Write the Nernst equation and emf of the following cells at 298 K:

**(i)
** Mg(s) | Mg^{2+}(0.001M)
|| Cu^{2+}(0.0001
M) | Cu(s)

**(ii)
** Fe(s) | Fe^{2+}(0.001M)
|| H^{+}(1M)|H_{2}(g)(1bar)
| Pt(s)

**(iii)
** Sn(s) | Sn^{2+}(0.050
M) || H^{+}(0.020
M) | H_{2}(g)
(1 bar) | Pt(s)

**(iv)
** Pt(s) | Br_{2}(*l*)
| Br^{−}(0.010
M) || H^{+}(0.030
M) | H_{2}(g)
(1 bar) | Pt(s).

**(i)** For the
given reaction, the Nernst equation can be given as:

= 2.7 − 0.02955

= 2.67 V (approximately)

**(ii)** For the
given reaction, the Nernst equation can be given as:

= 0.52865 V

= 0.53 V (approximately)

**(iii)** For the
given reaction, the Nernst equation can be given as:

= 0.14 − 0.0295 × log125

= 0.14 − 0.062

= 0.078 V

= 0.08 V (approximately)

**(iv)** For the
given reaction, the Nernst equation can be given as:

**
**