What is the vapor pressure of a solution (13 g of ethanol, 7 g of water, and 5 g

Question

What is the vapor pressure of a solution (13 g of ethanol, 7 g of water, and 5 g of sugar) at 60 degrees C if the vapor pressure of pure ethanol is 200 tore and the vapor pressure of water is 80 torr at this temperature? What is the vapor pressure of a solution (13 g of ethanol, 7 g of water, and 5 g of sugar) at 60 degrees C if the vapor pressure of pure ethanol is 200 tore and the vapor pressure of water is 80 torr at this temperature? What is the vapor pressure of a solution (13 g of ethanol, 7 g of water, and 5 g of sugar) at 60 degrees C if the vapor pressure of pure ethanol is 200 tore and the vapor pressure of water is 80 torr at this temperature?

Explanation / Answer

Molar mass of sugar = 342; Water =18; Ethanol =46

Moles of sugar = 5/342 = 0.0146

Moles of water = 7/18 = 0.3889

Moles of ethanol = 13/46

molefraction of ethanol = 0.4119

molefraction of water = 0.5668

Now partial pressure = pure vapour pressure*molefraction

Partial pressure of ethanol = 0.4119 * 200 torr = 82.38 torr

Partial pressure of water = 0.5668 * 80 torr = 45.34 torr

Sugar being in solid state do not exert vapour pressure.

So total pressure = 82.38+45.34 = 127.72 torr

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