Question

$3$ Faradays of electricity was passed through an aqueous solution of iron $\left(II\right)$ bromide. The weight (in g) of iron metal (atomic weight $=56$ amu) deposited at the cathode is:

• A. $56$
• B. $84$
• C. $112$
• D. $168$

Answer 1

Answer: (B)

$84$

$3$ Faradays of electricity was passed through an aqueous solution of iron (II) bromide.

$3$ F of electricity $\equiv 3$ moles of electrons

$F{e}^{2+}+2e^{-}\to Fe$

$2$ moles of electrons gives $1$ mole of $Fe$

$3$ moles of electrons gives $=\frac{3}{2}$ moles of $Fe$

$=\frac{3}{2}\times 56$ $=84$ g

Hence, $84$ g of iron metal is deposited at the cathode.