A white precipitate was formed when BaCl2(aq) was added to an aqueous solution of a salt X. The precipitate dissolved in dilute HCl with rapid effervescence. Salt X is likely to contain

A. SO₄ ²⁻ ions
B. SO₃ ²⁻ ions
C. NO₃⁻ ions
D. SO₃ ²⁻ ions

Correct Answer:

Option D – SO₃ ²⁻ ions

Explanation

Effervescence is the formation of gas bubbles in a liquid by a chemical reaction. An example of effervescence is the release of carbon dioxide which bubbles as a gas from the liquid when limestone chips, which are composed of calcium carbonate, are added to dilute hydrochloric acid.