Question

The vapor pressure of diethyl ether (ether) is 463.57 mm Hg at 25 °C. A nonvolatile, nonelectrolyte that dissolves in diethyl ether is chlorophyll. Calculate the vapor pressure of the solution at 25 °C when 11.79 grams of chlorophyll, C55H72MgN4O5 (893.5 g/mol), are dissolved in 153.2 grams of diethyl ether. diethyl ether = CH3CH2OCH2CH3 = 74.12 g/mol. VP(solution) = mm Hg

Answer 1

Answer: The vapor pressure of the solution at
`25^0C` is 460.63 mmHg

Step-by-step explanation:

As the relative lowering of vapor pressure is directly proportional to the amount of dissolved solute.

The formula for relative lowering of vapor pressure will be,

`(p^o-p_s)/(p^o)=i* x_2`

where,

`(p^o-p_s)/(p^o)`= relative lowering in vapor pressure

i = Van'T Hoff factor = 1 (for non electrolytes)

`x_2` = mole fraction of solute =
`\frac{\text {moles of solute}}{\text {total moles}}`

Given : 11.79 g of chlorophyll is present in 153.2 g of diethyl ether

moles of solute (chlorophyll) =
`\frac{\text{Given mass}}{\text {Molar mass}}=(11.79g)/(893.5g/mol)=0.01319moles`

moles of solvent (diethyl ether) =
`\frac{\text{Given mass}}{\text {Molar mass}}=(153.2g)/(74.12g/mol)=2.067moles`

Total moles = moles of solute + moles of solvent =0.01319 + 2.067 = 2.080

`x_2` = mole fraction of solute =
`(0.01319)/(2.080)=6.341* 10^(-3)`

`(463.57-p_s)/(463.57)=1* 6.341* 10^(-3)`

`p_s=460.63mmHg`

Thus the vapor pressure of the solution at
`25^0C` is 460.63 mmHg