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Solutions

Question
CBSEENCH12005742

Vapour pressure of water at 293 K is 17.535 mm Hg. Calculate the vapour pressure of water at 293 K when 25 g of glucose is dissolved in 450 g of water.

Solution
Answer:
Vapour pressure of water pA0 = 17.535mm of Hg
Mass of glucose W2 = 25 g
mass of water w1 = 450g
we know that 
mass of glucose = 180gmol-1
molar mass of glucose =25/180g mol-1
mass of water = 18 g
molar mass of water M2 = 450/18 g mol-1
apply equation we get,

pA0-pApA0=xA


 17.535-pA17.535=25/180450/18


or      17.535-pA17.535 = 25180×18450=1180


or  180(17.535-pA) = 17.535

or  3156.30-180pA = 17.535

or                   3138.765 = 180pA

or                      pA = 3138.765180 = 17.44 mm Hg.