Question

Balance the following redox equation and determine how many electrons were transferred. `Zn(s) + Ni^(3+) (aq) → Zn^(2+) (aq) + Ni(s)`?

Answer 1

Consider,

`Zn(s) + Ni^(3+)(aq) to Zn^(2+)(aq) + Ni(s)`

and its resolution into components,

`Zn(s) to Zn^(2+) + 2e^-`
`Ni^(3+) + 3e^- to Ni(s)`

In order "balance" this reduction-oxidation equation, the electrons oxidized and used by the oxidizing agent must be equal. Hence,

`3Zn(s) to 3Zn^(2+) + 6e^-`
`2Ni^(3+) + 6e^(-) to 2Ni(s)`

is equivalent to,

`3Zn(s) + 2Ni^(3+)(aq) to 3Zn^(2+)(aq) + 2Ni(s)`

Always think of the electrons. Always!