Solutions and Colligative Properties - Result Question 26
26. Two liquids $A$ and $B$ form ideal solution. At $300$ K , the vapour pressure of a solution containing $1$ mole of $A$ and 3 moles of $B$ is $550$ mm of Hg . At the same temperature, if one more mole of $B$ is added to this solution, the vapour pressure of the solution increases by $10$ mm of Hg . Determine the vapour pressure of $A$ and $B$ in their pure states.
(1982,4M)
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Solution:
When $1.0$ mole of $A$ is mixed with $3$ moles of $B$.
$ 550=0.25 p_A^{\circ}+0.75 p_B^{\circ} \quad$ ……(i)
When $1.0$ mole of $A$ is mixed with $4$ moles of $B$.
$ 560=0.20 p_A^{\circ}+0.80 p_B^{\circ} \quad$……(ii)
Now, solving (i) and (ii)
$p_A^{\circ}=400 \mathrm{~mm}$
$ p_B^{\circ}=600 \mathrm{~mm} \text {. } $
BETA
