Considering the redox reaction Cr + Ni²⁺ → Cr³⁺ + Ni, how many electrons are transferred in the balanced reaction?

The correct answer is : 6 electrons

Explanation:

From the reduction-oxidation reaction, we identify the half-reactions:

Oxidation reaction: Cr (oxidation number= 0)  loses 3 electrons and forms the cation Cr³⁺.

Cr → Cr³⁺ + 3 e-

Reduction reaction: the cation Ni²⁺ gains 2 electrons to form Ni (oxidation number= 0).

Ni²⁺ + 2 e- → Ni

We write the two half-reactions together and we multiply the reduction reaction by 3 and the oxidation reaction by 2 to obtain the same quantity of electrons in each half-reaction: 6.

(Ni²⁺ + 2 e- → Ni) x 3

(Cr → Cr³⁺ + 3 e-) x 2

3 Ni²⁺ + 2 Cr → 3 Ni + 2 Cr³⁺ (balanced reaction)

Therefore, in the balanced reaction a total of 6 electrons are transferred.