Question

A solution is prepared containing a $2: 1$ mol ratio of dibromoethane $\left( C _{2} H _{4} Br _{2}\right)$ and dibromopropane $\left( C _{3} H _{6} Br _{2}\right)$. What is total vapor pressure of the solution assuming ideal behaviour?

• A. $300\, mm\, Hg$
• B. $142 \, mm \, Hg$
• C. $150 \, mm \, Hg$
• D. $158\, mm\, Hg$

Answer 1

Answer: (D)

$p=p_{A}+p_{B}=p_{A}^{\circ} x_{A}+p_{B}^{\circ} x_{B}$
$=173 \times \frac{2}{3}+127 \times \frac{1}{3}$
$=\frac{346+127}{3}=\frac{473}{3}$
$=157.6 \approx 158 \,mm$