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. $(p_1^o-p_2^o)x_1+p_2^o$
• B. $(p_2^o-p_1^o)x_1+p_2^o$
• C. $(p_1^o-p_2^o)x_1+p_1^o$
• D. $(p_2^o-p_1^o)x_1+p_1^o$

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

$\because$ $[x_1+x_2=1]$

$p=(p_1^o-p_2^o)x_1+p_2^o$