16.636 g of a non-volatile solute is dissolved in 410.0 g of water. The solute does not...

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Chemistry

16.636 g of a non-volatile solute is dissolved in 410.0 g ofwater.
The solute does not react with water nor dissociate insolution.
Assume that the resulting solution displays ideal Raoult's lawbehaviour.
At 90Â°C the vapour pressure of the solution is 517.01 torr.
The vapour pressure of pure water at 90Â°C is 525.80torr.Â Â The molar mass of the solute is 43.0g/mol.
Now suppose, instead, that 16.636 g of a volatilesolute is dissolved in 410.0 g of water.
This solute also does not react with water nor dissociate insolution.
The pure solute displays, at 90Â°C, a vapour pressure of 52.58torr.
Again, assume an ideal solution.
If, at 90Â°C the vapour pressure of this solution is also 517.01torr.
Calculate the molar mass of this volatilesolute.

Answer & Explanation Solved by verified expert

4.3 Ratings (732 Votes)

vapor pressure of solution = vapor pressure of water * molefraction

Â Â Â Â Â Â Â Â 517.01Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = 525.8* mole fraction

mole fraction of water = 517.01/525.8 = 0.983
no of moles of water = W/G.M.Wt = 410/18 = 22.8moles
mole fraction of water = no of moles of water/no of moles of water + no of moles of solute
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0.983Â Â Â Â Â Â Â Â Â Â Â Â = 22.8/22.8+x

Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 0.983*(22.8+x) = 22.8

Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â x = 0.394
no of moles of solute = 0.394 moles
molar mass of solute = 16.636/0.394Â Â = 42.22g/mole

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