Answer:
The molar mass of the solid is 511.3 g/mol
Explanation:
Step 1: Data given
Mass of the sample = 0.588 grams
Mass of benzene = 11.5 grams
The solution freezes at 5.02 °C
The freezing point of benzene is 5.51 °C
The freezing point depression constant, kf = 4.90 °C/m
Step 2: Determine the temperature change
Δt = 5.51 - 5.02 = 0.49°C
Step 3: Determine number of moles
Δt = i*Kf*m
⇒ with i = the number of dissolved particles the solute produces = 1
⇒ with Kf = the molal freezing point depression constant Kf = 4.90 °C*Kg/mol
⇒ with m = the molality of the solute
0.49 °C = (1) (4.90 °C kg/mol) (x / 0.01150 kg)
x = 0.00115 mol
Step 4: Calculate molar mass
0.588 grams / 0.00115 mol = 511.3 g/mol
The molar mass of the solid is 511.3 g/mol
