During the discharge of a lead storage battery

CHEMISTRY · Subjective · AP · Chemistry · Thermodynamics and Electrochemistry · Thermodynamics and Electrochemistry

Problem

During the discharge of a lead storage battery, the density of sulphuric acid fell from 1.294 g mL−11.294 \text{ g mL}^{-1} to 1.139 g mL−11.139 \text{ g mL}^{-1}. Sulphuric acid of density 1.294 g mL−11.294 \text{ g mL}^{-1} is 39% by mass and that of density 1.139 g mL−11.139 \text{ g mL}^{-1} is 20% by mass. The battery holds 3.5 litre of acid and the volume practically remained constant during the discharge. Calculate the no. of ampere hour for which the battery must have been used. The charging and discharging reactions are: Pb+SO42−→PbSO4+2echarging\text{Pb} + \text{SO}_4^{2-} \rightarrow \text{PbSO}_4 + 2e \quad \text{charging} PbO2+4H++SO42−+2e→PbSO4+2H2Odischarging\text{PbO}_2 + 4\text{H}^+ + \text{SO}_4^{2-} + 2e \rightarrow \text{PbSO}_4 + 2\text{H}_2\text{O} \quad \text{discharging}

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