JAMB - Chemistry (1979 - No. 7)
Methanoic acid mixes with water in all proportions and has about the same boiling point as water which of the following methods would you adopt to obtain pure water from a mixture of stand, water and methanoic acid?
fractional distillation
filtration followed by distillation
neutralization with sodium hydroxide followed by distillation
esterification with ethanol followed by distillation
neutralization with sodium hydroxide followed by filtration
Explication
Water added to an acid decreases its pH, hence, methanoic acid and water (azeotropes with very close boiling points) will be more acidic. Hence, addition of sodium hydroxide forms a salt and water. Then filtration can be done easily.