Solutions and Colligative Properties - Result Question 51
####22. The vapour pressure of pure benzene at a certain temperature is $640 mm Hg$. A non-volatile, non-electrolyte solid weighing $2.175 g$ is added to $39.0 g$ of benzene. The vapour pressure of the solution is $600 mm Hg$. What is the molecular weight of the solid substance?
(1990, 3M)
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Solution:
22.5=20 \chi _A+70\left(1-\chi _A\right) & \left(\text { As } \chi _A+\chi _B=1\right) \
