Compounds A and B are treated with dil. HCl separately. The gas liberated are Y and Z respectively. Y turns acidified K 2 C r 2 O 7 paper green while Z turns lead acetate paper black. The compounds A and B are respectively.

Step-by-step solution

Here A & ( B ) are N a 2 S O 3 a n d N a 2 S respectively. N a 2 S O 3 ( A ) + 2 H C l → 2 N a C l + S O 2 ( Y ) + H 2 O K 2 C r 2 O 7 + H 2 S O 4 + 3 S O 2 → K 2 S O 4 + C r 2 ( S O 4 ) 3 G r e e n + H 2 O N a 2 S ( B ) + 2 H C l → 2 N a C l + H 2 S ( Z ) P b C H 3 C O O 2 + H 2 S → P b S B l a c k + 2 C H 3 C O O H