Electrolysis of a molten salt with the formula MCl,using a current of 3.86 A for 16.2 min,deposits 1.52 g of metal.Identify the metal.(1 faraday = 96,485 coulombs)

Question

Quizplus · Accepted Answer

We can use Faraday's laws of electrolysis to determine the amount of metal deposited and therefore identify the metal. 
First, we can calculate the total charge that passed through the electrolytic cell:

Q = It = (3.86 A)(16.2 min x 60 s/min) = 3725.52 C

Next, we can use the stoichiometry of the reaction to relate the amount of metal deposited to the charge passed:

1 mol M = 1 F = 96,485 C
molar mass M = m/n = 1.52 g / (M/MCl)
n = Q/F = 3725.52 C / 96,485 C/mol = 0.0386 mol
M = m/n = 1.52 g / 0.0386 mol = 39.38 g/mol

Looking at the periodic table, the only alkali metal with a molar mass close to 39.38 g/mol is potassium (K), which has a molar mass of 39.10 g/mol. Therefore, the answer is E, K.

Electrolysis of a Molten Salt with the Formula MCl,using a Current