To calculate the freezing point of a solution made by mixing 40 grams of a solute in chloroform, we need to apply the concept of freezing point depression.
The formula for freezing point depression is:
ΔTf = Kf * m
Where:
- ΔTf is the freezing point depression.
- Kf is the freezing point depression constant of the solvent (chloroform in this case), which is 4.70 °C/m.
- m is the molality of the solution.
First, we need to calculate the molality (m) of the solution. Molality is defined as the number of moles of solute per kilogram of solvent.
To find the moles of the solute, we need its molar mass. For this example, let’s assume the solute is a non-volatile, non-electrolyte solid. If we take the molar mass of the solute to be M g/mol, the calculation for moles would be:
moles of solute = 40 g / M g/mol
Next, we need the mass of the chloroform solvent. Since we know the density of chloroform is 1.483 g/cm³, we can determine the mass of a specific volume of chloroform. For instance, if we have 1000 grams of chloroform (or 1 L), the mass of the solvent in kilograms is:
mass of chloroform = 1000 g / 1000 = 1 kg
Now we can calculate molality:
m = (moles of solute) / (mass of solvent in kg)
Now plug the value of molality into the freezing point depression formula:
ΔTf = Kf * m = 4.70 °C/m * m
Finally, to find the new freezing point of the solution:
Freezing point of solution = Freezing point of pure chloroform – ΔTf
Freezing point of solution = 63.5 °C – ΔTf
The exact numerical answer will depend on the molar mass of the solute used. If the molar mass is known, you can determine the moles of solute, calculate molality, compute ΔTf and subsequently find the freezing point of the solution.