Calibration of Laboratory Glasswares

Question 1

Correction of values to 20 C

Answer 1

V at 20 C = V[1 + 0.000025 (20-t)]

Question 2

Glass at 25 C

Answer 2

1.0002 L

Question 4

Water at 15 C

Answer 4

1.000 L

Question 5

What are the commonly used volumetric glasswares in the laboratory?

Answer 5

Mohr pipette
Serological pipette
Ostwald-Folin
Volumetric transfer pipette

Question 8

To check accuracy

Answer 8

Wt. Hg in pipette/wt. 1 mL Hg at temp. of calibration

Question 9

Why must corrections be made?

Answer 9

Glass and water expand with temperature

Question 10

Glass at 15 C

Answer 10

1.000 L

Question 11

Water at 25 C

Answer 11

1.0002 L

Question 12

How will you ensure that the volume contained or delivered by an instrument is exactly the amount indicated by the graduation mark?

Answer 12

Obtain a calibration certificate

Question 15

Steps in calibrating pipettes

Answer 15

1 Weigh a clean, small, stoppered flask or beaker to the nearest 0.1 mg.
2 Fill the clean pipette with distilled water up to the mark and deliver the water into the weighed flask.
3 Stopper flask and weigh.
4 From the weight and temperature of the water, compute the true volume delivered by the pipette.
5 The correction is the difference between the true and nominal values.
6 Empty the flask and repeat the calibration. Duplicate results should agree within 1 part per 1000 (0.1 mL in 10)

Question 19

Steps in calibrating volumetric flasks

Answer 19

1 Weigh a clean, dry flask in an analytical balance. Record up to 0.1 mg.
2 Remove the flask and fill with distilled water just to the mark and reweigh.
3 From the weight and temperature of the water, compute the true volume of the flask.

Question 22

Used for accurately measuring liquids by volume

Answer 22

Volumetric glassware