Respuesta :
Answer: 21.7 torr
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,
[tex]\frac{p^o-p_s}{p^o}=i\times x_2[/tex]
where,
[tex]\frac{p^o-p_s}{p^o}[/tex]= relative lowering in vapor pressure
i = Van'T Hoff factor = 1 (for non electrolytes)
[tex]x_2[/tex] = mole fraction of solute =[tex]\frac{\text {moles of solute}}{\text {total moles}}[/tex]
Given : 32.7 g of glycerol is present in 100 g of aqueous solution, thus (100-32.7) g = 67.3 g of water
moles of solute (glycerol) = [tex]\frac{\text{Given mass}}{\text {Molar mass}}=\frac{32.7g}{92.1g/mol}=0.355moles[/tex]
moles of solvent (water) = [tex]\frac{\text{Given mass}}{\text {Molar mass}}=\frac{67.3g}{18g/mol}=3.74moles[/tex]
Total moles = moles of solute (glycerol) + moles of solvent (water) = 0.355 + 3.74 = 4.095
[tex]x_2[/tex] = mole fraction of solute =[tex]\frac{0.355}{4.095}=0.0867[/tex]
[tex]\frac{23.8-p_s}{23.8}=1\times 0.0867[/tex]
[tex]p_s=21.7torr[/tex]
Thus the vapor pressure of the solution at [tex]25^0C[/tex] is 21.7 torr
