Calculate the freezing and boiling points of a solution containing 14.9g FeCl3 in 176g water.
calculate the moles of Ferric Chloride
molality=molesFeCl3/.176
freezing point= 0 - m*1.86
boiling point= 100+m*0.51
Note: Don't forget the van't Hoff factor of 4 for FeCl3.
To calculate the freezing and boiling points of a solution, we need to use the concept of colligative properties. The freezing point depression and boiling point elevation are examples of colligative properties, which depend on the number of solute particles present in the solution.
The freezing point depression can be calculated using the equation:
∆Tf = Kf * m
Where ∆Tf is the change in freezing point, Kf is the molal freezing point depression constant, and m is the molality of the solution (moles of solute per kilogram of solvent).
The boiling point elevation can be calculated using the equation:
∆Tb = Kb * m
Where ∆Tb is the change in boiling point, Kb is the molal boiling point elevation constant, and m is the molality of the solution (moles of solute per kilogram of solvent).
First, we need to calculate the molality of the solution using the given mass of solute (FeCl3) and solvent (water).
Step 1: Calculate the moles of FeCl3:
To find the moles of FeCl3, we need to divide the given mass by its molar mass. The molar mass of FeCl3 can be calculated by adding the molar mass of iron (Fe) to three times the molar mass of chlorine (Cl).
FeCl3: (1 * atomic mass of Fe) + (3 * atomic mass of Cl)
FeCl3: (1 * 55.84 g/mol) + (3 * 35.45 g/mol)
FeCl3: 162.2 g/mol
moles of FeCl3 = mass of FeCl3 / molar mass of FeCl3
moles of FeCl3 = 14.9 g / 162.2 g/mol
Step 2: Calculate the molality of the solution:
Molality (m) is defined as moles of solute per kilogram of solvent.
molality (m) = moles of solute / mass of solvent (in kg)
mass of solvent = mass of water = 176 g = 0.176 kg
molality (m) = moles of FeCl3 / mass of water
Now we can calculate the molality using the values from Step 1:
molality (m) = 14.9 g / (0.176 kg)
Next, we can calculate the freezing point depression (∆Tf) and boiling point elevation (∆Tb) using the molality and the appropriate constants.
The molal freezing point depression constant (Kf) for water is approximately 1.86 °C/m.
The molal boiling point elevation constant (Kb) for water is approximately 0.512 °C/m.
∆Tf = Kf * m
∆Tb = Kb * m
Finally, we can calculate the freezing point and boiling point of the solution.
Freezing point of the solution = Freezing point of pure water - ∆Tf
Boiling point of the solution = Boiling point of pure water + ∆Tb
Keep in mind that the freezing point depression and boiling point elevation calculations assume ideal behavior and do not take into account other factors that may affect the solution. The values obtained from these calculations are approximate and may differ slightly from actual experimental values.