Calculate the freezing point of a solution containing 12.2grams of benzoic acid, C6H5CO2H, dissolved in 250 grams of nitrobenzene, C6H5NO2. The freezing point of nitrobenzene is 7.7 C, and its freezing point depression constant is 7.0 C/m.
delta T = Kf*molality
Remember molality = #mols/kg solvent.
After you find delta T, then subtract that from 7.7 to find the freezing point of the solution.
where you got the 7.7 from? and how you calculate the molality for it. I am stuck please help
To calculate the freezing point of the solution, we need to use the formula:
ΔT = Kf * m
Where:
ΔT is the freezing point depression,
Kf is the freezing point depression constant, and
m is the molality of the solution.
First, we need to calculate the molality (m):
m = moles of solute / mass of solvent (in kg)
1. Convert the mass of benzoic acid from grams to moles:
To do this, we divide the mass (12.2 g) by the molar mass of benzoic acid.
The molar mass of benzoic acid (C6H5CO2H) = (6*12.01 + 6*1.01 + 2*16.00 + 1*1.01) g/mol
= 122.12 g/mol
Moles of benzoic acid = 12.2 g / 122.12 g/mol
2. Convert the mass of nitrobenzene from grams to kilograms:
The mass of nitrobenzene is already given in grams (250 g). We need to convert it to kilograms.
Mass of nitrobenzene = 250 g / 1000 (to convert grams to kg)
3. Calculate the molality (m):
m = moles of solute / mass of solvent (in kg)
Since we have already calculated the moles of benzoic acid and the mass of nitrobenzene in kilograms, we can substitute those values into the formula.
m = (moles of benzoic acid) / (mass of nitrobenzene)
4. Calculate the freezing point depression (ΔT):
We know the freezing point depression constant (Kf) is 7.0 C/m.
ΔT = Kf * m
Substitute the values from the calculations into the formula to find the freezing point depression.
5. Calculate the freezing point of the solution:
The freezing point depression is the difference between the freezing point of the pure solvent and the freezing point of the solution. Add the freezing point depression to the freezing point of the pure solvent.
Freezing point of solution = Freezing point of solvent - ΔT
The freezing point of the nitrobenzene solvent is given as 7.7 C.
Putting it all together, you can follow these steps to calculate the freezing point of the solution.