1.

In fuel cell H2 and O2 react to produce electricity. In the process, H2 gas is oxidised at the anode and O2 at cathode. If 44.8 litre of H2 at 25°C and also pressure reacts in 10 minutes, what is average current produced? If the entire current is used for electro deposition of Cu from Cu2+ , how many grams of Cu deposited?

Answer»

Oxidation at anode: 

2H2 (g) + 4OH- (aq) → 4H2O (1) + 4e- 

1 mole of hydrogen gas produces 2 moles of electrons at 25°C and 1 atm pressure, 1 mole of hydrogen gas occupies = 22.4 litres

∴no. of moles of hydrogen gas produced = \(\frac{1mole}{22.4litres}\) x 44.8 litres = 2 moles of hydrogen

∴2 of moles of hydrogen produces 4 moles of electro 

i.e., 4F charge. We know that Q = It

I = \(\frac{Q}{t}\,=\,\frac{4F}{10mins}\,=\,\frac{4\times96500}{10x60s}\)

I = 643.33 A

Electro deposition of copper 

Cu2+(aq) + 2e- → Cu(s) 

2F charge is required to deposit 1 mole of copper i.e., 63.5 g 

If the entire current produced in the fuel cell i.e., 4 F is utilised for electrolysis, then 2 x 63.5 i.e., 127.0 g copper will be deposited at cathode.



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