Question

Predict the half-cell reactions that occur when aqueous solutions of the following salts are electrolyzed in a cell with inert electrodes. What is the overall cell reaction in each case?

A) anode reaction for LiCl

B)cathode reaction for LiCl

C)overall cell reaction for LiCl

D)anode reaction for CuSO4

E)cathode reaction for CuSO4

F) overall cell reaction for CuSO4

G) anode reaction for K2SO4

H) cathode reaction for K2SO4

I) overall cell reaction K2SO4

Answer 1

Principle :   The element with Higher SRP value acts as Cathode and

The element with lower SRP value acts as Anode

1) LiCl : E^o_Li⁺/Li = -3.05 V Deposition potential order for Anions is  

E^o_H⁺/1/2H2 = 0.00 v OH^- > I^- > Br^- > Cl^- > No₃^- > SO₄^-2 > F^-

At Anode : ( Li(s) ---------------> Li⁺_(aq) + e^- ) x 2

At Cathode : 2Cl^-_(aq) ----------------> Cl_2(g) + 2e^-

The overall Reaction is : 2 Li_(s) + 2 Cl^-_(aq) -----------> 2Li⁺_(aq) + Cl_2(g)

2) CuSO₄ :   E^o_Cu⁺²/Cu = +0.34 v

   E^o_H⁺/1/2H2 = 0.00 v   D.P of OH^- > D.P of SO₄^-2

At Cathode : Cu⁺²_(aq) +2e^- ------------> Cu_(s)

  At Anode _{: 2 OH}^-_{(aq) ------------> H2O(l) + 1/2 O2(g) + 2e^-}   

The Overall reaction is : Cu⁺²_(aq) + 2OH^-_(aq)-------------> Cu_(s) + H₂O(l) +1/2 O_2(g)

3) K₂SO_{4 :}E^o_{K⁺/ K} = -2.92 V

   E^o_H⁺/1/2H2 = 0.00 v   D.P of OH^- > D.P of SO₄^-2

   At Cathode : 2H⁺_(aq) + 2e^- --------------> H_2(g)

At Anode _{: 2 OH}^-_{(aq) ------------> H2O(l) + 1/2 O2(g) + 2e^-}  

Overall reaction is : 2H⁺(g) +2 OH^-_(aq) -------------> H_2(g) +1/2 O2_(g) + H₂O_(l)