Question

a sample contained a mixture of powdered limestone(calcium carbonate). sugar and wax. What is the correct way to obtain pure sample of sugar?

a)dissolve the mixture in dilute hydrochloric acid, filter and wash residue
b)dissolve the mixture in hexane, filter and evaporate the filtrate
c)dissolve the mixture in water, filter and evaporate the filtrate
d)dissolve the mixture in water, filter and wash residue

and why??

Answer 1

The correct way to obtain pure sample of sugar is by (c) dissolve the mixture in water, filter and evaporate the filtrate.

This is because, sugar is soluble in water but wax and calcium carbonate are both insoluble in water, so the filtrate will be a sugar solution and can be evaporated to obtain pure sugar crystals.