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.
freezing point depression=k*molesglycering/kg ethanol
New freezing point= original-depression
Lisa, I worked this problem for you last night, step by step.
Thank you for the help, i really appreciate it.
To find the freezing point of the solution, we can use the formula:
ΔTf = Kf * molality
Where:
ΔTf = freezing point depression (difference between the freezing point of the pure solvent and the solution)
Kf = molal freezing point depression constant for the solvent
molality = moles of solute / mass of solvent (in kg)
First, we need to calculate the molality of the solution:
Step 1: Convert the mass of glycerin to moles.
The molar mass of glycerin (C3H8O3) can be calculated as follows:
(3 * atomic mass of carbon) + (8 * atomic mass of hydrogen) + (3 * atomic mass of oxygen)
Molar mass of C3H8O3 = (3 * 12.01 g/mol) + (8 * 1.01 g/mol) + (3 * 16.00 g/mol)
Next, divide the given mass of glycerin by the molar mass you just calculated:
moles of glycerin = mass of glycerin / molar mass of glycerin
Step 2: Convert the mass of ethanol to kg.
The given mass of ethanol is in grams, so we need to convert it to kilograms:
mass of ethanol = 200 g / 1000 = 0.2 kg
Step 3: Calculate the molality.
Now we can calculate the molality using the moles of glycerin and the mass of ethanol:
molality = moles of glycerin / mass of ethanol (in kg)
Step 4: Calculate the freezing point depression (ΔTf).
We can now use the molal freezing point depression constant (Kf) for ethanol, which is given as 2.00°C/m, and the calculated molality to find the freezing point depression:
ΔTf = Kf * molality
Step 5: Calculate the freezing point of the solution.
Finally, we subtract the freezing point depression from the freezing point of the pure solvent (ethanol) to find the freezing point of the solution:
freezing point of solution = freezing point of pure solvent - ΔTf
Since we know the freezing point of ethanol is -114.6°C, we substitute this value into the equation:
freezing point of solution = -114.6°C - ΔTf
To find the final freezing point of the solution, simply substitute the calculated value of ΔTf into the equation.