A car battery uses lead acid chemistry as shown in the reactions below: a. Which
ID: 492271 • Letter: A
Question
A car battery uses lead acid chemistry as shown in the reactions below: a. Which reaction occurs at the anode ___Rx_1 ___Rx_2 ___Both ___neither b. If this battery has a charge rating of 50 amp-hours (can provide 1 amp for 45 hours). Determine the starting mass (kg) of the anode and the cathode for a fresh battery in providing this amount of charge. If a fresh lead-acid battery has 300 g of Pb and 200 g of PbO_2 in its anode and cathode, which material is the limiting reactant, what is the % excess of the other material? If two of the battery described in c) is are connected in series to power a motor which draws 6Amps, how long can the batteries last?Explanation / Answer
(a): Oxidation takes place at anode. In reaction 1, PbO2 (ON of Pb = +4) is reduced to PbSO4 (ON of Pb = +2)
In reaction 2, Pb(s) is oxidized to PbSO4.
Hence Reaction-2 occurs at anode.
(c): Moles of Pb taken in the fresh battery = mass / molar mass = 300 g / 207.2 g/mol = 1.448 mol
Moles of PbO2 taken in the fresh battery = mass / molar mass = 200 g / 239.2 g/mol = 0.8361 mol
From the given reaction it is clear that 1 mol each of Pb and PbO2 react to complete the redox reaction inside the battery.
Since the moles of PbO2 is less than the moles of Pb, PbO2 is the limiting reactant. (answer)
Percentage excess of Pb = [(1.448 - 0.8361) / 0.8361]x100 = 73.2 % (answer)
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