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?

• only A

• A and B

• B and C

• A and D

D.

A and D

The chemical reaction between ethanoic (acetic) acid and sodium carbonate is:
2CH₃COOH + Na₂CO₃ → 2 CH₃COONa + CO₂ + H₂O
On passing CO2 gas through lime water, the lime water turns milky. The milky appearance 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 considered as a correct test of acetic/ethanoic acid.
Reaction:
2 CH₃COOH + Ca(OH)₂ → (CH₃COO)₂Ca + 2H₂O

Hence, the correct answer is the option (d).