Question

The vapor pressure of water at 65oC is 187.54 mmHg. What is the vapor pressure of a ethylene glycol (CH2(OH)CH2(OH)) solution made by dissolving 22.37 g of ethylene glycol in 82.21 g of water?

Answer 1

173.83 mmHg is the vapor pressure of a ethylene glycol solution.

Step-by-step explanation:

Vapor pressure of water at 65 °C=
`p_o= 187.54 mmHg`

Vapor pressure of the solution at 65 °C=
`p_s`

The relative lowering of vapor pressure of solution in which non volatile solute is dissolved is equal to mole fraction of solute in the solution.

Mass of ethylene glycol = 22.37 g

Mass of water in a solution = 82.21 g

Moles of water=
`n_1=(82.21 g)/(18 g/mol)=4.5672 mol`

Moles of ethylene glycol=
`n_2=(22.37 g)/(62.07 g/mol)=0.3603 mol`

`(p_o-p_s)/(p_o)=(n_2)/(n_1+n_2)`

`(187.54 mmHg-p_s)/(187.54 mmHg)=(0.3603 mol)/(0.3603 mol+4.5672 mol)`

`p_s=173.83 mmHg`

173.83 mmHg is the vapor pressure of a ethylene glycol solution.