Question

A pipet is calibrated to deliver 10.00 ml of water. Discuss the possible error if this pipet were used to deliver a) concentration H2So4

b) Acetone

c) Mercury

Hint: Consider density( as it relates to the amount of solution left in the tip) and meniscus shape. Also, consider evaporation problems if the weighing bottle is not immediately capped.)

Answer 1

A pipet is calibrated to deliver 10.00 ml of water (density 1.0 g/ml).

The possible error if this pipet were to deliver,

a) concentrated H2SO4 (density 1.84 g/mo) = since the density of the liquid is much greater, chances of some amount of liquid left in the pipet after it is used to transfer concentrated H2SO4 increases, hence the error in meaurment would be large.

b) Acetone (density 0.784 g/ml) : has density lower than water, so all the liquid pipetted out cannot be easily transferred to the other container. Also, owing to the low boiling point of acetone, chances of evaporation also remains If the liquid is not transferred immediately.

c) Mercury (density 13.69 g/ml) : has much higher density. It can be easily transferred to the other container with much lower error in meaurement.