Solutions Question 118

Question: The vapour pressure lowering caused by the addition of 100 g of sucrose(molecular mass = 342) to 1000 g of water if the vapour pressure of pure water at 25oC is 23.8 mm Hg [RPET 1999]

Options:

A) 1.25 mm Hg

B) 0.125 mm Hg

C) 1.15 mm Hg

D) 00.12 mm Hg

Show Answer

Answer:

Correct Answer: B

Solution:

Given molecular mass of sucrose = 342 Moles of sucrose =100342=0.292 mole Moles of water N=100018=55.5 moles and Vapour pressure of pure water P0=23.8 mm Hg According to Raoul’s law ΔPP0=nn+NΔP23.8=0.2920.292+55.5

ΔP=23.8×0.29255.792=0.125 mm Hg.



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