Question

Write the Nernst equation and emf of the following cells at 298 K: (i) Mg(s) | Mg2+(0.001M) || Cu2+(0.0001 M) | Cu(s) (ii) Fe(s) | Fe2+(0.001M) || H+(1M)|H2(g)(1bar) | Pt(s) (iii) Sn(s) | Sn2+(0.050 M) || H+(0.020 M) | H2(g) (1 bar) | Pt(s) (iv) Pt(s) | Br2(l) | Br−(0.010 M) || H+(0.030 M) | H2(g) (1 bar) | Pt(s).

Answer 1

Answer:

(i) E o =0.34−(−2.37)=2.71 V

E=E 0 − n0.059

log [Cu 2+ ]

[Mg 2+ ]

E=2.71−

2

0.059

log

(0.0001)

0.001

E=2.6805 V

(ii) E

o

=0−(−0.44)=0.44 V

E=E 0 − n0.059

log

[H + ] 2

[Fe 2+ ]

E=0.44−

2

0.059

log

(1)

2

0.001

E=0.5285 V

(iii) E

o

=0−(−0.14)=0.14 V

E=E 0 − n0.059

log

[H + ] 2

[Sn 2+ ]

E=0.14− 20.059

log

(0.020) 2

0.050

E=0.08 V

(iv) E

o

=0−1.08=−1.08 V

E=E

0

−

2

0.059

log

[Br

−

]

2

[H

+

]

2

1

E=−1.08−

2

0.059

log

(0.01)

2

(0.030)

2

1

E=−1.288 V