CₙH₂ₙ₊₁-COONa + NaOH →(CaO, Δ) X + Na₂CO₃; if n = 2, what is X?

Think it through first, then pick an option.

Answer and explanation

Correct answer: b C₂H₆

With n = 2 the salt is C₂H₅COONa; removing -COONa leaves C₂H₆.

Why the other options are wrong

a CH₄: CH₄ comes from sodium ethanoate (n = 1); with n = 2 it is C₂H₆.
c C₃H₈: C₃H₈ would keep every carbon; decarboxylation loses one, so C₂H₆.
d C₄H₁₀: C₄H₁₀ has too many carbons; the product has n carbons, here 2, so C₂H₆.