Question

Which type of glassware would most accurately deliver a 15.00 mL liquid sample? A.volumetric pipette B.graduated cylinder C.eye dropper D.50mL beaker E.volumetric flask

Answer 1

Liquids are the form of matter that have definite volume but no definite shape. The volume of a liquid can be defined as the space in which it is kept. Volume measurements of any liquid can be done by using specific glass wares in the laboratory.

When a liquid is filled in any glassware, it forms a meniscus at the top of the surface because the difference in the force of the attraction of the molecules with themselves and the molecules with the surroundings.

An example is shown below:

The correct way to see the reading is to see perpendicular to the base of the meniscus.

From the diagram,

The upper eye corresponds to low value of reading and the lower eye corresponds to high value of reading. Middle one will corresponds to the correct reading.

The more the width in which the liquid is taken, the large will be the meniscus and less accurate is the reading.

C. Eye dropper: They are used to measure drops. They are used where small amounts of the liquids is used. Drops are the rough idea for the liquid to be used and can't be used to measure volume accurately.

D. 50 mL beaker: Beakers are very inaccurate when it comes for the measurement of the volume of the liquids. They are only used when the volume is very very high. This is because of large meniscus.

B. Graduated cylinder: They are a quick way for measuring volumes of liquid but a less accurate way. They are used to prepare large stock solutions.

E. Volumetric flask: They are very best used to measure volumes accurately. They have a mark on their neck and measure the exact volume. To measure 15 mL, we cant use it because they are generally available with sizes starting from 100 mL, 250 mL and so on.

A. Volumetric pipette: They are a simple and very accurate way for measuring liquids. They are so accurate because they have a very thin neck and meniscus can be seen easily as it becomes almost flat in the neck. They comes with different measurement volumes and volumes are marked on the glassware. 15 mL can be easily and accurately measured by using volumetric pipette.

Answer- A