Some Basic Concepts of Chemistry - Result Question 19
####19. The number of moles of $KMnO _4$ that will be needed to react with one mole of sulphite ion in acidic solution is
(a) $\frac{2}{5}$
(b) $\frac{3}{5}$
(c) $\frac{4}{5}$
(d) 1
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Solution:
- Molarity $=\frac{\text { Moles of solute }}{\text { Volume of solution (L) }}$
Moles of urea $=\frac{120}{60}=2$
Weight of solution $=$ Weight of solvent + Weight of solute
$$ \begin{array}{rlrl} & =1000+120=1120 g \ \Rightarrow & \text { Volume } & =\frac{1120 g}{1.15 g / mL} \times \frac{1}{1000 mL / L}=0.973 L \ \Rightarrow & \text { Molarity } & =\frac{2.000}{0.973}=2.05 M \end{array} $$
