Practical 1 of 5 : Calibration of Balance, Pipette and Burette
Introduction:
Balance, volumetric pipette and burette are common glassware for
quantitative analysis at level3. Balance should be calibrated often for accurate
measurements of masses.
Pipettes are a type of lab equipment used to measure and transfer very small
volumes of liquid. Accuracy in pipette measurement is necessary as any
discrepancy in volumes dispensed can affect the results of an experiment.
Burette is needed in many different types of titrations. The calibration process
helps to check whether the equipment is dispensing the proper volumes so it
can be fixed if it is not.
Purpose:
The purpose of this experiments is to measure the volume of liquid and
compare it to the readings obtained from each trial of volumetric glassware.
The materials:
10cm3 of measuring cylinder
25cm3 volumetric pipette
Burette and stand
1 small beaker
1 small conical flask
Distilled water
Balance
Procedure:
1. Calibration of a measuring cylinder
- Zero the balance.
- Weigh a small beaker. Record its mass on the Table.
- Use measuring cylinder to measure 10 cm3 of water. Pour this volume into the small
beaker and weigh the beaker with water in it. Record its mass on the Table.
- Take this small beaker out of the balance. Zero the balance.
- Put the beaker with water back on balance. Record its mass on the Table.
,- Take this small beaker out of the balance. Zero the balance again.
- Put the beaker with water back on balance. Record its mass again on the Table.
- Repeat the weighing of beaker containing water 4 more times. Remember to zero the
balance before putting the beaker back on the balance.
2. Calibration of a volumetric pipette
- Use a clean 25 cm3 volumetric pipette and distilled water.
- Record the room temperature.
- Use an analytical balance to weigh a small clean conical flask with a rubber stopper in
the neck and record the mass of (conical flask + stopper) onto the Table.
- Use the 25 cm3 volumetric pipette to deliver a volume of 25 cm3 distilled water into this
small flask. Put rubber stopper on and reweigh this flask. Record the total mass. Work
out the mass of water only and record it on the Table.
- Pour the water into the sink.
- Repeat steps
- Record all masses onto the Table.
- Repeat steps and 4 more times.
- Work out the average mass of water.
3. Calibration of a Burette
- Record the room temperature. Use the temperature-equilibrated water to fill
the burette past the 0 cm3 mark. Ensure that no air bubbles are trapped in the tip
or any part inside the burette.
- Allow the water to drain to a big waste beaker to get the exact 0.00 cm3 mark
on burette.
- Touch the side of the tip to the beaker to remove any water sticking to the tip.
- Weigh a small conical flask. Record its mass.
- Put the weighed small conical flask under the burette and slowly transfer 10
cm3 of water to this conical flask. Weigh this flask containing 10 cm3 of water.
Record the total mass on the Table.
- Discard the water into the sink.
- Repeat steps and four more times.
- Record all the masses on the Table.
- Perform calculations as you did for pipette.
Table of results: Calibration of a weighing balance for quantitative analysis
Mass of beaker 32.3077 ~ 32.31
only (grams)
, Trials Mass of beaker Mass of water Mean (average) mass
+10 cm3 of water only of beaker + 10 cm3 of
water (grams)
1st time 41.9014 9.5914 Mass of water/ 6
2nd time 41.9004 9.5914 = 57.5367/6
3rd time 41.8990 9.5904 = 9.58945
4th time 41.8984 9.5884 ~ 9.59
5th time 41.8981 9.5881
6th time 41.8970 9.587
Table of results: Calibration of a volumetric Pipette for quantitative analysis
Calibration of a 25 cm3 volumetric Pipette
Temperature recorded: 21.5
Density of water at this temperature = 0.997
Trials Mass of Mass of Mass of 25 Mean mass Mean volume
flask + flask + cm 3 water of 25 cm3 of water
stopper stopper + only water worked out
(grams) 25 cm3 (grams) (grams) from mean
water mass
(grams) V=mass/
density
1st time 63.2198 88.2373 25.0175
2nd time 63.1828 87.9470 24.7642 =24.90472 V=
3rd time 63.1777 87.2299 24.0522 ~ 24.90g 24.90/0.997
4th time 63.1686 88.627 25.4941 =24.975cm3
5th time 63.1618 88.3574 25.1956
Table of results: Calibration of a Burette for quantitative analysis
Calibration of Burette
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