Hydrogen can be prepared by the action of dil H_(2)SO_(4) on

1.	Hydrogen can be prepared by the action of dil H_(2)SO_(4) on
Answer» copper IRON lead mercury Solution :`Cu(E_(Cu^(2+)//Cu)^(@)=+0.34 V)` and`HG(E_(Hg^(2+)//Hg)^(@)=+0.80 V)` lie above `H_(2)` in the ELECTROCHEMICAL series and hence do not react with dil. `H_(2)SO_(4)` to evolve `H_(2)` gas . Although `PB(E_(Pb^(2+)//Pb)^(@)=-0.13V)` lies below `H_(2)` in the electrochemical series, it reacts with dil. `H_(2)SO_(4)` in the begining to EVOLVES `H_(2)` gas but `PbSO_(4)` produced during the reaction forms a `Pb+ H_(2)SO_(4)("dil.") to underset("In soluble")(PbSO_(4))(s) + H_(2)(g)` protective layer around the unreacted Pb and the reaction stops. Only iron `(E_(Fe^(2+)//Fe)^(@)==0.44V)` reacts readily with dil. `H_(2)SO_(4)` to evolve `H_(2)` gas.

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