Respuesta :
Explanation:
Since, NaCl exists as [tex]Na^{+}[/tex] and [tex]Cl^{-}[/tex] in solution. Therefore, Van't Hoff factor (i) will be equal to 2.
Now, we assume that there are "n" moles of NaCl in the given solution. And, we assume that there is 1 kg of solvent (water).
So, [tex]\frac{\Delta P}{P} = i \times \frac{\text{no. of moles of NaCl}}{\text{Mass of water in kg}}[/tex]
[tex]\frac{23.8 torr - 17.5 torr}{23.8 torr} = 2 \times \frac{n}{1}[/tex]
0.264 = [tex]2 \times \frac{n}{1}[/tex]
n = 0.132
Also, moles of water will be calculated as follows.
Moles of water = [tex]\frac{1000}{18}[/tex]
= 55.56 mol
Hence, mole fraction of NaCl is calculated as follows.
Mole fraction = [tex]\frac{0.132}{55.56 + 0.132}[/tex]
= [tex]2.37 \times 10^{-3}[/tex]
Hence, mole fraction of NaCl will be [tex]2.37 \times 10^{-3}[/tex].
At [tex]45^{o}C[/tex], the vapor pressure will be calculated as follows.
[tex]\frac{71.9 - p}{71.9} = 2 \times \frac{n}{\text{mass of water in kg}}[/tex]
[tex]\frac{71.9 - p}{71.9} = 2 \times \frac{0.132}{1}[/tex]
71.9 - p = 18.98
p = 52.92 torr
Therefore, vapor pressure of the given solution is 52.92 torr.
