Question

At 363 K , the vapour pressure of A is $21kPa$ and that of b is $18kPa$. 1 mol of A and 2 moles of B are mixed . Assuming that this solution is ideal , the vapour pressure of the mixture in $kPa$ rounded off to the Nearest Integer is

• A. 19.00
• B. 19.0
• C. 19

Answer 1

Answer: (A), (B), (C)

An ideal solution is prepared by mixing 1 mol of A and 2 moles of B

Using Raoult's law
$P_t$ is total pressure of solution
${\chi }_A,{\chi }_B$ are mole fractions of A and B in liquid phase
$P_A^0,P_B^0$ are vapour pressures of A and B in pure state

$P_t={\chi }_A{P}_A^0+{\chi }_B{P}_B^0$

$P_t=\frac{1}{3}\times 21+\frac{2}{3}\times 18=19kPa$