Activity 1 Lab report Quan.docx

8/14/2019 Activity 1 Lab report Quan.docx

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Activity 1

Calibration of Pipets

Briana Halbert

9/17/2013

Dr. Kimaro


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Purpose:

The purpose of this experiment was to calibrate three different pipets.

Objectives:

The objectives of this laboratory experiment was to learn the usage of volumetric glassware, proper procedures in

transferring solutions, the difference between each pipet, determining the actual volumes of the three different typeof pipets, and how to use an analytical balance.

Procedure:

The introductory sections, Mass Measurements and Volumetric Glassware were referred to, prior to using the

balance and pipets. About 250 mL of deionized or distilled water was placed in a 400 mL beaker. When the

temperature of the water was not at room temperature, it was left to be equilibrated to room temperature. The

temperature of the equilibrated water was recorded using a thermometer. The thermometer was placed in the beakecontaining water, and left in place during the experiment. If the temperature of the water changed during the

experiment, the changed temperature was recorded. The temperature recorded, prior to each mass measurement, wa

used to do calculations.The Erlenmeyer flasks were labeled, 1, 2, and 3. Flask 1 was used with volumetric pipet; flask 2 was used with the

serological pipet; flask 3 was used with the Mohr pipet. A rubber or cork stopper was placed on each flask, and the

flasks were weighed. The masses were recorded.

Upon proceeding to the next step, we practiced using the pipets. The volumetric pipets were allowed to drain into tvessel. The tip of the pipet touched the side of the vessel to remove the last drop. Mohr pipet delivered the volumes

between calibrated marks on the sides. Serological pipet was allowed to completely drain into the vessel, while the

remaining solution was blown into the vessel.The volumetric pipet was filled with room temperature water to the line. And transferred to flask 1. The cleaned

serological pipet delivered the water to flask 2. The Mohr pipet delivered the water to flask 3. Each flask had a cork

stopper placed on it follow by weighing them. The masses were recorded. The necks of the flask were not wet with

water. Each pipet was used with its respectable flask seven more times. After adding the water each time, the flaskwere weighed. The masses were recorded.

Data/ Calculations:

Temperature of distilled water: 22C.

() () Standard Deviation of Flask 1: Volumetric Pipet

() ()

% Standard Deviation


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% Standard Deviation of Flask 1: Volumetric Pipet

Results:

Temperature of distilled water: 22C.

Flask 1: Volumetric Pipet

Volume (mL)Mass of Flask,

stopper & Water(g)Temperature (C)

Mass of Water

Transferred (g)

Calculated

Volume (mL)

0 42.3206 22 0 0

5 47.3474 22 5.0268 5.0429

10 52.3433 22 4.9959 5.0119

15 57.3433 22 5.0133 5.0294

20 62.3497 22 4.9931 5.0091

25 67.3480 22 4.9983 5.0143

30 72.3439 22 4.9959 5.0119

35 77.3262 22 5.0000 5.0161

40 82.3154 22 4.9892 5.0051

Flask 2: Serological Pipet



Mass of Water

Transferred (g)

Calculated

Volume (mL)

0 40.0396 21 0 0

5 45.0615 21 5.0219 5.0370

10 50.0795 21 5.0180 5.0331

15 55.1089 21 5.0294 5.0445

20 60.0030 21 4.8941 4.9088

25 65.0564 21 5.0534 5.0686

30 70.0541 21 4.9977 5.0127

35 75.0756 21 5.0215 5.0366

40 80.0823 21 5.0067 5.0218


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Flask 3: Mohr Pipet



Mass of Water

Transferred (g)

Calculated

Volume (mL)

0 38.4509 22 0 0

5 43.4478 22 4.9969 5.012910 48.4535 22 5.0057 5.0217

15 53.4661 22 5.0126 5.0287

20 58.4639 22 4.9978 5.0138

25 63.4836 22 5.0197 5.0358

30 68.5703 22 5.0867 5.103

35 73.5806 22 5.0103 5.0264

40 78.5928 22 5.0122 5.0283

During the volumetric experiment, the temperature read 22C.

The density was 0.9968 g/mL.

During the Mohr experiment, the temperature was 22C.


During the Serological experiment, the temperature was 21C.


Volumetric Serological Mohr

Standard Deviation 0.0124 0.0479 0.02899

Average (mL) 5.017875 5.0204 5.033825

RSD (%) 0.31% 0.95% 0.58%

Discussion:

The volumetric pipet was the most accurate in measuring the distilled water. Volumetric pipet had the lowe

standard deviation. The serological and Mohr pipets were off by 0.04 and 0.03. After calibrating a 5mL pipet givin

the masses 4.975, 4.9845, 4.9800, and 4.9820g at 26C, the individual volumes of the pipets were 5.0000, 5.0050,

5.0005, and 5.0025. The average volume was 5.0020, and the standard of deviation was 0.0023.

Conclusion:

According to the results of the experiment, the volumetric pipet was the most precise with the lowest standard

of deviation. The serological was the least precise. Therefore, the Mohr pipet was between the volumetric and

Serological with the standard of deviation. Moreover, the conclusion of this experiment was drawn that this lab

experiment is the calibration of the pipets: volumetric, serological, and Mohr pipets are precise but not accurate.

Better measurement and practice of the experiment would have made the experiment more precise.

Documents

Activity 1 Lab report Quan.docx