Help! Thomas Edison was faced with the problem of measuring the electricity that

Question

Help! Thomas Edison was faced with the problem of measuring the electricity that each of his customers had used. His first solution was to use a zinc "coulometer," and electrolytic cell in which the quantity of electricity is determined by measuring the mass of zinc deposited. Only some of the current used by the customer passed through the coulometer. (a) What mass of zinc would be deposited in 1 month (of 31 days) if 1.0 mA of current passed through the cell continuously? (b) An alternative solution to this problem is to collect the hydrogen produced by electrolysis and measure its volume. What volume would be collected at 298 K and 1.00 bar under the same conditions?

Explanation / Answer

charge passed = 31x1xE-3x60x60x24=2678.4 Coulombs =2678.4/F = 0.028 moles of electrons
moles of Zn deposited =0.028 /2 =0.0139 moles
mass of Zn =65.39x0.0139 = 0.908 g

a) moles of H2 collected = 0.0139 moles

b) Volume of H2 =nRT/P = 0.0139 x0.082x298/1 = 0.340 L

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