Q11 / 160 · TS EAMCET 2013 · Chemistry

The extent of charge of lead accumulator is determined by

  • A
    amount of $\mathrm{PbSO}_4$ in the battery
  • B
    amount of $\mathrm{PbO}_2$ in the battery
  • Correct answer
    C
    specific gravity of $\mathrm{H}_2 \mathrm{SO}_4$ of the battery
  • D
    amount of $\mathrm{Pb}$ in the battery

Solution

In a fully charged lead accumulator or lead storage battery, sulphuric acid has a specific gravity (i.e., density that varies from 1.260 to 1.285. But during discharge (i.e., when the battery is in use). $\mathrm{H}_2 \mathrm{SO}_4$ is used up. $$ \begin{array}{r} \mathrm{Pb}(s)+\mathrm{PbO}_2(s)+4 \mathrm{H}^{+}(a q)+2 \mathrm{SO}_4^{2-}(a q) \longrightarrow \\ 2 \mathrm{PbSO}_4(l)+2 \mathrm{H}_2 \mathrm{O} \end{array} $$ As a result, the specific gravity of $\mathrm{H}_2 \mathrm{SO}_4$ falls when it falls below 1.230 the battery needs recharging.

Hence, the correct answer is option: 'C'.

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