Explain the following : (a) Hydrogen is not prepared by action of concentrated sulphuric acid on zinc. (b) A solution of ferric chloride is unaffected when hydrogen is bubbled through it, but gets reduced when zinc is added to the same acidified solution.

Explain the following : (a) Hydrogen is not prepared by action of conc

1.	Explain the following : (a) Hydrogen is not prepared by action of concentrated sulphuric acid on zinc. (b) A solution of ferric chloride is unaffected when hydrogen is bubbled through it, but gets reduced when zinc is added to the same acidified solution.
Answer» Solution :(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`