Question

The below reaction is the gold-plating process reaction.
${Au}^{3+}\left(aq\right)+3e^{-}\to Au\left(s\right)$
If $0.600g$ of $Au$ is plated onto a metal, how many coulombs are used?

• A. $299C$
• B. $868C$
• C. $2,990C$
• D. $8,680C$

Answer 1

Answer: (B)

$868C$

$A{u}^{3+}+3e^{-}\to Au\left(s\right)$
1 mole of $A{u}^{3+}$ requires 3 mol of electrons for reduction to $Au\left(s\right)$.
Moles of $Au$ in 0.600 g = $\frac{0.600}{197}=0.003$
1 mol of $A{u}^{3+}$ requires 3 mol , so 0.003 mol of $A{u}^{3+}$ requires$=3\times 0.003=0.009$ moles of electrons.
1 mol of electron has = 96500 C charge
0.009 moles of electrons has = $96500\times 0.009=868C$