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Q 2657801784.     During the discharge of a lead storage battery, the density of sulphuric acid fell from `1.294` to `1.139 g//mL`. Sulphuric acid of density `1.294 g//mL` is `39% H_2SO_4` by weight and that of density `1.139 g//mL` is `20% H_2SO_4` by weight. The battery holds `3.5 L` of the acid and the volume remained practically constant during the discharge.
Calculate the number of ampere-hours for which the battery must have been used. The charging and discharging reactions are
` Pb + SO_4^(2-) = PbSO_4 + 2e^-` (charging)
`PbO_2 + 4H^(+) + SO_4^(2-) + 2e^-`
`= PbSO_4 + 2H_2O` (discharging)
(Provided By a Student and Checked/Corrected by EXXAMM.com Team)