1. Tardigrade
  2. Question
  3. Chemistry
  4. The total pressure observed by mixing two liquids A and B is 350 mm Hg when their mole fractions are 0.7 and 0.3 respectively. The total pressure becomes 410 mm Hg if the mole fractions are changed to 0.2 and 0.8 respectively for A and B. The vapour pressure of pure A is mm Hg. (Nearest integer) Consider the liquids and solutions behave ideally.

Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

Q. The total pressure observed by mixing two liquids $A$ and $B$ is $350 \, mm$ Hg when their mole fractions are $0.7$ and $0.3$ respectively.
The total pressure becomes $410 \,mm \,Hg$ if the mole fractions are changed to $0.2$ and $0.8$ respectively for $A$ and $B$. The vapour pressure of pure $A$ is _________$mm \,Hg$. (Nearest integer) Consider the liquids and solutions behave ideally.

JEE MainJEE Main 2023Solutions

Solution:

Let V.P. of pure $A$ be $P _{ A }^0$
Let V.P of pure $B$ be $P_B^0$
When $X _{ A }=0.7 \& X _{ B }=0.3$
$ P _{ s }=350$
$ \Rightarrow P _{ A }^0 \times 0.7+ P _{ B }^0 \times 0.3=350 ....$(i)
When $X _{ A }=0.2 \& X _{ B }=0.8$
$P _{ s }=410$
$ \Rightarrow P _{ A }^0 \times 0.2+ P _{ B }^0 \times 0.8=410,......$(ii)
Solving (i) and (ii)
$ P _{ A }^0=314 \,mm \,Hg $
$P _{ B }^0=434\, mm \,Hg $
$ =(314)$