Engineering Chem 24092009

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Engineering Chemistry Lab Manual (I B.Tech Common to All)

Experiment-1

ESTIMATION OF HARDNESS OF WATER BY EDTA

(COMPLEXOMETRY)

Aim: To estimate the hardness of the given Sample water using a standard solution of EDTA.

Apparatus: 100 ml standard flask,

Burette,250 ml Conical Flask,

20 ml Pipette,

& Simple balance with weights,

Chemicals Required: Ethylene di-amine tetra acetic acid (EDTA),

Solo-chrome (EBT) Indicator,Ammonia Buffer solution,

Hard-water & distilled water.

Principle: Hard water which contains calcium and magnesium ions forms a wine red colored complex

with the indicator, Eriochrome Black-T.Ethylene diamine tetra acetic acid (EDTA) forms a colourless stable complex with free metal ion like

Ca, Mg. i.e., Metal + Indicator Metal indicator complex (wine red colour)

When EDTA is added from the burette, it extracts the metal ions from the metal ion-indicator complex

thereby releasing the free indicator. (The stability of metal ion-indicator complex is less than that of the metal ion- EDTA complex, and hence EDTA extracts metal ion form the ion-indicator complex.)

EDTA + Metal indicator complex Metal ion-EDTA + Indicator

(Wine red color) (Blue)

The reactions take place at a pH = 10 and the buffer is made by ammonium chloride and ammonium

solution.

Procedure:

Preparation of standard hard water: Dissolve 1g of pure, dry CaCO3 in minimum quantity of

dil.HCl and then evaporate the solution to dryness on a water bath. Dissolve the residue in distilledwater to make 1 Liter solution. Each mL of this solution thus contains 1mg of CaCO 3 equalent

hardness.

1 mL hard water solution = 1mg of CaCO3 equivalent hardness.

Standardization of EDTA solution: Rinse and fill the burette with EDTA solution. Pipette out

50 mL of standard hard water in a conical flask. Add 10-15 mL of buffer solution and 4 to 5 drops

of EBT-indicator. Titrate with EDTA solution till wine-red colour changes to clear blue. Letvolume EDTA solution used be V1 mL.

Titration of Unknown Hard water: Rinse and fill the burette with EDTA solution. Pipette out 50mL of Sample hard water in a conical flask. Add 10-15 mL of buffer solution and 4 to 5 drops

EBT-indicator. Titrate with EDTA solution till wine-red colour changes to clear blue. This marks

the end point of the titration. Repeat the titrations for constant titer values.Let volume of EDTA solution used be V2 mL.

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SV Group of Institutions 1




Titration of Permanent hardness: take 250 mL of the water sample in a large beaker. Boil it. Till thevolume is reduced to about 50 mL, filter it, wash the precipitate with distilled water, collecting filtrate

and washing in a 250 mL measuring flask. Finally makeup the volume to 250 mL with distilled water.

Rinse and fill the burette with EDTA solution. Pipette out 50 mL of Boiled hard water in a conicalflask. Add 10-15 mL of buffer solution and 4 to 5 drops EBT-indicator. Titrate with EDTA solution

till wine-red colour changes to clear blue. This marks the end point of the titration. Repeat the

titrations for constant titer values. Let volume EDTA solution used by V3 mL.

Preparation of primary Standard hard water solution:

Molarity (M) = Weight of CaCO3 X 1000

M. Wt of CaCO3 1000

Weight of CaCO3 = M X M. Wt of CaCO3

Dissolve ________ grams of pure, dry CaCO3 in minimum quantity of dil.HCl and then evaporate the

solution to dryness on a water bath. Dissolve the residue in distilled water to make 1 Liter solution.

Each mL of this solution thus contains 1mg of CaCO3 equalent hardness.

1 mL hard water solution = 1mg of CaCO3 equivalent hardness.

Standardization of EDTA using standard hard water

S.No Volume of StandardHard water (ml) Vs

Burette Reading Volume of EDTA solutionconsumed (V1)Initial Final

1 10 ml

2 10 ml

3 10 ml

Vs = 10 ml V1 =

V1=

V1= 10 ml (10 ml Standard hard-water reacting with 10 ml 0.01M EDTA solution)

Titration of Sample Hard water:

S.No Volume of Sample Hardwater (VH)

Burette Reading Volume of EDTA solutionconsume (V2)Initial Final

1 50 ml

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2 50 ml

3 50 ml

VH = 50 ml V2 =

V1=

V2 =Total hardness of water = 1000XV2

V1

Estimation of total hardness present in water sample:

Molarity of EDTA = M

Indicator – EBT

Colur change – Wine red to Pale blue

50 ml of water sample + 2 ml buffer solution + 1 drop EBT

S.No Volume of water

sample taken(ml)

Burette Reading Volume of EDTA solution consume

(V3)Initial Final

1 50 ml

2 50 ml

3 50 ml

VB = 50 ml V3 =

V1= 50 ml

V3 =

Permanent hardness = 1000XV3

V1

Temporary hardness = 1000 X [(V2-V3)] =

V1

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Result: The Temporary hardness of the given water sample _________ ppm.

The Permanent hardness of the given water sample _________ ppm.

The Total hardness of the given water sample _________ ppm.

Experiment-2

DETERMINATION OF PERCENTAGE OF COPPER IN BRASSMINERAL ANALYSIS (IODOMETRY)

Aim: To determinate the percentage of Copper present in the given Brass sample using a standard

solution of Potassium Dichromate and Hypo as the link solution.


Funnel, Burette,

Iodometric flask,Conical Flask,

20 ml Pipette & Simple balance with weights,

Chemicals Required: Brass sample,

Potassium Dichromate (K 2Cr 2O7),

Hypo (Na2S2O3),

Potassium Iodide (KI),6N Conc.HNO3,

NaHCO3,

6N Sulphuric Acid (H2SO4),Syrupy Phosphoric Acid (H3PO4),

Ammonia solution,

Potassiun thiocyanate (KSCN)

Starch & distilled water.

Principle: Brass in an alloy which consists mostly of copper (60 to 80 %) and zinc ( 20 to 40% ) along

with small amounts of lead ( 0 to 2% ) , tin ( 0 to 6% ) and iron ( 0 to 1% ).The experiment consists of dissolving a known quantity of brass in nitric acid, removing the

nitrate by fuming with sulfuric acid, adjusting the pH by ammonium hydroxide, complexion the iron

present using phosphoric acid, and finally titrating the copper ions with hypo by the iodo-metricmethod.

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When the brass sample is dissolved in nitric acid, the copper present is brought into solution inthe form of cupric ions. At the same time, tin is converted to meta-stannic acid

(SnO2.4H2O ), lead and zinc are oxidized to their respective soluble divalent ions, while iron is

converted to ferric ions. During the treatment with sulfuric acid, nitrate is eliminated, the meta-stannicacid is re-dissolved and lead ions are precipitated as PbSO4 while all other metals go into solution as

their respective sulfates. Out of all the metal ions present in solution, only Cu2+ and Fe3+ are reducible

by iodide. The interference by iron is eliminated by titrimetrically determined by the iodometric

method.Chemical reactions:

2Cu2+ + 4I- 2CuI + I2

2S2O3 + I2 S4O6- + 2I-

Cu = I = S2O3-

Procedure:

1. Preparation of standard potassium dichromate: Weigh out accurately about 0.490 gm or 490 mg of the given pure crystalline sample of potassium dichromate and transfer into 100

ml standard (volumetric) flask provided with a funnel. Dissolve the dichromate in a small

quantity of distilled water, and make upto the mark. The contents in the flask are shaken wellfor uniform concentration. Calculate the normality of potassium dichromate.

2. Standardization of sodium thiosulphate: Rinse the burette and fill it up with hyposolution without any air bubbles. Note the burette reading. Take about 20 ml of 10%KIsolution in a clean conical flask and add 2 grams of sodium bicarbonate followed by 5 ml of

concentrate HCl gently rotate the flask for mixing the liquids. Rinse the pipette with a little

of potassium dichromate solution and then transfer 20 ml of the same to the conical flask.

Shake it well, stopper it, and keep it in dark place for 5 minutes. Titrate the liberate iodine byrunning down hypo from the burette with constant stirring. When the solution attains a pale

yellow colour add 2 ml of freshly prepared starch solution. The colour changes to blue.

Continue the titration drop-wise till the colour changes from blue to light green indicating theend point. Repeat the titration for concurrent values.

3. Estimation of copper:

About 0.25 g or 250 mg of clean and dry brass sample is accurately weighed and transferredinto a conical flask. Add bout 10ml of 6 N HNO3 and the flask is gently heated until the brass

sample is completely dissolved. Then 10ml of conc. H2SO4 added and the solution is

evaporated on a sand bath to copious white fumes. The mixture is then allowed to cool and

20ml of water very carefully add from the sides of the flask, in instalments of 1ml at a timewhile cooling under a tap. Boil the solution for 2 minutes and cool. Add liquor ammonia

drop-wise while shaking the flask vigorously until the appearance of blue cupric ammonium

complex. Now, 6N H2SO4 is slowly added drop wise until the dark Blue colour disaapears.Then add 2 ml of syrupy phosphoric acid is added. The solution is cooled and transferred to a

100ml volumetric flask. The volume is made up to the 100ml mark using distilled water. 25

ml of this solution is pipette out into a 150ml conical flask and add about 1 g of solid (KI)

potassium iodide. The flask is shaken and the solution is immediately titrated with standardsodium thio-sulphate solution until the solution assumes a faint yellow colour of iodine.

About 3 ml of 1% starch solution are added and the titration is continued until the blue colour

begins to fade. At this stage, about 0.5g or 500 mg of potassium thiocyanate (KCNS) isadded and the titration is continued until the blue colour just disappears. The titration is

repeated twice with fresh 25ml portions of the solution to confirm the titer value.

4. Weight of Brass Sample (B):

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W1 = Weight of bottle + Brass sample = ____________ gmsW2 = Weight of bottle = ____________ gms

Weight of Brass Sample = B = (W1-W2) = ____________ gms.

Weight of the Brass Sample = B =

5. Preparation of Standard (K 2Cr2O7)solution:

W1 = Weight of bottle + substance = ____________ gms

W2 = Weight of bottle = ____________ gmsWeight of substance = (W1-W2) = ____________ gms.

Normality of the solution = (W1-W2) X 10__ = (W1-W2) X 10 =

Equivalent Weight 49

S.No Volume of standard

(K 2Cr 2O7)solution (V1)

Burette Reading Volume of

consume (V2)Initial Final

1 20 ml

2 20 ml

3 20 ml

V1 = V2 =

N1 = Normality of Potassium dichromate =V1 = volume of Potassium dichromate = 20 ml

N2 = Normality of Hypo =?

V2 = Volume of Hypo =

N1V1 = N2V2

N2 = N1V1 =

V2

N2 = Normality of Hypo =

S.No Volume of Copper solution (V3)

Burette Reading Volume of consume (V4)

Initial Final

1 20 ml

2 20 ml

3 20 mlV3 = 20 ml V4 =

N3= Normality of Copper solution = ?

V3 = volume of Copper Solution = 20 ml N4 = Normality of Hypo =

V4 = Volume of Hypo =

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N3V3 = N4V4

Normality of Copper solution = N3= N4V4

V3

The amount of copper present in the solution can be calculated on the basis that

1ml of 1N Na2S2O3 = 0.06354 g of Cu.

Amount of Copper present in the whole of the given solution (100 ml) = Z = N3 X 63.54

100

Weight of the Brass Sample = B =

Percentage of Cu in the brass sample : (% of Cu in brass) = Z X 100B

Result: Percentage of Copper present in the whole of the given Brass sample(100 ml) = ______ %

Experiment-3

ESTIMATION OF MANGANESE DIOXIDE IN PYROLUSITE.

MINERAL ANALYSISAim: To estimate the amount of MnO2 present in the given sample and hence percentage purity of

Pyrolusite.


Burette,Conical Flask,

20 ml Pipette,

Funnel,Simple balance with weights,

Heating equipment.

Chemicals Required: Pyrolusite,

4N Sulphuric acid (H2SO4),

0.1 N Di Sodium oxalate solution,1M Sulphuric acid (H2SO4),

Potassium permanganate (KMnO4),

Distilled water.

Principle: The MnO2 present in the pyrolusite sample is reduced by a known excess of standard

sodium oxalate in acid medium. The unreacted sodium oxalate is titrated against a standard KMnO4,until pale pink coloured end point is obtained.

MnO2 + H2SO4 + H2C2O4 2CO2 + 2H2O + MnSO4

1ml of 1N KMnO4 = 1 ml of 1N Na2C2O4 = 0.04346 gm of MnO2 = 0.01099 gm of Mn

1 ml of 1N KMnO4 = 1 ml of 1N As2O3 = 0.04346 gm of MnO2

Preparation of Standard Di-Sodium Oxalate solution: Weigh accurately 0.67 gm of Di-Sodium

Oxalate and transfer into 100 ml standard flask through a funnel. Dissolve the compounds small

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amount of distilled water and make up to the mark with distilled water. Shake the flask vigorously for uniform standard Di-Sodium Oxalate solution.

Standardization of KMnO4 solution:

Take 25 ml of the 0.1N sodium oxalate solution in a conical flask, add 150 ml of 1M H2SO4 solution.

Titrate with the KMnO4 solution at room temperature until the faint pink colour appears. Warm the

solution to 60 to 700 C and continue the titration to a faint permanent pink colour.

Estimation of MnO2: Weigh out accurately about 0.2 gm or 200 mg of the given powdered pyrolusite

sample into a clean dry conical flask and add 50 ml of standard sodium oxalate solution and add 50 ml

of 4N (H2SO4) sulphuric acid, put a small funnel into the mouth of the conical flask. Heat with smallflame till particles are MnO2 disappear in the conical flask. Rinse the funnel with distilled water into

the conical flask, titrate the hot solution, containing the unreacted sodium oxalate with standard

KMnO4 solution till there is a pale pink colour.

Result: Percentage purity of the given sample of Pyrolusite =

Preparation of Standard sodium oxalate solution:

W1 = Weight of bottle + substance = ____________ gms

W2 = Weight of bottle = ____________ gms

Weight of substance = (W1-W2) = ____________ gms.

Normality of the solution = (W1-W2) X 10 = __________X 10

Equivalent Weight 67

Standardization of KMnO4 solution:

S.No Volume of

standard disodium oxalate

solution (V1 )


KMnO4consume(V2)Initial Final

1 25 ml

2 25 ml

3 25 ml

V1= V2 =

N1 = Normality of di sodium oxalate =

V1 = volume of di sodium oxalate = 25 ml

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N2 = Normality of KMnO4 =?

V2 = Volume of KMnO4 =

N1V1 = N2V2

N2 = N1V1 =

V2

N2 = Normality of KMnO4 =

Weight Of the Pyrolusite Sample:

W1 = Weight of bottle + Pyrolusite = ____________ gms


Weight of Pyrolusite = (W1-W2) = ____________ gms.

S.No Volume of

standardsolution


consume (V)Initial Final

1 50 ml

2 50 ml

3 50 ml

V =

Calculations:

Weight of the Ore taken =

Volume of 0.1N Di sodium oxalate solution added in the experiment = 50 ml

Volume of 0.1N KMnO4 run down = V =

Volume of 0.1N KMnO4 consumed = (50 – V) =

1 ml of 1N KMnO4 = 1N Na2C2O2 = 0.04346 g of MnO2

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Percentage of MnO2 = (50 - V) X Normality of KMnO4 X 0.04346 X 100

Weight of the sample

Result: Percentage purity of the given sample of Pyrolusite =

Experiment-4

DETERMINATION OF FERROUS IRON IN CEMENT BY COLORIMETRIC METHOD

(Colorimetric Estimation)

Aim: To estimate the amount of Iron (Ferric) present in a sample of cement by calorimetrically usingammonium thiocyanate as a reagent.

Apparatus: 250 ml beaker,

Glass rod,

Watch glass,100 ml standard flask,

Burette,

10 ml Pipette,Simple balance with weights

Colori-meter,

Heating-equipment.

Chemicals Required: Cement sample,

Conc. Nitric acid (HNO3),

Hydrochloric acid (HCl)Ammonium thio-cyanate &

Distilled-water.

Principle: Ammonium thio-cyanate yields a blood red colour with ferric iron and the colour produced

is stable in nitric acid medium. Its optical density is measured in a photo colorimeter and the

concentration of ferric iron is found from a standard calibration curve.

Procedure:

1. Dissolution of the sample: Weight out accurately about 0.1 gram of the cement sample into aclean 250 ml beaker add about 5 ml of water to moisten the sample. Place a glass rod and cover

the beaker with a watch glass add about 5 ml conc. Hydrochloric acid (HCl) drop-wise and

heat the solution till the sample dissolved. Keep the beaker on a small flame and evaporate thesolution to almost dryness to expel the excess acid.

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Take the beaker out of the flame and add about 20 ml distilled H2O to dissolve the contents.Transfer the solution into 100 ml standard flask. Wash the beaker twice with small portions of

distilled water, and add the washings to the standard flask. Make up the solution to 100 ml with

distilled water. Shake the flask well uniform concentration.

2. Development of Colour: pipette out 10 ml of the solution prepared above, into a 100 ml

standard flask, add 1 ml of conc. Nitric acid (HNO3) and 5 ml of 40% ammonium thiocyanate.

Make up the solution to 100 ml with distilled water and shake the flask well for uniformconcentration. Find out the optical density of the solution using the photo colorimeter and the

concentration of the ferric iron from the calibration curve.

Result: Percentage of Ferric iron present in the cement sample =

Weight of the sample:

W1 = Weight of bottle + sample = ____________ gms


Weight of sample = (W1-W2) = ____________ gms.

Standard value for calibration curve

Concentration in Milligrams O. D

0.05 0.11

0.10 0.22

0.15 0.32

0.20 0.40

0.25 0.50

0.30 0.62

0.35 0.70

0.40 0.80

X = corresponding amount of from the calibration curve =

Calculation:

Percentage of Fe3+ present in the given cement sample = X x 10 x 100

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(W1 – W2) mg

Result: Percentage of Ferric iron present in the cement sample =

Experiment-5

CONDUCTOMETRIC TITRATION OF STRONG ACID Vs STRONG BASE

(CONDUCTOMETRY)

Aim: To estimate the amount of HCl present in given solution.

Apparatus: Conductivity meter, Conductivity cell, Burette, Pipettes, Beakers, stirrer.

Chemicals Required: Pure sample of Oxalic acid, 0.02M HCl and 0.1M NaOH.

Theory: Electrolytic conductivity is a measure of the ability of a solution to carry electric current.Solutions of electrolytes conduct electric current by the migration of ions under the influence of

applied field. Like metallic conductors they obey ohms law. At a given temperature the conductivity

depends upon the concentration of the electrolyte.

Conductivity cell: The electrolytic conductance of an electrolyte is measured in conductivity cells,

which are specially designed. These are available in various sizes and shapes consisting of 2electrodes. Each electrode is a pH disc or plate coated with finely divided Pt black. The electrode iswelded to a Pt wire which is fused to a glass tube. The glass tubes are firmly fixed in the cell so that

the distance between the electrodes would not change during the experiment. The cell is open at one

end; the electrolyte whose conductivity is to be measured is dissolved in water and is taken in a beaker. The conductivity cell is placed in the solution and is connected to the conductometer.

Cell constant X: X of a conductivity cell is the ratio of distance between the 2 electrodes and theexposed area of one of the electrodes.

X = 1

a

Specific conductance: It is the conductance of ions present in one cubic centimeter of the solution. If the cell constant of a conductivity cell is 1.0 the measured conductivity of an electrolyte is its specific

conductivity. The cell constant of a conductivity cell is seldom 1.0 cm-1, also measuring ‘l ‘and ‘a ‘are

troublesome. Hence the given cell is calibrated for its cell constant, with the help of an electrolyticsolution normally, a standard KCl whose specific conductivity is known.

Cell constant = known specific conductance / measured conductance

Principle: The electrical conductance of an electrolytic solution is proportional to a) the ionic

concentration i.e. number of ions present in the solution and b) the ionic mobilies. The ionic motilities

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in aqueous solutions are generally of the order of 6.0 x 10 -4 cm2, sec-1 volt-1. But the ionic mobilities ofH+ and OH- are abnormally high, H+ = 36.3 x 10-4 and OH- = 20.5 x 10-4 cm2 sec-1 volt-1. Thus the

conductance of an electrolyte is quite sensitive to concentration of H+ and OH- ions.

Titration of strong acid HCl with strong base NaOH: In solution HCl is completely ionized. The

mobility of H+ ions is high; hence the conductance of HCl solution will also be high. As NaOH is

added to HCl, the fast moving H+ ions are removed by OH- ions of the base as water.

H3O+ + OH- = 2H2OIn solution water is little ionised and Na+ added are slow moving compared to H+ ions of acid. Hence

as the titration proceeds, the conductance of titrand HCl decreases gradually till the equivalent point is

reached. At the equivalence point the conductance of the solution will be the minimum addition of the base beyond end point adds Na+ and fast moving OH- ions, resulting in a gradual increase in

conductance.

Standardization of NaOH solution: Pipette out 20 ml of prepared NaOH solution in a conical flask.Add 1-2 drops of methyl orange indicator and titrate against standard oxalic acid solution.

Determination of Cell constant: Take a conductivity cell and determine its cell constant using a 0.1

N KCl solution.

Conduct metric titration: The burette is rinsed and filled with 0.1 M NaOH, 40 ml of given acid is

placed in a 100 ml beaker. The cell is washed with conductivity water which is placed in HCl solutionand see that the electrodes of cell are completely immersed in the solution. The cell is fixed in a cell

holder and is connected to the conductivity bridge. The conductance of HCl solution is noted at a timewhen 1 ml of NaOH from the burette is added into HCl solution. After each addition the solution is

stirred gently with a glass rod and the conductance of HCl is noted. The titration is continued till 20 to

25 ml of NaOH is added.

Graph: Plot a graph between the conductances measured on Y-Axis and volume of alkali added (X-

Axis) we get a V shaped graph the point of intersecting will be the End-Point of titration and willdetermines the volume of alkali required for neutralization of the acid.

Preparation of Standard Oxalic acid solution:W1 = Weight of bottle + substance = ____________ gmsW2 = Weight of bottle = ____________ gms

Weight of substance = (W1-W2) = ____________ gms.

Normality of the solution = (W1-W2) X 10 = __________X 10

Equivalent Weight 63.03

Standardization of NaOH solution:

S.No Volume of standard oxalic

acid solution(V1 )

Burette Reading Volume of NaOHconsume (V2)

Initial Final

1 25 ml

2 25 ml

3 25 ml

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V1= V2 =

N1 = Normality of Oxalic acid =

V1 = volume of Oxalic acid = 25 ml N2 = Normality of NaOH =?

V2 = Volume of NaOH =

N1V1 = N2V2

N2 = N1V1 =

V2

N2 = Normality of NaOH =

S.No Volume of NaOH solution added (ml) Conductivity of the solution (ohm-1)

1 0.0

2 1.0

3 2.04 3.0

5 4.0

6 5.0

7 6.0

8 7.0

9 8.0

10 9.0

11 10.0

12 11.0

13 12.0

14 13.0

15 14.016 15.0

17 16.0

18 17.0

19 18.0

20 19.0

21 20.0

22 21.0

23 22.0

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Engineering Chemistry Lab Manual (I B.Tech Common to All)24 23.0

25 24.0

26 25.0

Volume of the Hydrochloric acid (HCl) used = 40 ml

Volume of NaOH required to reach Equivalent Point = V =

Normality of NaOH =

Strength of HCl = End point titer valve (V) X Normality of NaOH =

Volume of HCl used

Result: The strength of HCl calculated is __________ N.

Experiment-6

TITRATION OF STRONG ACID VS STRONG BASE BY POTENTIOMETRY(POTENTIOMETRY)

Aim: To estimate the amount of HCl present in given solution.

Apparatus: Saturated calomel electrode,Platinum electrode,Quinhydrone electrode,

Potentiometer,

Salt bridge,Burette,

Pipette,

Beakers & glass rod etc.

Chemicals Required: Pure sample of Oxalic acid,

0.1M HCl and 0.1M NaOH.

Principle: Quinhydrone (Q) is an equi-molar mixture of quinine C6H4O2 and Hydroquinone

C6H4(OH)2. In acidic medium the following redox equilibrium is established.

Q +2H+ + 2e- -- QH2

A pinch of quinhydrone added to an acid solution and a Pt wire or foil dipped in it constitutes a half

cell such electrodes are called indicator electrodes. This is coupled with a reference electrode through

a salt bridge making it an electrochemical cell.Ex: (-)saturated calomel electrode / salt bridge / Qunihydrone + Acid solution / Pt +

(or) (-) Pt, Hg / Hg2Cl2 (s) / KCl (saturated) // H+ , QH2, Q/Pt (+)

CELL REACTION:

2 Hg(s) + Q + 2Cl-(aq)- Hg2Cl2(s) + QH2

Ecell = Eright – Eleft in terms of reduction potentials

Ecell = EQE – 0.242 ---------(1)The left hand half cell is fixed i.e., its potential is constant. Now the right hand half cells potential

depends on H+ activity. The fundamental equation governing the effect of activity of the ions on the

voltage of an electrode or a cell is Nernst equation given byEcell = Ecell - (RT / nF ) lnk

Where k is equilibrium constant of a general reaction aA + bB - cC + dD

The potential will be EQE + nE0QE – (RT /2F ) ln (QH2) / (Q) (H+)2

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EQE = E0QE + 0.0591 log (H+) – 0.242Ecell = 0.458 – 0.0591 pH

During the titration, against and alkali, H+ ion concentration in the half cell containing QH2 wildecrease correspondingly the Ecell decreases. The emf will change slowly in the beginning how ever

at the end point relatively higher potential difference will be obtained and then again it will change

slowly. After the end point 5 or 6ml more of the bas is added, quickly and EMF is recorded. Repetition

of titration is done by adding 0.2ml of Na OH at a time near the end point. A graph is plotted betweenEMF and volume of base added. The point of inflection where the graph changes its direction is the

end point. A differential plot of (∆ E/∆ V) against V* give s a curve whose peak indicates equivalent point.

PROCEDURE:

1) Calibrate the instrument before starting the experiment.

2) Take 20 ml of acid solution in a 100 ml beaker and immerse the pH electrode in to the solution

3) Firist carry out the rough titrations by adding 1 ml of NaOH and measure the EMF at eachstage.

4) After finding the range of end point, then take fresh sample of acid solutions in a beaker andcarry our the titrations repeatedly by adding 5 ml, 3ml, 2ml, 0.5ml, 0.2ml and 0.1mlsuccessively.

5) After the end point, the volume of alkaline added is increased to 1 or 2 ml. Near the end point

smaller addition should be added by micro burette.6) Plot pH values or EMF values against the volume of NaOH added. Draw a smooth curve, the

point of intersection gives the equivalence point.

7) Plot another graph between ∆ E /∆ V values against the titre readings abscissa. The maximum

of the curve represents the equivalence point.

Graph: Plot a graph between cell EMF on Y-Axis and Volume of NaOH on X-Axis. For getting the

exact neutralization point another graph drawn ∆ E/∆ V Vs Volume of NaOH from this graph thevolume required for neutralization is known.

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TABLER FORM:

S.No Volume of NaOH(ml)

EMF value (mv) ∆ E ∆ V ∆ E/∆ V

1 0

2 1

3 2

4 3

5 4

6 5

7 6

8 7

9 8

10 911 10

12 11

13 12

14 13

15 14

16 15

17 16

18 17

19 18

20 19

21 2022 21

23 22

24 23

25 24

26 25

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Volume of NaOH (Eqv.point) =

Normality of NaOH =

Volume of HCl taken =

Normality of HCl = volume of NaOH (Eqv.point) X Normality of NaOHVolume of HCl taken

RESULT: the normality of HCl by titrating with NaOH using potentiometer is ________ N .

Experiment-7

DETERMINATION OF VISCOSITY OF SAMPLE OIL BY REDWOOD VISCOMETER .OBJECTIVE:-

1. To determine the Absolute and Kinematic Viscosities of a given sample of oil at varioustemperatures starting from room temperature.

2. To draw the following graphs.

Absolute viscosity Vs Temperature.

Kinematics Viscosity Vs Temperature.

APPARATUS:-

Red wood Viscometer-I,

Thermometers 2No. (0--1100),

Stop watch,

Measuring flask (50ml),

Energy regulator and sample oil.

THEORY:-

Viscosity is one of the important properties of a lubricant, which helps in selection of oils for their suitability for lubricating purposes. A lubricant when used is aimed at reducing friction between different moving parts of a machine by avoiding direct metal-to-metal contact. The thin film

of oil, formed between the moving surfaces, keeps them apart and thus the frictional resistance is

entirely on account of the shearing of the liquid. The viscosity of the fluid measures the amount of the

internal friction.

The objective of this experiment is determining the viscosities, therefore, is to ascertain

whether the oil is sufficiently viscous, under the high pressure and temperature conditions of the

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machine, to adhere to the bearing. The variation of viscosity with temperature is of great importance tothe engineer in all problems of fluid flow and fluid friction and also in pumps, fans and all types of

bearings.

Absolute Viscosity:-

It is the shear force required to move a layer of the oil of one-centimeter thickness over an area of one square centimeter thickness. In C.G.S system it is expressed in poise and in SI system it

is expressed in 1N-Sec/m2

1N-Sec/m2 = 10 poise; dyne-sec/cm2=poise

Kinematic Viscosity:-

The ratio of Absolute Viscosity to the density is called Kinematic Viscosity. In C.G.S

system it is expressed in Stokes and in SI system it is expressed in m2/sec

1m2/sec = 104 stokes; stoke = cm2/sec

Effect of temperature on Viscosity:

Increase in temperature causes a decrease in the viscosity of a liquid; where as viscosity

of gases increase with temperature the viscous forces in a fluid are the outcome of inter molecular

cohesion and molecular momentum transfer. In liquids the molecules are comparatively more closely packed, molecular activity is rather small and so the viscosity is primarily due to molecular cohesion.

Since the rate, at which a fluid will flow through an aperture, increase as the internal friction of

the fluid decreases, the rate of flow through an orifice or short tube may be used as a means for measuring viscosity. This is the principal involved in Redwood Viscometer-I, which is used in United

Kingdom for measuring viscosity. The time in seconds required for 50ml of oil to gravitate through the

Redwood Viscometer at a given temperature is expressed as its viscosity in Redwood seconds at that

temperature. The Kinematic and Absolute viscosities can be determined from Redwood seconds byusing the following formulae

Kinematic Viscosity (υ) = At – B/t

Absolute Viscosity (µ) = υ.ρ

Where A and B are constants, t is Redwood seconds and ρ is the density of the fluid.

Redwood Viscometer-I is used for determining the viscosity for low viscosity oils. It has anorifice of diameter 1.62 mm with a length of jet of 10mm. The values of A and B for Redwood

Viscometer-I are as follows

Viscosity range in R.Iseconds

A B

40-85 0. 264 190

85 to 2000 0. 247 65

DESCRIPTION OF APPARATUS:

The Redwood Viscometer consists of a heavily silver plated oil cup with a dishshaped bottom with a standard hole in hemispherical seating. A spherical ball valve is placed to close

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the orifice. The oil cup is surrounded by a bright chrome plated water bath. The water bath is mountedon a stand with leveling screws. The level to which the oil is to be filled into the cup is given by an

index fixed to the inside wall of the oil cup. A standard size stainless steel jet is fitted at the center of

the bottom of the cup for the flow of oil to be measured. The cylindrical water bath is provided with atap for emptying. The water bath surrounding the oil cup provided with three vanes, having their upper

and lower positions rotated in opposite directions to facilitate stirring, which is carried out manually.

For ascertaining the level of equipment a flat circular spirit level is used. The

flow of oil is regulated by the ball value.The oil cup cover is fitted with an insulated handle, and has suitable

arrangement to facilitate thermometer and value rod. The circular spirit level is mounted on a plate to

fit on the upper end of the oil cup.

PROCEDURE:-

i. Clean the oil cup and dry it. Examine the jet and ensure that it is clean and not obstructed.

ii. Mount the bath on the stand and level it with the help of spirit level and leveling screws.

iii. Fill the water bath with water until the heating element is below the water surface. Fill the oil

cup with oil up to the mark.

iv. Fix the thermometers in the provided space intended for measuring water and oil temperatures.

v. Press the connector to the water bath heater pin and the three-pin plug to the plugged to the

socket of the energy regulator box. The three-pin plug from the energy regulator is connectedto the socket of the main supply. Keep the energy regulator knob at the eighty marks and

switch ON the main supply.

vi. Water gets heated and the water temperature reaches 600C stir them well and ensure that the

water and oil temperature are nearly equal.

vii. Place the clear dry 50ml receiving flask centrally below the jet with the top of the neck a few

mm from the bottom of the jet. Open the orifice by lifting the ball valve and note the timetaken for the collection of 50ml oil with the help of stop watch. Note down the time taken is

seconds for the oil to get filled in the flask up to the red mark also note down the water and oiltemperature repeat the procedure for various temperatures using the same oil and tabulate the

readings.

OBSERVATIONS:-

Type of oil used:

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Calculation of Density:

S.NO Weight of the empty jar W1 g

Weight of the jar with fluid

W2 g

Volume of the jar in cc

Net weight of fluid

W= W2- W1 g

Density ρ =W/V g/cc

1

2

3

4

5

S.No Temperature in 0C Density of oil(g/cc)

Time takenin Sec.

KineticViscosity in

Stokes

AbsoluteViscosity in

poiseWater Oil

1

2

3

4

5

SAMPLE CALCULATIONS:-

The values obtained are

Temperature of the oil =

Density (ρ ) of the oil =

Time for filling the 50ml of the oil =

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Then Kinematic Viscosity (υ) = At – B/t centistokes

Where A & B are viscometer contains

A = 0.26, B= 171.5, t = time in seconds for collection of 50 ml of oil in the flask

The Absolute Viscosity = kinematic viscosity X Density = υ X in centipoises

Experiment-8

DETERMINATION OF SURFACE TENSIONAim: To determine the effect if soap and detergent on the surface tension of water using aStalagmometer

Apparatus: 1. Stalagmometer 2. Volumetric flask 3. Small rubber tubing 4. Screw type pinch cock

Chemicals: 1. Detergent solution 2. Soap solution

Principle: The size of the drop falling off from the end of tube depends on the surface tension of theliquid and the size of the capillary end, which provides the line of attachment for the drop. Thus when

a liquid is allowed to flow through a capillaty tube, a drop will increase in size to a certain point and

then fall off. The total surface tension supporting the drop is 2r ϒ where r is the radius of the outer

circumference of the dropping end of the capillary tube. It is along this line that liquid, glass and air

meet and the force acting along the circumference, hence W = 2r ϒ , where W is the weight of the

drop and 2π r is the circumference of the external wall of the capillary tube. The surface tension of the

liquid can therefore be determined from the weight of a single drop and the external radius of the

dropping tube.If we have two liquids such that

W1 = 2π r ϒ 1 and W2 = 2π r ϒ 2 then W1/W2 = ϒ 1/ ϒ 2

Thus the drop weight method can be employed for comparing the surface tension of two differentliquids. However, it is easier to count the number of drops formed by equal volumes to two liquidsthan finding the weight of a single drop. For two different liquids, the weights of equal volumes are

proportional to their densities. Let N1 and N2 be the number of drops of liquid produced from the same

volume V of the two liquids.Volume of a single drop = V / N1

Weight of a single drop = (V / N1) d1 or 2π r ϒ 1 = (V / N1) d1

Similarly for liquid 2

2 π r ϒ 2 = (V / N2) d2

Where d1 and d2 are the densities of the respective liquids. Dividing these two equations we get

ϒ 1 / ϒ 2 = (N2.d1) / (N1.d2)

Procedure:

• Take a clean and dry Stalagmometer

• Attach rubber tubing with a screw pinch cock to the upper end of the stalagmometer to control

the flow of the liquid and clamp it to a stand.

• Make marks above and below the bulb with a marker pen if it is not marked.

• With the help of the rubber tubing, suck distilled water into the stalagmometer till the level

rises above the upper mark.

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• Now allow the liquid to flow through the capillary (control the flow rate using the crew pinch

cock) and count the number of drops formed (N1) till the liquid level reaches the mark below

the bulb.

• Dilute the given stock soap solution ( 1%) to appropriate dilutions as given below using a burette and determine the number or drops for each of these concentrations. Tabulate the data.

• Repeat the above procedure for 0.5, 0.1 and 0.05 % of detergent solution also and tabulate it as

above.

SNo Volume of water

+ Volume of

soap/detergent

solution (ml)

Concentration

of

soap/detergent

solution

Exp.1 Exp.2 Average

(N)

Surface

tension

(dynes/cm)

1 50 + 0 Pure water

2 25 + 25 0.5 %

3 45 + 5 0.1 %

4 47.5 + 2.5 0.05 %

Calculations: Surface tension of water at 25°C = 72 dynes / cm

r 1 = Surface tension of the reference liquid (i.e., water)

r 2 = Surface tension of the test liquid

r 1 = N2.d1

r 2 N1.d2

Result : The surface tension of the given liquid = ……….dynes / cm

Precautions:

• Number of drops per minute must be in between 15-20

• The lower end of stalagmometer should be free from grease hence wash the stalagmometer first with

benzene or NaOH and then with chromic acid.• Stalagmometer should be kept in a vertical position.

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Experiment-9IDENTIFICATION OF FUNCTIONAL GROUPS PRESENT IN ORGANIC COMPOUNDS

S.No Experiment Observation Inference

I PRIMARY TESTS:

a) State Solid / Liquid

b)Colour Colourless

liquid

Aldehydes, ketones etc.,

Yellow

coloured liquid

Nitro compound

Colourless

solid

Acids, amides, anilides, carbohydrates, etc.,

Brown (or)dark coloured

solid (or)

liquid

Phenols, aromatic amines etc.,

c)Odour Pleasant Nitro compounds

Phenolic Phenols

Aniline likesmell

Aromatic amines

Oil of bitter

almond

Nitrobenzene, benzaldhyde

II IGNITION

TEST

Smoky Aromatic compound

Non-luminous Aliphatic compounds containing low percentage of

carbon

Charring Compounds such as carbohydrate & its salts get

charred on ignition.

III SOLUBILITY:

Solubility test: One drop of the liquid or small quantity of the solid is dissolved in the

following:

Experiment Observation Inference

a)Ether Insoluble May becarbohydrate/amide/imide/anilide

b)Water Soluble, solution is neutralto litmus

May be carbohydrate

Solution turns blue litmusred

May be acidic compound

c)Saturated

NaHCO3

solution

Soluble with effervescence

and regenerated onacidification with dil.HCl

May be Carboxylic acid

Slow effervescence Polyhydric Phenols

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Slow effervescence &

solution turns Yellow

Nitro phenols

d)Dilute NaOH

solution

(changes in thecold are

observed &

heated if necessary)

No characteristic change Presence of ketones, amines, aromatic

nitro compounds

Dissolves readily in the

cold & substance is

regenerated on adding

conc. HCl

Aromatic acids, phenols may be present

Dissolves & solution turns

Yellow colour is removedon adding HCl

Nitro phenols, phenolic aldehydes may

be present

Dissolves readily forminga Yellow or brown

solution on boiling

Carbohydrates may be present

Dissolves in cold &

solution turns Yellow,

Brown & finally dark on

shaking

Polyhydric phenols may be present

Ammonia gas is evolvedon boiling

Amides may be present

Oily drops are formed with

aniline like odour on boiling

Anilides or Toluidines may be present

e) Dil. Na2CO3 Soluble with effervescence May be carboxylic acid

Soluble without

effervescence

May be Phenolic Group

f) Dil. HCl Soluble and regenerates on

adding alkali

May be basic compounds like amines

g) Action of Conc.

H2SO4: To a small

quantity of organiccompound in a dry

test tube add conc.

H2SO4 and note the

change in the codeand then warm

gently.

Blackening with

effervescence with the

evolution of CO and(or) CO2 & SO2

Carbohydrates or certain hydroxyl

aliphatic acids like Tartaric acid.

Blackening withouteffervescence

Polyhydric Phenols like Resorcinol

CO and CO2 evolved,

no Blackening

Oxalates (or) Oxalic acid

IV Test for Un-saturation


a) Action of bromine inCCl4: to 1ml of brominein CCl4, add drop of the

liquid or small quantity

of the solid.

De-colorisation of brominewithout evolution of HBr.

Un-saturation is present.

No de-colourisation Saturated compound

b)Baeyer’s Test:

Action of dil. KMnO4:

Add one drop of the

Decolourisation of KMnO4

with Brown ppt.

Unsaturated compound

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liquid or small amount of

the solid to 1 ml of dil

KMnO4

No decolourisation of

KMnO4

Saturated compound

c) Br water: 1 ml of

Bromine water add adrop of Liquid or small

quantity of solid.

Decolurisation Unsaturated compound

No Decolurisation Saturated compound

S.No Ether H2O NaHCO3 NaOH HCl H2SO4 Compound1 + - + + - + Carboxylic acid

2 + - - - + + Base

3 + - - - - - Hydrocarbon

4 - + + + + + Carbohydrate

5 + - - - - + Neutral Compound

FUNCTIONAL GROUP ANALYSIS

A simple organic compound has one functional group but it may contain two or more functionalgroups. All these commonly found functional groups have been divided into four groups. The groups

correspond to various elements in the organic compounds and are given below.

Type Elements present in

compound organic

Organic compound and its functional group

1. a)C&H

b) C,H& O

Hydrocarbons

Carboxylic acid, phenol and alcohol(-OH),aldehyde,ketone, ether and ester

2. a)C,H&N b)C,H,N& O

AminesAmides, nitro compounds & anilides

3. a)Halogens C,H,& X

b) Halogens and C,O,AX,O

Halogenated hydrocarbons

Acid halides,chloral hydrate.4. C,H,S,O Sulphonic acid

ELEMENTAL ANALYSIS

C,H and O are considered as basic elements of organic compounds. Other than these threeelements, the elements that are most commonly present in organic compounds are nitrogen, sulphur

and halogens. The presence of these elements is detected by Lassaigne”s test.

Preparation of sodium fusion extract:

Heating procedure for liquids: Gently heat a small piece of freshly cut and dried sodium in an

ignition tube in the beginning and then to red hot. Remove the red hot ignition tube from the flame and

add one drop of the liquid. Repeat the heating process again until the tube becomes red hot, remove

and add another drop of the liquid. Repeat the operation two or three times.Heating procedure for solids:

Gently heat a small piece of freshly cut and dried sodium in an ignition tube in the beginning

and then to red hot. Remove the red hot ignition tube from the flame and add a few milligrams of solid. Repeat the heating process again until the tube becomes red hot. In the case of solids there is no

need to add the compound again.

Take 3 to 4 ml of distilled water in a mortar and immerse the red hot ignition tube into water.Grind the ignition tube to pieces with the pestle, filter. Divide the filtrate into three parts and perform

the following experiments.

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Compounds containing:

C,H,N,O,S, Halogen (X) + Na NaCN + NaOH + Na2S = NaX


Lassaigne”s Test:Test for Nitrogen: To one portion of sodium

fusion extract add 2 drops of freshly prepared FeSO4 solution.Boil, cool and acidify with dil.H2SO4 with shaking until the

solution is clear. Now add few drops of FeCl3

Bluish / Green

Precipitate / colour Prussian blue colour

No colour change

Nitrogen

present Nitrogen

absent

1) TESTS FOR CARBOXYLIC GROUP (-COOH):

S.NO EXPERIMENT OBSERVATION INFERENCE

1. Add 1 ml of saturated sodium bicarbonate solution to 1 drop of the

liquid or small amount of the solid

CO2 gas evolved Carboxylic acid may be present.

No CO2 is evolved Carboxylic acidabsent.

2. Dissolve one drop of liquid or small

amount of solid in 1 ml aqueous alcoholand moisten the blue litmus paper

Blue litmus changes

to red.

Carboxylic acid may

be present.

No colour change. Carboxylic acid absent

3. Esterfication: Dissolve one drop of

liquid or small amount of solid in 5 ml

of methyl/ethyl alcohol and add 2-3drops of conc. H2SO4 and warm on

water bath and pour the content into

NaHCO3/Na2CO3 sol.

Fruity odour Carboxylic acid

presence is conformed

4. Phenolphthalein Test: Dissolve 0.2

gms of of the compound in water /

alcohol. add a drop of phenolphthalein

and well diluted NaOH sol. drop wise

Pink colour is

obtained

Carboxylic acid

presence is conformed

2) TETS FOR AMINES (-NH2):


1. Carbylamine test: add few drops of

chloroform to about 0.2 gms of thecompound and add 2-3 ml of ethanolic

sodium hydroxide / KOH mix well and

warm gently.

A foul smell of isocyanide is

observed, by adding conc.HCl smell can be destroyed.

Amine may be

present

2. Nitrous acid test: take 0.2 gms of the

given compound is 2 ml of dil. HCl andcool. Now add 10% aqueous NaNO2

sol.

A brisk effervescence is

appeared.

Amine

presence isconformed.

3. Diazotization test: dissolve 0.2 gms of the organic compound in 2-3 ml dil HCl

cool under tape water now add 2 ml of

2.5 % NaNO2 solution, cool again andadd .5 ml of alkaline beta napthol sol.

An orange red or a red dye isappeared.

Amine presence is

conformed.

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3) TEST FOR HYDROCARBONS(C&H):S.NO EXPERIMENT OBSERVATION INFERENCE

1. Sublimation test: to a few 0.2 gms of

the compound of 2 ml of the liquid

add 3ml of chloroform and shakewell. Then transfer a pinch of AlCl3

into a dry test tube and sublime then

add chloroform solution to thesublimed AlCl3 such that the

chloroform layer touches the AlCl3.

Red colour is appeared Mono cyclic

hydrocarbon is

conformed.

Blue or violet colour is

appeared.

Bicyclic hydrocarbon

is conformed.

Green colour is appeared. Poly hydrocarbon is

conformed.

4) TEST FOR CARBOHYDRATES:


1. Blackening with H2SO4: heat 0.2 gms

of the compound with 1ml of conc.H2SO4 .

Immediately charring and

blackening of thesolution is observed.

Carbohydrate

may be present

2. 2, 4 DNP test: To 0.5 gms of

compound in 1 ml of water add 1 ml of 2, 4 DNP reagents.

Orange ppt. separates. Carbohydrate

may be present

3. Molisch test: dissolve 0.2 gms of compound in 4 ml of water and add 3-4

drops of alcoholic Beta- napthol andadd 2 ml of conc. H2SO4 carefully fromthe sides of the test tube.

A deep violet coloured isformed at the junction of

two layers.

Carbohydrate isconformed.

5) TEST FOR CARBONYL COMPOUNDS:S.NO EXPERIMENT OBSERVATION INFERENCE

1. 2,4-DNP test:

To 2-3 drops of compound add 1 ml of the

2, 4-DNP reagent. Keep it in hot water bath

for few minutes.

An orange ppt of 2, 4-Dinitro phenyl

hydrazone is formed.

Carbonylcompound is

present

2. Schiff’s test:

To 1 ml of the compound add 5 ml of the

schiffs reagent and heat the mixture on awater bath for 2 minutes.

No purple colour is

developed

Aldehyde group

is absent

3. Tollen’s test:

To 1 ml of the compound add 5 ml of the

tollens reagent and heat the mixture on a

water bath for 5 minutes.

No silver mirror is

deposited or no grey

colour

Aldehyde group

is absent.

4. Fehlings test:

To 1 ml of the compound add 1 ml of

No red colour ppt is

formed.

Aldehyde group

is absent.

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Na2CO3 solution and 1 ml of the Fehlings

solution A and 1 ml of Fehling solution B.

Boil the mixture for 2-3 minutes.

5. Bisulphate test:

To 1 ml of the compound add 1 ml of saturated Sodium bisulphate solution.

White NaHSO3 product

is formed.

Ketone is

present.

Experiment-10

PREPARATION OF ACETYL SALICYLIC ACID (ASPIRIN)

Aim : Preparation of Acetyl Salicylic Acid (Aspirin) with using salicylic acid.

Apparatus: 250 ml Round bottom Flask,200 ml beaker,

Glass rod,

Funnel,Dropper,

Filter papers,Simple balance with weights

Chemicals Required: Salicylic acid,

Acetic AnhydrideAcetic acid

Conc. Sulphuric Acid (H2SO4) &

Distilled-water.

Chemical Reaction:

Procedure:

5 gms Salicylic acid and 10 ml Acetic anhydride taken in 200 ml Round Bottom Flask, mixwell, and add 1 or 2 ml Concentrated sulphuric acid . Heat it 50-600C on water bath for 15 minutes.

Cool and add 100 ml water and filter the precipitate. Recrystallize it with equal volume of alcohol and

water.

Result:

Yield =

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Melting Point =

Experiment-11DETERMINE THE RATE CONSTANT OF HYDROLYSIS OF METHYL

ACETATE

Aim: To determine the order of reaction and rate constant for the acid catalyzed hydrolysis of methyl

acetate.

chemicals: Methyl acetate,

0.5N HCL,

0.1NSodiumhydroxide, phenolphthalein indicator, ice.

Apparatus: Iodination flask 250ml,Burette,

pippete10ml,

250 ml conical flask.

Principle:

Hydrolysis of methyl acetate is catalysed by HCl. The rate of reaction is followed by titrating the

acetic acid formation during hydrolysis by sodium hydroxide at certain intervals of time.

Procedure:

• Fill the burette with 0.1N sodium hydroxide solution and fix to the stand. Take 90ml of 1NHClinto an iodination flask and add 10ml of methyl acetate.

• Mix thoroughly for 5 to 10 seconds and note time.

• Immediately pipette out 10ml of the reaction mixture into a clean conical flask containing iceand phenolphthalein indicator. Titrate it against 0.1N sodium hydroxide.

• Note the volume of sodium hydroxide required for titration as Vo pour the contents out, clean

the conical flask and keep it ready for next titration by adding cold water and indicator.

• After 10 mins of time pipette out another 10ml of the reaction mixture into the conical flask

and titrate against sodium hydroxide as before.

• Note the volume as V10.

• repeat the titrations at every 10mins of intervals upto 60 mins as V20,V30,V40 ,V50 and V60.heatthe reaction mixture on a water bath at 600c for 30 minutes cool and pipette out 10ml of

reaction mixture into a conical flask, add phenolphthalein indicator and titrate with sodium

hydroxide and note the volume as Vα

Result: the hydrolysis of acetic acid is a pseudo first order reaction the experimental value of K =

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From the value of the reaction rate constant at two temperatures calcilate the energy of

activation for the reaction using the equation:

Log K 2 = -- E [ 1/T2 – 1/T1]K 1 2.303R

E = T1 T2 X 4.567 X Log K 2T2 - T1 K 1

__________________________________________________________________________________

SV Group of Institutions

S.NO TIME Vol of NaOH Vα -Vt Log Vα -V0

____Vα -Vt

K1 = 2.303/t Log Vα -V0

_______________Vα -VtIntial Final

1

2

3

4

5

6

7

31




Result: The rate constant of the reaction (k) = ________.

The energy of activation (E) =_____________

Experiment-12

ADSORPTION OF CHARCOAL

AIM: To determine the Adsorption of aqueous acetic acid by Activated Charcoal and to study

adsorption isotherm.

APPARATUS: Stopper bottles,

20 ML Pipette,Burette,

Beakers

CHEMICALS: Powdered activated charcoal,

0.5N Glacial acetic acid and 0.1 N NaOH.

PRINCIPLE: Freundlich adsorption isotherm is given by the expression:

x = KC 1/n - equation-1m

Where ‘X’ and m are the amounts of solute (adsorbate) and adsorbent respectively, ‘C’ is theequilibrium concentration of adsorbate. ‘K’ is a constant depends on both, the nature of adsorbent as

well as of adsorbate. “n” is another constant and depends only on the nature of adsorbate.

Taking log, the equation (1) can be written as

log x = log k + 1 log C

m n

When log X is plotted against log C, it gives a straight line whose slope is 1 and the

m n

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Intercept log k.

PROCEDURE:

Proceed stepwise as follow:1. Take 50, 40, 30, 20 and 10 ml of 0.5 N acetic acid in stopped bottles and to these add 0, 10, 20,

30 and 40 ml of distilled water respectively and label them.

2. Transfer 1 gm of activated charcoal to each bottle then shake these vigorously for about one

hour and allow them to stand for half an hour to attain the room temperature.3. Filter off charcoal and while filtering discard initial nearly four ml filtrate in each case.

4. Take 5 ml of each filtrate and titrate it against standard solution of 0.1 N NaOH using

phenolphthalein as an indicator.5. Note the reading in each case.

OBSERVATIONS:

1 .room temperature =. . . . . . °C

2. Amount of charcoal used in bottle = 1g3. Volume of solution taken for titration each time = 5 ml

Bottle No

Volume of 0.5 NCH3COOH (ml)

Volume of water added

Initialnormality of the

acid (normality)

C2

Volume of NaOH used, V

1

23

4

5

50

4030

20

10

0

1020

30

40

0.50

0.400.30

0.20

0.10

Calculate the normality of the acid after adsorption using N1V1 = N2V2. Subtract this value frominitial normality of the acid. This will give you the normality of the acid adsorbed. Let it be N.

The amount of the acid adsorbed, x = N X 60 gm

1000

m = 1g in all cases

Repeat the calculation of remaining solutions and produce your results in tabular form as below:

Bottle

number

Initial

normalityacid

Normality of

acid adsorbed

Amount of

acid adsorbedx

x / m log x / m log C

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1

2

34

5

0.50

0.40

0.300.20

0.10

Plot the graph between x/m and log C. The slope is equivalent to 1 / n and the intercept to log k.

RESULT: The trend of the graph is in accordance with Freundlich adsorption isotherm. The values of

1 and ‘k’ are respectively……. and……. n

PRECAUTIONS:

1. Shake all the solutions properly and uniformly2. Filter the solution before proceeding for titration and discard the initial small volume of the

filtrate.

3. Do not use wet filter paper in filtration as it may dilute the solution.

Documents

Engineering Chem 24092009