During the discharge of a lead storage battery, the density of sulphuric acid fell from 1.294 to 1.139 g//mL. Sulphu

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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)
JEE 1986

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