Question

What is the vapor pressure of an aqueous solution containing 10 %(by weight) ethylene glycol (62 g/mol) at 25 C. PH2O= 24.3 torr at 25 C.

Answer 1

Answer:

10% of the Ethylene glycol means we have to consider its weight = 10 g

Remaining 90% water means we have to consider the water weight = 90 g

molar mass of Ethylene glycol = 62 g/ mol
Number of moles = Weight / molar mass

Number of moles of ethylene glycol = 10/ 62 = 0.161

weight of water = 90 g
Number of moles of water = 90 / 18 = 5

mole fraction of water = (water moles) / (water moles + Ethylene glycol moles)

mole fraction of water = 5 / ( 5 + 0.161) =0.969

Vapour pressure = Total pressure x mole fraction

p = 24.3 x 0.969 = 23.5 torr.