EMF of an `H_(2)-O_(2)` fuel cell

For a H_(2) - O_(2) fuel cell , the theoretical voltage has been found to be 1.23 V and Delta H to be -285 kJ mol^(-1) . The efficiency of the fuel cell is

What are fuel cells ? Explain the electrode reactions involved in the working of H_(2) - O_(2) fuel cell.

Fuel cells : Fuel cells are galvanic cells in which the chemical energy of fuel cell is directly converted into electrical energy. A 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 and hydrogen are continuously fed into the cell. Hydrogen gets oxidized to H^(o+) which is neutralized by overset(c-)(O)H, i.e., anodic reaction. At cathode, O_(2) gets reduced to overset(c-)(O)H Hence, the net reaction is The overall reaction has DeltaH=-285.6 kJ mol^(-1) and DeltaG=-237.4 kJ mol^(-1) at 25^(@)C If the cell voltage is 1.23V for the H_(2)-O_(2) fuel cell and for the half cell :

(a) What are fuel cells ? Explain the electrode reactions involved in the working of H_(2)-O_(2) fuel cell. (b) Represent the galvanic cell in which the reaction Zn(s) + Cu^(2)(aq) to Zn^(2+) (aq) + Cu(s) takes place.

Fuel cells : Fuel cells are galvanic cells in which the chemical energy of fuel cell is directly converted into electrical energy. A 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 and hydrogen are continuously fed into the cell. Hydrogen gets oxidized to H^(o+) which is neutralized by overset(c-)(O)H, i.e., anodic reaction. At cathode, O_(2) gets reduced to overset(c-)(O)H Hence, the net reaction is The overall reaction has DeltaH=-285.6 kJ mol^(-1) and DeltaG=-237.4 kJ 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 voltaci 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)O+4overset(c-)(O)H rarr 4H_(2)O(l)+4e^(c-) Cathode : O_(2)+2H_(2)O(l) =4e^(-) rarr 4overset(c-)(O)H IV. The efficiency of H_(2)-O_(20 fuel cell is 70 to 75%

Draw a neat and labelled diagram for H_(2)-O_(2) fuel cell. Write the reaction which occurs at cathode of the cell.