Answer:
The compound has a molar mass of 78.4 g/mol
Explanation:
Step 1: data given
Mass of a sample = 0.5 grams
Mass of benzene = 25 grams
Freezing poing = 5 °C
Kf of benzene = 5.1 °C/m
Freezing point solution = 3.7 °C
Step 2: Calculate molality
ΔT = i*Kf*m
⇒with ΔT = the freezing point depression = 5.0 - 3.7 = 1.3 °C
⇒with i = the can't hoff factor = 1
⇒with Kf = the freezing point depression constant of benzene = 5.1 °C/m
⇒with m = the molality
1.3 = 5.1 * m
m = 1.3 / 5.1
m = 0.255 moles /kg
Step 3: Calculate moles
Molality = moles / mass benzene
0.255 molal = moles / 0.025 kg
Moles = 0.255 molal * 0.025 kg
Moles = 0.006375 moles
Step 4: Calculate molar mass of the compound
Molar mass compund = mass / moles
Molar mass compound = 0.5 grams / 0.006375 moles
Molar mass compound = 78.4 g/mol
The compound has a molar mass of 78.4 g/mol
