Question

A binary solution contains $x_{1}$ and $x_{2}$ mole fraction of two components having vapour pressure $p_{1}^{o}$ and $p_{2}^{o}$ in their pure states. The total vapour pressure above the solution is

• A. $\left(\right.p_{1}^{o}-p_{2}^{o}\left.\right)x_{1}+p_{2}^{o}$
• B. $\left(\right.p_{2}^{o}-p_{1}^{o}\left.\right)x_{1}+p_{2}^{o}$
• C. $\left(\right.p_{1}^{o}-p_{2}^{o}\left.\right)x_{1}+p_{1}^{o}$
• D. $\left(\right.p_{2}^{o}-p_{1}^{o}\left.\right)x_{1}+p_{1}^{o}$

Answer 1

Answer: (A)

According to Raoult's law, we have

$p_{1}=p_{1}^{o}x_{1}$ and $p_{2}=p_{2}^{o}x_{2}$

So $\mathrm{p}=\mathrm{p}_1+\mathrm{p}_2=\mathrm{p}_1^{\mathrm{o}} \mathrm{x}_1+\mathrm{p}_2^{\mathrm{o}}\left(1-\mathrm{x}_1\right)$

$\because $ $\left[\right.x_{1}+x_{2}=1\left]\right.$

$p=\left(\right.p_{1}^{o}-p_{2}^{o}\left.\right)x_{1}+p_{2}^{o}$