Answer:
Vapor pressure of solution is 98.01 Torr
Explanation:
Colligative property. In this case, we apply the lowering vapor pressure.
ΔP = P° . Xm
P° - P' = Vapor pressure of pure solvent - Vapor pressure of solution = ΔP
Xm is the molar fraction for solute. We try to determine it:
Moles of solute / Total moles → Total moles = Solute moles + Solvent moles
10.3 g . 1mol / 154 g = 0.0669 moles of biphenyl
27.8 g . 1mol / 78 g = 2.32 moles of benzene
Total moles = 2.32 moles + 0.0669 moles = 2.3869 moles
Xm for solute = 0.0669 / 2.3869 = 0.028
Let's replace data:
100.84 Torr - P' = 100.84 Torr . 0.028
P' = - (100.84 Torr . 0.028 - 100.84Torr) = 98.01 Torr
Answer:
The vapor pressure of the solution is 84.9 torr
Explanation:
Biphenyl is a nonvolatile, nonionizing solute
Temperature = 25.0 °C
Vapor pressure = 100.84 torr
Mass of biphenyl = 10.3 grams
Mass of benzene = 27.8 grams
Molar mass biphenyl = 154.21 g/mol
Molar mass benzene = 78.11 g/mol
Step 2: Calculate moles
Moles = mass / molar mass
Moles biphenyl = 10.3 grams / 154.21 g/mol
Moles biphenyl = 0.0668 moles
Moles benzene = 27.8 grams / 78.11 g/mol
Moles benzene = 0.356 moles
Step 3: Calculate total moles
Total moles = 0.0668 moles + 0.356 moles
Total moles= 0.4228 moles
Step 4: Calculate mol fraction benzene
Mol fraction benzene = moles benzene / total moles
Mol fraction benzene = 0.356 moles / 0.4228 moles
Mol fraction benzene = 0.842
Step 5: Calculate vapor pressure of the solution
Psol = Xbenzene * P°benzene
⇒Psol = the vapor pressure of the solution
⇒Xbenzene = mol fraction of benzene
⇒P°benzene = the vapor pressure of pure benzene
Psol = 0.842 * 100.84 torr
Psol = 84.9 torr
The vapor pressure of the solution is 84.9 torr
