Mass of flask = 81.39g
Mass of flask and water = 104.26g
Mass of flask ,water,and solute =129.53
Mass of solute= 25.27g
Boiling point of water =98.7C
Boiling point of solution =109.5C
Calculate the molecular weight of the solute using the data.
M=Kb*r solute/delta Tb*kg solvent
kb=0.512C/m
delta T = Kb*molality
Solve for molality.
molality = moles/kg solvent
Solve for moles
moles = grams/molar mass
solve for molar mass.
To calculate the molecular weight of the solute, we will use the equation:
M = (Kb * r_solute) / (ΔTb * kg_solvent)
Given information:
- Kb (molal boiling point elevation constant) = 0.512°C/m
- ΔTb (change in boiling point) = boiling point of solution - boiling point of water
- kg_solvent = mass of water in kg
- r_solute (van 't Hoff factor) = number of particles the solute dissociates into when dissolved
First, let's find the ΔTb:
ΔTb = boiling point of solution - boiling point of water
ΔTb = 109.5°C - 98.7°C
ΔTb = 10.8°C
Next, let's calculate the mass of water in kg:
mass of water = mass of flask and water - mass of flask
mass of water = 104.26g - 81.39g
mass of water = 22.87g
Since we need the mass in kg, divide by 1000:
kg_solvent = 22.87g / 1000
kg_solvent = 0.02287kg
Now, substitute the values into the equation:
M = (Kb * r_solute) / (ΔTb * kg_solvent)
M = (0.512°C/m * 1) / (10.8°C * 0.02287kg)
M = (0.512) / (0.247176)
M = 2.0732
Therefore, the molecular weight of the solute is approximately 2.0732 g/mol.