Question

The following reactions take place in a galvanic cell:

(i) Cu²⁺_(aq)+ Ni _(s)→ Cu_(s) + Ni²⁺_(aq)

(ii) 2Ag⁺ (aq) +H2 (g) → 2Ag(s) +2H⁺ (aq)

(iii) Cl2 (g) + Sn²⁺ (aq) → Sn⁴⁺ (aq) + 2Cl^- (aq)
(a) For each of the above spontaneous cell reactions, write the electrochemical cell using standard cell notation.

(b) Use the standard reduction potentials below to evaluate E^Ɵcell for the overall cell reaction taking place in (iii):

Cl2(g) + 2e^- → 2Cl^- (aq) E = +1.36V

Sn⁴⁺(aq) +2e^- →Sn²⁺ (aq) E =+0.15V

Answer 1

(a)

In standard cell notation, anode is on the left and cathode is on the right. Oxidation takes place at anode.

So the standard cell notations are:

(i)

Ni(s) | Ni²⁺(aq) || Cu²⁺(aq) | Cu(s)

(ii)

H₂(g) | H⁺(aq) || Ag⁺(aq) | Ag(s)

(iii)

Sn²⁺(aq) | Sn⁴⁺(aq) || Cl-(aq) | Cl₂(g)

(b)

E⁰cell = Eoxid + Ered

In (iii) reaction above, we see that oxidation reaction is:

Sn2+ (aq) ---> Sn4+(aq) + 2e-

So, Eoxid = -0.15 V

Reduction reaction is:

Cl2(g) + 2e- → 2Cl- (aq);

So, Ered = +1.36V

So,

E⁰cell = -0.15+1.36 = 1.21 V