Question

Assertion :$H_2+O_2$ fuel cell gives a constant voltage throughout its life. Reason: In this fuel cell, $H_2$ reacts with $O{H}^{-}$ ions, yet the overall concentration of $O{H}^{-}$ ions does not change.

• A.

  assertion is true, reason is true; reason is correct explanation for assertion.

• B.

  assertion is true, reason is true; reason is NOT a correct explanation for assertion.

• C.

  assertion is true, reason is false.

• D.

  assertion is false, reason is true.

Answer 1

The correct option is A

assertion is true, reason is true; reason is correct explanation for assertion.

It is possible to make batteries in which the reactants are fed continuously to the electrodes. Electrical cells that are designated to convert the free energy from the combustion of fuels such as hydrogen, carbon monoxide or methane directly into electrical energy are called FUEL CELLS. One of the most successful fuel cells uses the reaction of hydrogen with oxygen to form water (fig.). This cell has been used for electric power in the Appollo space programme. The water vapour produced was condensed and added to the drinking water supply for the astronauts.

In the cell (fig.) hydrogen and oxygen are bubbled through a porous carbon electrode into concentrated aqueous sodium hydroxide. Catalysts are incorporated in the electrode. The electrode reactions are :

Anode $2\left[H_2\right(g)+2O{H}^{-}(aq)\to 2H_{2}O(l)+2e^{-}]$

Cathode $O_2\left(g\right)+2H_{2}O\left(l\right)+4e^{-}\to 4O{H}^{-}\left(aq\right)$

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Overall reactions : $2H_2\left(g\right)+O_2\left(g\right)\to 2H_{2}O\left(l\right)$

This cells runs continuously as long as the reactants are supplied.