Answer:
110.9 g/mol is the molar mass of the solute
Explanation:
ΔT = Kf . m → Colligative property of freezing point depression
7.30°C = 3.91 °C/m . m
Kf is the cryoscopic constant for the solvent
m is molality (moles of solute in 1kg of solvent)
7.30°C / 3.91m/°C = m → 1.87 mol/kg
This moles of the solute are in 1kg of solvent, but our mass of solvent is 28 g. We convert the mass of solvent from g to kg
28 g . 1kg / 1000g = 0.028 kg
We find out the moles → 1.87 mol/kg . 0.028kg = 0.0523 moles
This moles are the amount of 5.80 g. We can determine the molar mass:
g/mol = 5.80 g /0.0523 mol = 110.9 g/mol
Answer:
The molar mass of the solute is 110.9 g/mol
Explanation:
Step 1: Data given
Mass of a nonelectrolyte = 5.80 grams
Mass of solvent = 28.0 grams
freezing point depression ∆T = 7.30 °C
Freezing point depression constant = 3.91 °C /m
Step 2: Calculate molality
∆T = i*Kf * m
⇒∆T = the freezing point depression = 7.30 °C
⇒i = the van't Hoff factor = 1
⇒Kf = the freezing point depression constant = 3.91 °C/m
⇒m = molality = moles solute / mass solvent
m = 7.30 /3.91
m = 1.867 molal
Step 3: Calculate moles solute
Moles solute = molality * mass of solvent
Moles solute = 1.867 molal * 0.028 kg
Moles solute = 0.0523 moles
Step 4: Calculate molar mass
Molar mass = mass / moles
Molar mass = 5.80 grams / 0.0523 moles
Molar mass = 110. 9 g/mol
The molar mass of the solute is 110.9 g/mol
