Question

The molar ratio of $Fe^{2 +}$ to $Fe^{3 +}$ in a mixture of $FeSO_{4}$ and $Fe _2\left( SO _4\right)_3$ 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)

$3 FeSO _4 \rightarrow 3 Fe ^{2+}+3 SO _4^{2-}$
$Fe _2\left( SO _4\right)_3 \rightarrow 2 Fe ^{3+}+3 SO _4^{2-}$
Suppose $x$ mole $SO _4^{2-}$ ions are furnished by both $FeSO _4$
and $Fe _2\left( SO _4\right)_3$
Number of moles of $Fe ^{2+}= x$
Number of moles of $Fe ^{3+}=\frac{2}{3} x$
$ \begin{array}{l} Fe ^{2+}: Fe ^{3+}= x : \frac{2}{3} x \\ =3: 2 \end{array} $