Question

You have four test tubes, A, B, C and D containing sodium carbonate, sodium chloride, lime water and blue litmus solutions respectively. Out of these the material of which test tube/ test tubes would be suitable for the correct test of acetic/ethanoic acid?

(a) only A
(b) A and B
(c) B and C
(d) A and D

Answer 1

Ethanoic (acetic) acid is an acid, and it will change blue litmus solution to red.
The chemical reaction between ethanoic (acetic) acid and sodium carbonate is:
2 CH₃COOH + Na₂CO₃ → 2 CH₃COONa + CO₂ + H₂O
On passing CO₂ gas through lime water, the lime water turn milky. The milky apprearance of lime water is due to the formation of solid calcium carbonate (CaCO₃).
Reaction:
Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

Therefore, out of four test tubes A, B, C and D, only A and D test tubes would be suitable for the correct test of acetic/ethanoic acid.

Acetic acid also reacts with lime water to give calcium acetate (CH₃COO)₂Ca) as a product. But here it is not consider as correct test of acetic/ethanoic acid.
Reaction:
2 CH₃COOH + Ca(OH)₂ → (CH₃COO)₂Ca + 2 H₂O

Hence, the correct answer is option (d).