Explain the term electrolysis. Write the reactions at cathode ad anode when following substances are electrolysed: (i) molten NaCl (ii) aqueous solution of NaCl (iii). Molten lead bromide (iv) Aq. `H_(2)SO_(4)`

Explanation

Electrolysis is process in which an electrolyte is broken down into simple substances by passing electric current through it in molten state or in aqueous solution.
(i). `underset(("molten"))(NaClto)Na^(+)+Cl^(-)`
At cathode `Na^(+)+e^(-)toNa" ""anode"' "Cl^(-)-e^(-)toCl`
`Cl+CltoCl_(2)`
(ii). `NaCl(aq)toNa^(+)(aq)+Cl^(-)(aq)," "H_(2)O(l)toH^(+)(aq)+OH^(-)(aq)`
At cathode `2H^(+)+2e^(-)toH_(2)(g), " ""anode"" 2Cl^(-)-2e^(-)toCl_(2)(g)`
(iii). `underset(("molten"))(PbBr_(2)to)Pb^(2+)+2Br^(-)`
At cathode `Pb^(2)+2e^(-)toPb," ""anode" " 2Br^(-)-2e^(-)toBr_(2)`
(iv). `H_(2)SO(aq)to2H^(+)(aq)+SO_(4)^(2-)(aq)," "H_(2)O(l)toH^(+)(aq)+HO^(-)(aq)`
At cathode `2H^(+)(aq)+2e^(-)to_(2)(g)`
at anode `2OH^(-)(aq)toO_(2)(g)+2H^(+)(aq)+4e^(-)`