Question
Chemistry Question on p -Block Elements
A crystalline solid X reacts with dil.HCl to liberate a gas Y.Y decolourises acidified KMnO4. When a gas ′Z′ is slowly passed into an aqueous solution of Y, colloidal sulphur is obtained. X and Z could be, respectively
A
Na2SO4,H2S
B
Na2SO4,SO2
C
Na2S,SO3
D
Na2SO3,H2S
Answer
Na2SO3,H2S
Explanation
Solution
Na2SO3(X) reacts with dil. HCl to liberate SO2 gas (Y).
This SO2 gas decolourises acidified KMnO4. On passing H2S gas (Z) into aqueous solution of SO2 (i.e., H2SO3 ), colloidal sulphur is obtained.
Complete reactions are as follows
Purple2KMnO4+2H2O+(Y)5SO2⟶K2SO4+Colourless2MnSO4+2H2SO4
H2O+(Y)SO2⟶Aqueous solution of YH2SO3
H2SO3+(Z)2H2S⟶Colloidal sulphur2S+3H2O