Solutions and Colligative Properties 2 Question 20
20. $0.004 \mathrm{M} \mathrm{Na}{2} \mathrm{SO}{4}$ is isotonic with $0.01 \mathrm{M}$ glucose. Degree of dissociation of $\mathrm{Na}{2} \mathrm{SO}{4}$ is
$(2004$, S, 1M)
(a) $75 %$
(b) $50 %$
(c) $25 %$
(d) $85 %$
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Solution:
- For isotonic solutions, they must have same concentrations of ions, Therefore,
$$ \begin{aligned} & 0.004 i\left(\mathrm{Na}{2} \mathrm{SO}{4}\right)=0.01 \ & \Rightarrow \quad i=\frac{0.01}{0.004}=2.5 \end{aligned} $$
$$ \begin{aligned} & \Rightarrow \quad i=1+2 \alpha=2.5 \ & \alpha=0.75=75 % \end{aligned} $$
