# Fuel Cell

Fuel Cell  is a galvanic cell in which fuel are $H_2, O_2, CH_4$ etc.

Electrodes: Porous carbon impregnated with gaseous catalyst like $H_2, or O_2$.

Electrolyte: Aqueous KOH (concentration)

Here fuels undergo combustion to give electric energy.

E.g. : $H_2- O_2$ fuel cell:

At anode: $2H_2(g) + 4OH^-(aq.) \to 4H_2O(l) + 4e^-$

At cathode: $O_2(g) + 2H_2O(l) + 4e^- \to 4OH^-(aq.)$

Net reaction: $2H_2(g) + O_2(g) \to 2H_2O(l)$

Requirements:

It should be compact, light, etc.

Astronauts use $H_2- O_2$ fuel cell.

It is pollution free, continuous source of high efficiency.

Example:

A 100 watt, 110 volt incandescent lamp is connected in series with an electrolyte cell containing cadmium sulphate solution. What mass of cadmium will be deposited by the current flowing for 10 hours?

Solution:

$\text{Current} E =\dfrac{\text{watt}}{\text{ Volt}} = \dfrac{100}{110}$

$\text{Amount of electricity} = \text{Current} \times \text{time}$

$Q = \dfrac{100}{110} \times 10 \times 3600 = 32727 C$

Atomic mass of Cd = 1712.4 and valency of Cd = 2

$\therefore$ Equivalent mass = $\dfrac{112.4}{2} = 56.2$

$\therefore$ Mass of Cd deposited = $\dfrac{Q \hspace{2mm} X \hspace{2mm} \text{Equi. Mass}}{\text{Faraday}}$

$\dfrac{32727 \times 56.2}{96500} = 19.06 g$

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