Answer:
the highest vapor pressure is the solution (b) P = 23.552 torr
∴ sln (a): P = 23.33 torr
∴ sln (c): P = 23.370 torr
Explanation:
vapor pressure:
- ΔP = - (P*a)(Xb,l) = P - P*a
∴ a: solvent (water)
∴ b: solute
assuming T=25°C:
∴ P*a (25°C) = 23.8 torr
molecular weight:
∴ Mw H2O = 18 g/mol
∴ Mw glucose: 180.156 g/mol
∴ Mw sucrose = 342.3 g/mol
∴ Mw potassium acetate = 98.15 g/mol
∴ mol H2O = (100 mL)(1 g/mL)(mol/18 g) = 5.55 mol H2O
a) moles glucose = (20.0 g)(mol/180.156 g) = 0.111 mol
⇒ Xb,l = (0.111 mol C6H12O6)/(5.55 + 0.111) = 0.0196
⇒ ΔP = - (23.8 torr)(0.0196) = - 0.466 torr = P - P*a
⇒ P = 23.8 torr - 0.466 torr = 23.33 torr
b) moles sucrose = (20 g)(mol/342.3 g) = 0.0584 mol
⇒Xb,l = (0.0584)/(5.55 + 0.0584) = 0.0104
⇒ ΔP = - (23.8 torr)(0.0104) = - 0.248 torr
⇒ P = 23.8 torr - 0.248 torr = 23.552 torr
c) moles KC2H3O2 = (10 g)(mol/98.15 g) = 0.102 mol
⇒ Xb,l = (0.102)/(5.55 + 0.102) = 0.0180
⇒ ΔP = - (23.8 torr)(0.0180) = - 0.429 torr
⇒ P = 23.8 torr - 0.429 torr = 23.370 torr
