freezing point and boiling point of 12g or glucose in 50g of water
moles glucose = grams/molar mass
molality = moles/kg solvent
Then delta T = Kf*molality or
delta T = Kb*molality
To determine the freezing point and boiling point of a solution, you need to know the molality (mol/kg) of the solute (glucose) in the solvent (water). With the given information (12g glucose and 50g water), we can calculate the molality and use it to find the freezing point depression and boiling point elevation constants.
1. Calculate the number of moles of glucose:
- We know the molar mass of glucose (C6H12O6) is approximately 180.16 g/mol.
- So, the number of moles of glucose is: 12g / 180.16 g/mol = 0.0666 mol.
2. Calculate the molality of the solution:
- Molality (m) is defined as the moles of solute per kilogram of solvent.
- The mass of water is 50g, which is equivalent to 0.05 kg.
- Molality (m) = moles of solute / mass of solvent (in kg).
- Molality (m) = 0.0666 mol / 0.05 kg = 1.332 mol/kg.
3. Use the molality to find the freezing point depression constant (Kf) and boiling point elevation constant (Kb). These constants depend on the solvent and are usually provided in a reference table. However, for water, the values commonly used are:
- Kf (freezing point depression constant of water) = 1.86 °C/m
- Kb (boiling point elevation constant of water) = 0.51 °C/m.
4. Calculate the freezing point depression:
- Freezing point depression (ΔTf) is given by the equation:
ΔTf = Kf × m
- ΔTf = 1.86 °C/m × 1.332 mol/kg = 2.47352 °C.
5. Calculate the boiling point elevation:
- Boiling point elevation (ΔTb) is calculated using the equation:
ΔTb = Kb × m
- ΔTb = 0.51 °C/m × 1.332 mol/kg = 0.67932 °C.
6. Finally, use the freezing point depression and boiling point elevation values to determine the freezing and boiling points of the solution.
- Freezing point = freezing point of water - ΔTf
- Boiling point = boiling point of water + ΔTb.
The freezing point and boiling point of the glucose solution can now be determined by subtracting the calculated freezing point depression from the freezing point of water and adding the calculated boiling point elevation to the boiling point of water.