Name: Fuel Cell
Uploaded: 2019-07-19
Duration: 5 min 7 s
Description: Galvanic cells that are designed to convert the energy of combustion of fuels like hydrogen and methane directly into electrical energy are called fuel cells...

Question

Write the Nernst equation and calculate emf of the following cell at $298 K :$
$M g (s) |M g^{2 +} (0.001 M)| |C u^{2 +} (0.0001 M)| C u (s)$

(Given $E_{{Mg}^{+ 2} / Mg}^{\circ} = - 2.36, E_{{Cu}^{+ 2} / Cu}^{\circ} = 0.34$ )

Accepted Answer

For the given reaction, $M g (s) |M g^{2 +} (0.001 M)| |C u^{2 +} (0.0001 M)| C u (s)$

The reaction at the anode : $M g (s) \to M g^{2 +} (a q) + 2 e^{-}$

The reaction at the cathode: $C u^{2 +} (a q) + 2 e^{-} \to C u (s)$

The Nernst equation can be given as:

$E_{c e l l} = E_{c e l l}^{\circ} - \frac{0.0591}{n} \log \frac{[M g^{2 +}]}{[C u^{2 +}]}$

The number of electrons transferred, $n = 2$

$E_{cell} = E_{cell}^{\circ} - \frac{0 .0591}{2} \log \frac{[{Mg}^{2 +}]}{[{Cu}^{2 +}]}$

$E_{cell}^{\circ} = E_{cathode}^{\circ} - E_{anode}^{\circ}$

$E_{cell} = \{0.34 - (- 2.36)\} - \frac{0.0591}{2} \log \frac{0.001}{0.0001}$
$= 2.7 - \frac{0.0591}{2} \log 10$
$= 2.7 - 0.02955$

$= 2.67 V$

Write the Nernst equation and calculate emf of the following cell at $298 K :$
$M g (s) |M g^{2 +} (0.001 M)| |C u^{2 +} (0.0001 M)| C u (s)$

(Given $E_{{Mg}^{+ 2} / Mg}^{\circ} = - 2.36, E_{{Cu}^{+ 2} / Cu}^{\circ} = 0.34$ )

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Write the Nernst equation and calculate emf of the following cell at 298 K: Mgs Mg2+0.001M Cu2+0.0001M Cus (Given EMg+2/Mg∘=-2.36, ECu+2/Cu∘=0.34)