Question

The molar ratio of $F{e}^{2+}$ to $F{e}^{3+}$ in a mixture of $FeS{O}_4$ and $F{e}_2{\left(S{O}_4\right)}_3$ having equal number of sulphate ions in both ferrous and ferric sulphates is

• A. 1:2
• B. 3:2
• C. 2:3
• D. none of these

Answer 1

Answer: (B)

$3FeS{O}_4\to 3F{e}^{2+}+3S{O}_4^{2-}$
$F{e}_2{\left(S{O}_4\right)}_3\to 2F{e}^{3+}+3S{O}_4^{2-}$
Suppose $x$ mole $S{O}_4^{2-}$ ions are furnished by both $FeS{O}_4$
and $F{e}_2{\left(S{O}_4\right)}_3$
Number of moles of $F{e}^{2+}=x$
Number of moles of $F{e}^{3+}=\frac{2}{3}x$
$\begin{array}{l}F{e}^{2+}:F{e}^{3+}=x:\frac{2}{3}x\\ =3:2\end{array}$