a. A solution of ferric chloride acidified with `HCl` is unaffacted when hydrogen is bubbled through it, but gets reduced when zinc is added to acidified solution. Explain.
b. When sodium hydride in fused state is electrolysed, hydrogen is discharged at the anode. Explain.

Explanation

(a) Conc. `H_(2)SO_(4)` reacts with zinc to form `SO_(2)` rather than `H_(2)`
`Zn + 2H_(2)SO_(4)(conc.) overset("Heat")to ZnSO_(4) + SO_(2) + 2H_(2)O`
(b) Ordinary `H_(2)` is less reactive and hence it does not reduce acidified `FeCl_(3)` solution. However, when zinc is added to acidified `FeCl_(3)` , nascent hydrogen thus produced is associated with more energy. Consequently, it is more reactive and hence reduces acidified `FeCl_(3)` solution.
`FeCl_(3) + H_(2) to ` No reaction
`Zn+ H_(2)SO_(4)to ZnSO_(4) + H_(2)^(**)` (nascent hydrogen)
`underset("Yellow")(2FeCl_(3) )+ H_(2)^(**) to underset("Green")(2FeCl_(2))+ 2HCl`