Question

A student adds a few drops of ethanoic acid to test tubes X, Y and Z containing aqueous solutions of sodium chloride, sodium hydroxide and sodium carbonate, respectively. If he now brings a burning splinter near the mouth of the test tubes immediately after adding ethanoic acid in each one of them, in which of the test tube or test tubes the flame will be extinguished?

(A) X and Y

(B) Y and Z

(C) X and Z

(D) only Z

Answer 1

The chemical reactions in test tubes X, Y and Z can be written as:-

Test tube X:-

CH₃COOH + NaCl →No reaction

Test tube Y:-

CH₃COOH + NaOH →CH₃COONa + H₂O

Test tube Z:-

2 CH₃COOH + Na₂CO₃ →2 CH₃COONa + CO₂ + H₂O

Thus, the flame will be extinguished when test tube Z is brought near a burning splinter due to evolution of carbon dioxide gas, which does not support combustion.

Hence, the correct option is D.