the freezing point of water is -1.86 degree Cm, if 5.00 g Na2SO4 is desolve at 45.0g H2o the freezing point is changed by -3.82 degree C. Calculate the Van't Hoff Factor for Na2SO4
I think you meant to say the freezing point depression constant is -1.86 degree C/m for water. (The normal freezing point is 0.00 C)
mols Na2SO4 = grams/molar mass = approx 0.035 but you need to do it more accurately.
molality = mol/kg solution = approx 0.035/0.045 = approx 0.8
delta T = i*Kf*m
3.82 = i*1.86*0.8
Solve for i.
To calculate the Van't Hoff Factor (i), we first need to determine the moles of Na2SO4 and H2O.
1. Calculate the moles of Na2SO4:
To do this, we need to know the molar mass of Na2SO4, which is 142.04 g/mol.
Moles of Na2SO4 = mass / molar mass
Moles of Na2SO4 = 5.00 g / 142.04 g/mol
2. Calculate the moles of H2O:
To do this, we need to know the molar mass of H2O, which is 18.02 g/mol.
Moles of H2O = mass / molar mass
Moles of H2O = 45.0 g / 18.02 g/mol
Now, we can calculate the Van't Hoff factor (i) using the following equation:
ΔTf = i * Kf * molality
Where:
ΔTf is the change in freezing point (in °C)
Kf is the cryoscopic constant for the solvent (water), which is -1.86 °C•kg/mol
molality is the moles of solute (Na2SO4) per kilogram of solvent (H2O)
3. Calculate the molality (m):
Molality (m) = moles of solute / mass of solvent (in kg)
Molality (m) = moles of Na2SO4 / mass of H2O (in kg)
4. Plug the values we have into the equation:
-3.82 °C = i * (-1.86 °C•kg/mol) * molality
Solve for i:
i = -3.82 °C / (-1.86 °C•kg/mol * molality)
Now, substitute the corresponding values and calculate i to find the Van't Hoff factor for Na2SO4.