Aqueous solution of a salt (A) forms a dense white precipitate with BaCl ₂ solution. The precipitate dissolves in dilute HCl to produce a gas (B) which decolourises acidified KMnO ₄ solution. A and B respectively are

Step-by-step solution

BaSO ₃(a q)+ BaCl ₂(a q) BaSO ₄+ other product dense white percipitate BaSO ₄+ HCl SO ₂(g)+ other product white ppt. We know that, KMnO ₄ can be decoloured by gas SO ₂ . So, A will be BaSO ₃ and B will be SO ₂ .