Consider two solutions, one formed by adding 10 gof glucose (C6H12O6) to 1 L of

Question

Consider two solutions, one formed by adding 10 gof glucose (C6H12O6) to 1 L of water and the other formed by adding 10 g of sucrose (C12H22O11) to 1 L of water.

1)Calculate the vapor pressure for the first solution at 20 ?C. (The vapor pressure of pure water at this temperature is 17.5 torr.)

Express your answer using three significant figures.

2)Calculate the vapor pressure for the second solution at 20 ?C. (The vapor pressure of pure water at this temperature is 17.5 torr.)

Express your answer using three significant figures.

Explanation / Answer

vapor pressure drop is a colligative property, that is it depends on number of molecules, not their nature

10g of sucrose contains almost twice fewer molecules than 10 g of glucose, so pressure drop created by sucrose is smaller, and vapor pressure of its solution will be consequently higher

1.

16.4 % by mass means 16.4 g of ethylene glycol in 100 g of solution

mass water = 100 - 16.4 = 83.6 g
moles water = 83.6 g / 18.02 g/mol=4.63

moles ethylene glycol = 16.4 g / 62.07 g/mol=0.264

mole fraction water = 4.63 / 4.63 + 0.264 =0.946

p = p

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