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Fuel cells : Fuel cells are galvanic cel...

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`
What is the value of `DeltaS^(c-)` for the fuel cell at `25^(@)C`?

A

`1944 JK^(-1)`

B

`-163 JK^(-1)`

C

`-1630 JK^(-1)`

D

`1.944 JK^(-1)`

Text Solution

Verified by Experts

The correct Answer is:
B
`Delta G = Delta H- T Delta S`
or `Delta S = (Delta H - Delta G)/(T)`
`= (-258.8 - (-237.2))/(298) = (-48.6)/(298)`
`=- 0.163 kJ K^(-1) mol^(-1)`
`= -163 J K^(-1) mol^(-1)`
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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 :

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 Suppose the concentration of hydroxide ioin in the cell is doubled, then the cell voltage will be

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%

The overall reactions of a hydrogen -oxygen fuel cell is

Knowledge Check

  • 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
    `0.41V`
    B
    `0.83V`
    C
    `-0.41V`
    D
    `0.83V`

  • A fuel cell is

    A
    the voltaic cells in which discontinuous supply of fuels are send at anode to give oxidation
    B
    the voltaic cell in which fuels such as : `CH_(4) , H_(2) , CO` are used up at anode
    C
    it involves the reactions of `H_(2) - O_(2)` fuel cell such as
    Cathode : `2 H_(2) + 4OH^(-) to 4 H_(2) O(l) + 4e`
    Anode : `O_(2) + 2 H_(2)O (l) + 4e to 4 OH^(-)`
    D
    the efficiency of a `H_(2) - O_(2)` fuel cell is very low

  • 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 Suppose the concentration of hydroxide ioin in the cell is doubled, then the cell voltage will be

    A
    Reduced by half
    B
    Increased by a factor of 2
    C
    Increased by a factor of 4
    D
    Unchanged