the freezing point of ethanol (C2H5OH) is -114.6C. the molal freezing point depression constant for ethanol is 2.00C/m. what is the freezing point (C) of a solution prepared by dissolving 50.0 g of glycerin (C3H8O3, A nonelectrolyte) in 200 g of ethanol.
any help would be appreciated im very confused.
thank you looks like i double posted... sorry
i tried to solve it on my own but im confused about the last part, this i what i have so far..
moles of glycerin= 50.0/92.10=0.54
molality=0.54/0.200=2.7
is that right?
im a little confused about the numbers im supposed to use for step 3...
To find the freezing point of the solution, we need to use the molal freezing point depression equation:
ΔTf = Kf * m
Where:
ΔTf is the change in freezing point
Kf is the molal freezing point depression constant
m is the molality of the solution
First, let's calculate the molality (m) of the solution:
Molality (m) = moles of solute / mass of solvent (in kg)
1. Calculate the moles of glycerin (C3H8O3):
The molar mass of glycerin (C3H8O3) is:
3(C) + 8(H) + 3(O) = 92 g/mol
Moles of glycerin = mass of glycerin / molar mass of glycerin
Moles of glycerin = 50.0 g / 92 g/mol
2. Calculate the mass of the solvent (ethanol) in kg:
Mass of solvent (ethanol) = 200 g
Mass of solvent (ethanol) = 200 g / 1000 (to convert to kg)
Now we have the moles of glycerin and the mass of ethanol in kg, we can calculate the molality (m):
Molality (m) = moles of glycerin / mass of ethanol (in kg)
Now that we have the molality, we can calculate the change in freezing point (ΔTf):
ΔTf = Kf * m
Finally, we can calculate the freezing point of the solution by subtracting the change in freezing point (ΔTf) from the freezing point of pure ethanol (-114.6°C).
Freezing point of solution = Freezing point of pure ethanol - ΔTf
Substitute the values into the equation, and you'll find the freezing point of the solution.
moles glycerin = grams/molar mass
solve for moles glycerin.
molality = mole/kg solvent
solve for molality
delta T = K*m
solve for delta T, then freezing point.