# Science - Chemistry

posted by Sara

If vapour pressure of water is 17.5 torr at 20C, what is the water vapour pressure inside a bottle of 100 proof whiskey?

100 proof = 50% ethanol
Total volume = 1 L
Mass of ethanol = 394.5g
Mass of water = 500g
Density of ethanol = 0.789g/mL
Moles of ethanol = 8.58 mol
Moles of water = 27.75 mol
Molar concentration of ethanol = 17 molal

1. Andre

I am not sure. Can somebody please confirm

mol fraction of water : 27.75mol/36.3395mol = 0.76

mol fraction of ethanol : 8.5849 mol/36.3395 = 0.24

Vapour pressure of water inside a bottle of 100 proof : 13.3mmHg
(0.76)(17.5mmHg) = 13.3mmHg

Ptot = (0.76)(17.5mmHg) + (0.24)(44mmHg)
Ptot = 23.86mmHg

2. Merccedz

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