Which of the following will not produce hydrogen gas?
Reaction of Zn with concentrated H2SO4
Water on electrolysis decomposes into H2 and O2 gases.
In Nelson's cell, aqueous NaCl is electrolyzed where:
The reaction at the cathode is:
H2O(l)+2e−→H2+2OH−
The reaction at the anode is:
Cl−→12Cl2(g)+1e−
The overall reaction is as follows:
NaCl(aq)+H2O(l)→Na+(aq)+OH−(aq)+H2(g)+1/2Cl2(g)
Zn on reacting separately with excess dil H2SO4 and excess NaOH liberates H2(g)
Zn+2NaOH→Na2ZnO2+H2
Zn+H2SO4(dil.)→ZnSO4+H2
But when Zn reacts with concentrated H2SO4,
4Zn+5H2SO4(moderately strong and hot)→4ZnSO4+H2S+4H2O
3Zn+4H2SO4(moderately strong and hot)→3ZnSO4+S+4H2O
Zn+2H2SO4(conc.)→ZnSO4+SO2+2H2O