Question
During the discharge of a lead storage battery, density of H2SO4 fell from 1.294 to 1.139\ g/mL.Sulphuricacidofdensity1.294is39H_{2}SO_{4}byweightandthatofdensity1.139\ g/mLis20H_{2}SO_{4}byweight.Thebatteryhold3.5\ litreoftheacidandvolumeremainspracticallyconstantduringdischarge.Calculateampere−hourofwhichthebatterymusthavebeenused.Thecharginganddischargingreactionsare:Pb + SO_{4}^{2-} \rightarrow PbSO_{4} + 2e^{-}(charging)PbO_{2} + 4H^{+} + SO_{4}^{2-} + 2e^{-}\rightarrow PbSO_{4} + 2H_{2}O$ (discharging).