Verified Solution • 2025–26 Session moderate

QJEEM21Che019: JEE Main 2021 Chemistry - Class 12 JEEM21Che019 Solution: At 363 K, the vapour pressure of A is 21 kPa and that of B is…

At 363 K, the vapour pressure of A is 21 kPa and that of B is 18 kPa. One mole of A and 2 moles of B are mixed. Assuming that this solution is ideal, the vapour pressure of the mixture is ___________ kPa. (Round off to the Nearest Integer).

Step-by-Step Verified Solution

XA=11+2=13{X_A} = {1 \over {1 + 2}} = {1 \over 3}

XB=23{X_B} = {2 \over 3}

PAo=21kPaP_A^o = 21kPa

PBo=18kPaP_B^o = 18kPa

Ptotal=PAoXA+PBoXB{P_{total}} = P_A^o{X_A} + P_B^o{X_B}

=21×13+18×23= 21 \times {1 \over 3} + 18 \times {2 \over 3}

=7+12= 7 + 12

=19kPa= 19 kPa

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