Question

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Maximum Useful Work from a Fuel Cell. What is the maximum useful work which can be obtained from a hydrogen-oxygen fuel cell that produces 1.69 kg of water at 25°C? (Assume 1 atm pressure for the gases.)

Answer 1

Formula: $\Delta$G = -w = -nFE^o_cell

Where 'n' is the no. of moles of electrons transferred in the cell reaction = (1690 g/18 g.mol^-1)*2 = 187.778 mol

F = Faraday's constant = 96485.33 C/mol

E^o_cell is the standard cell potential = 1.23 V

Now, w = 187.778 mol * 96485.33 C/mol * 1.23 V

Therefore, the useful work (w) = 22284.9 kJ

Note: 1 CV = 1 J, and 1 kJ = 1000 J