When a solution of a certain gadolinium salt is electrolyzed with a current of 1.0 A for 2.0 h, 0.025 mol of Gd metal forms. Calculate the charge on the gadolinium ion in the salt.

Question

Quizplus · Accepted Answer

First, we need to calculate the number of electrons transferred in the electrolysis reaction:

1 A for 2.0 h = 7200 C

Faraday's constant = 96,485 C/mol e-

Number of electrons = 7200 C / (96,485 C/mol e-) = 0.0745 mol e-

Since each Gd ion gains 3 electrons to form Gd metal, the number of moles of Gd ions reduced is 0.025 mol e- / 3 mol e-/ion = 0.00833 mol Gd3+

The charge on the Gd ion can be determined using the following equation:

Charge = (moles of electrons transferred) / (moles of ions reduced)

Charge = (0.0745 mol e-) / (0.00833 mol Gd3+) = 8.94 ≈ 9

Therefore, the charge on the gadolinium ion is +3, and the best choice is B.

When a Solution of a Certain Gadolinium Salt Is Electrolyzed