A voltaic cell is prepared in which aluminum metal is oxidized to Al³⁺, and nickel(II)is reduced to nickel metal. Which of the following represents the correctly balanced equation for this reaction?

Question

Quizplus · Accepted Answer

To balance the oxidation half-reaction, we need to add 6 electrons to the left side to balance the charge of 3 aluminum atoms becoming Al3+ ions. This gives the equation: 2Al(s) → 2Al3+(aq) + 6e-. 
To balance the reduction half-reaction, we need to have 6 electrons added to the right side to balance 3 Ni2+ ions becoming 3 Ni atoms. This gives the equation: 3Ni2+(aq) + 6e- → 3Ni(s). 
Multiplying the oxidation reaction by 3 and the reduction reaction by 2 gives us the following overall balanced equation: 
2Al(s) + 3Ni2+(aq) → 2Al3+(aq) + 3Ni(s) 
When written with the sulfide ions in the electrolyte, this equation becomes: 
2Al(s) + 3NiS + 6H2O → 2Al(OH)3 + 3Ni(s) + 3H2S. 
Therefore, the correct balanced equation is C.

A Voltaic Cell Is Prepared in Which Aluminum Metal Is