Chemistry HW question

Question

Nickel is a transition element and has a variable valence. Using a nickel salt, 2 F (faradays) plate out 39.2 g of nickel. What ions are in the solution of this salt?

Atomic molar mass: Ni (58.7 g mol ^-1)

(A) Ni^+

(B) Ni^2+

(C) Ni^3+

(D) Ni^2/3+

Answer 1

First, we'll determine the moles of Ni that were plated out.

39.2 g Ni x 1 mole Ni / 58.7 g = 0.6678 moles Ni

Next, we'll figure out how many moles of electrons were associated with this:

2 F x 1 mol e- / F = 2 moles of electrons.

Finally, we can determine the charge on the nickel:

2 moles electrons / 0.6678 moles Ni = 2.99 = 3 moles of electrons per mole Ni plated out.

ANSWER = (C) Ni³⁺

Ni³⁺(aq) + 3e- ==> Ni(s)