Question

How many moles of electrons are required for reduction of 9 moles of Cr³⁺ to Cr?

Options

• 10 mol

• 15 mol

• 18 mol

• 27 mol

Answer 1

27 mol

Explanation:

The balanced equation for the reduction of Cr³⁺ to Cr is

\[\ce{Cr^{3+}_{( aq)} + 3e^- -> Cr_{(s)}}\]

The equation shows that 1 mole of Cr³⁺ is reduced to Cr by 3 moles of electrons.

For reduction of 9 moles of Cr³⁺, 3 × 9 = 27 moles of electrons will be required.