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CBSE Class 12 Chemistry 2023 Outside Delhi Set 1 Solved Paper

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Question : 19 of 35
Marks: +1, -0
SECTION - B
The vapour pressure of pure liquid XX and pure liquid YY at 25∘C25^{\circ}\mathrm{C} are 120 mm Hg120\,\text{mm}\,\text{Hg} and 160 mm Hg160\,\text{mm}\,\text{Hg} respectively. If equal moles of XX and YY are mixed to form an ideal solution, calculate the vapour pressure of the solution.
X=120 mm Hg,PA=PA0⋅xAX=120\,\text{mm}\,\text{Hg}, P_A=P_A^0 \cdot x_A
Y=160 mm Hg,PB=PB0⋅xBY=160\,\text{mm}\,\text{Hg}, P_B=P_B^0 \cdot x_B
∵\because When equal amount of XX and YY are mixedxA+xB=1x_A+x_B=1
Acc. to Raoutt's law
Ptotal=PA+PBP_{\text{total}}=P_A+P_B
PA0xA+PB0xBP_A^0 x_A + P_B^0 x_B
=(1−xB)PA0+xBPB0=(1-x_B)P_A^0+x_B P_B^0
PTotal=PA0+(PB0−PA0)xBP_{\text{Total}}=P_A^0+(P_B^0-P_A^0)x_B
=120+(160−120)×1=120+(160-120)\times 1
PTotal=120+40P_{\text{Total}}=120+40
=160 mm Hg=160\,\text{mm}\,\text{Hg}
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