an d a rd K H P o f k n o w n p u ri t y f a c to r i n t o f o u r,

n u mb e re d 2 5 0 m L E r le n me y e r f l as k s. O n ce w e ig h e d o u t , t h e se m a y b e l e ft , u n d i ss o lv e d b u t

s to pp e re d , i n y ou r l ab b e nc h u n t il r ea d y f o r u s e . B e s ur e t o l ab el t he f la sk s s o t ha t y o u k no w

which sample is in each flask.

2 . T o t he K HP i n t he f la sk , a d d a b ou t 5 0 mL o f d ei on iz ed w at er a n d 2 d ro ps o f p he no lp h th a le in

i nd ic at or . I t w il l b e n ec es sa ry t o w ar m t he s ol ut io n g en tl y t o a bo ut 5 00C a nd s wi rl to

dissolve the KHP.

3 . B ef or e f il li ng c om pl et el y t he 5 0 m L b ur et , f i rs t r i ns e i t t hr ee t im es w it h ~ 5 m L p o r ti on s o f

0 .1 M N aO H s ol ut io n. C a re fu ll y r ea d a nd r ec o rd t he i ni ti al b u re t r ea di ng . N ot e: a l l b u re t

r ea d in gs s ho ul d b e r ea d t o t he n e ar es t 0 . 01 m L. T ak e c a re t o r ea d t h e b u re t p r op er ly . R ef er

to t he p ic to ria l i llu str at io n lo ca te d a t t he e nd o f G A2 s ho wi ng h ow to re ad t he w at er

m en is cu s o f t he 5 0 m L b ur et . N ot e t ha t s ig ni fi ca nt a dd it io na l e rr or i n t he b ur et r ea di ng

occurs if the buret has to be refilled a second time. Why is that?

4 . T i tr a te w i th t h e N a O H s o lu t io n u n ti l J U S T B E FO R E t he f i r st p e r ma n e nt a p p e ar a nc e o f l i g ht

pink color is seen throughout the solution. STOP! At this point, continue the titration by

a d di n g N a OH s o lu t io n d r op w i se o r b y s p li t ti n g d r o p s u n t i l t h e f i r s t p e r m an e n t a p p e a ra n c e o f

a pink color persists throughout the solution for at least 30 seconds.

5 . R ep ea t b y c ar ef ul ly t it ra ti ng t he o th er t hr ee s am pl es . C he ck t ha t t he r el at iv e a ve ra ge

d ev ia ti on o f t he se f ou r t ri al s d o es n o t e xc e ed 2 p pt . I f t he p re ci si on i s t o o p o or , h i gh er t ha n

a bo u t t hr ee p p t. , t it ra te t wo a d di ti on al s am pl es u nt il t he r eq u ir ed p re c is io n i s o bt ai ne d.

Employ the Q-test in an effort to reject the most outlying value.

6 . W ha t i f t he d ei on iz ed w at er u se d t o d i s so lv e t he p ri ma ry s ta nd a rd K HP w er e c o n ta mi na te d

w it h a n i nt er fe ri ng i on ? A ll r es ul ts a re s us pe ct u n le ss a " bl an k" ( co nt ro l) t it ra ti on i s d o ne .

T o m e as u re t h e b l a n k c a rr y o u t a s e pa r at e t i tr a ti o n f o l l ow i ng e x ac t ly t h e s a m e p r oc e d ur e a s

u se d f or t he s am pl e e x ce pt d o N OT a dd t he K HP t o t he E rl en me ye r f l a sk w hi ch i s u s e d a s

t he t it ra ti on v es se l. R ec o rd t he v ol um e o f N aO H r eq ui re d t o r ea c h t he p h en ol ph th al ei n

e nd p oi nt . C he ck t o s ee t ha t t h i s v a l ue i s l e s s t h an 0 . 10 m L ( o r l es s t h a n t wo d r op s) . I f n ot ,

please inform the instructor.

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Determination of Percent KHP in an Unknown Mixture

Y ou n ee d t o w ei gh o ut a mo u nt o f K HP t ha t w i ll r eq ui re 2 5 m L o f s t an d ar di ze d N a O H. A mo un t

of unknown KHP sample required for each trial:

.025L ________moles 204.23 _________ g0 ~ 0.1MNaOH = _ KHP FW = KHP

Assuming KHP purity of ~40%, the amount of KHP to be weighed out for each titration:

= _________ gPurityFactor

KHP __________ gunknown

O b ta i n a n u n k no w n K H P s a mp l e f r o m t h e i n st r uc t or . T h e i n s tr u ct o r w i l l h a v e c o d e d i t w i th y o ur

name. You will re

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