Which of the following statements are correct?
Fuel cells are galvanic cells in which the chemical energy of fuel is directly converted into electrical energy. Type of fuel cell is a hydrogen - oxygen fuel cell. It consists of two electrodes made up of two porous graphite impregnated with a catalyst (platinum, silver, or metal oxide). The electrodes are placed in aqueous solution of NaOH. Oxygen nad hydrogen are continuously fed into the cell. Hydrogen gets oxidized to `H^(oplus)` which is neutralized by `overset(Θ)(OH)`, ie., anodic reaction.
`H_(2) hArr 2H^(oplus) + 2e^(-)`
`2H^(oplus) + 2 overset(Θ)(OH) hArr 2H_(2)O`
`H_(2) + 2 overset(Θ)(OH) hArr 2H_(2)O + 2e^(-)`
At cathode, `O_(2)` gets reduced to `overset(Θ)(OH)` i.e., `O_(2) + 2H_(2)O + 4e^(-) hArr overset(Θ)(4)OH`
Hence, the net reaction is `2H_(2) + O_(2) hArr 2H_(2)O`
The overall reaction has `Delta H= -285.6kJ mol^(-1) and Delta G= -237.4kJ mol^(-1) " at " 25^(@)C`
A fuel cell is
I. A voltaic cell in which continuous supply of fuels are sent at anode to perform oxidation
II. A voltaic cell in which fuels such as `CH_(4), H_(2) and CO` are used up at anode.
III. One which involves the reaction of `H_(2)- O_(2)` fuel cell such as: Anode `2H_(2) + 4 overset(Θ)(OH) rarr 4H_(2)O(I) + 4e^(-)`
cathode : `O+ 2H_(2)O(I) + 4e^(-) rarr 4 overset(Θ)(OH)`
IV. The efficiency of `H_(2)-O_(2)` fuel cell is 70 to 75%

Options

A. I, III
B. I, III, IV
C. I, II, III, IV
D. I, II, III

Answer

C