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JAMB Chemistry 1979 Question 9

Question 9

Separation of Mixtures

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 sand, water and methanoic acid?

  1. A.Fractional distillation
  2. B.Filtration followed by distillation
  3. C.Neutralization with sodium hydroxide followed by distillation
  4. D.Neutralization with sodium hydroxide followed by filtration
  5. E.Esterification with ethanol followed by distillation.
Show the answer and explanation

Answer: C (Neutralization with sodium hydroxide followed by distillation)

Explanation

Because the acid boils at almost the same temperature as water, distillation alone cannot separate them. Neutralising turns the acid into sodium methanoate, a non-volatile salt, so distilling then gives pure water and leaves the salt and sand behind.