An alloy of lead (valency = 2)–thallium (valency = 1) containing 70% Pb and 30% Tl, by weight, can b — Electrochemistry Chemistry Question
Question
An alloy of lead (valency = 2)–thallium (valency = 1) containing 70% Pb and 30% Tl, by weight, can be electroplated onto a cathode from a perchloric acid solution. How many hours would be required to deposit 5.0 g of this alloy at a current of 1.10 A? (Pb = 208, Tl = 204)
💡 Solution & Explanation
In 5.0 g of the alloy, mass of Pb = $0.70 \times 5.0 = 3.5$ g and mass of Tl = $0.30 \times 5.0 = 1.5$ g. Equivalents of Pb = $(3.5 / 208) \times 2 = 0.03365$ eq. Equivalents of Tl = $(1.5 / 204) \times 1 = 0.00735$ eq. Total equivalents required = $0.03365 + 0.00735 = 0.041$ eq. Total charge $Q = 0.041 \text{ F} = 0.041 \times 96500 \text{ C} \approx 3956$ C. Time $t = Q / I = 3956 / 1.10 \approx 3596$ s. Converting to hours: $3596 / 3600 \approx 1.0$ hour. Therefore, correct answer is 1.