What is the boiling point of a solution of 0.150g of glycerol in 20g of water? What is the freezing point?
To find the boiling point and freezing point of a solution, we need to consider the colligative properties. These properties are dependent on the number of solute particles in a solution and not on the identity of the solute itself. In this case, glycerol is the solute.
The boiling point elevation and freezing point depression equations are given by:
ΔTb = kb * m
ΔTf = kf * m
Where:
- ΔTb is the boiling point elevation,
- ΔTf is the freezing point depression,
- kb is the molal boiling point elevation constant,
- kf is the molal freezing point depression constant, and
- m is the molality of the solution.
First, we need to calculate the molality (m) of the solution. Molality is the measure of the number of moles of solute per kilogram of solvent.
Step 1: Calculate the number of moles of glycerol (solute):
The molar mass of glycerol (C3H5(OH)3) is:
3(C) + 5(H) + 3(O) + 3(H) = 92 g/mol
The number of moles of glycerol can be calculated using the given mass:
m = mass / molar mass
m = 0.150 g / 92 g/mol
Step 2: Calculate the mass of water (solvent):
The mass of water is given as 20 g.
Step 3: Calculate the molality (m):
molality (m) = moles of solute / mass of solvent (in kg)
m = (0.150 g / 92 g/mol) / (20 g / 1000 g/kg)
Now that we have the molality (m), we can proceed to calculate the boiling point elevation (ΔTb) and freezing point depression (ΔTf).
Step 4: Calculate the boiling point elevation (ΔTb):
To find the boiling point elevation, we need to obtain the boiling point elevation constant (kb). The value of kb for water is approximately 0.512 °C/m.
ΔTb = kb * m
Step 5: Calculate the freezing point depression (ΔTf):
To find the freezing point depression, we need to obtain the freezing point depression constant (kf). The value of kf for water is approximately 1.86 °C/m.
ΔTf = kf * m
It is important to note that the boiling point elevation and freezing point depression are approximations and assume ideal behavior of the solute. In reality, there may be deviations from these values due to factors like molecular interactions.
By following these steps, you should be able to calculate the boiling point elevation and freezing point depression of the given solution of glycerol in water.