A solution contains 20g of C^6H^12O^6 in 250g of water. What is the freezing-point depression of the solvent? What is the Freezing point of the solvent?
moles = grams/molar mass.
Calculate moles.
m = moles/kg solvent.
Calculate m
delta T = Kf*m
Calculate delta T.
The freezing point of the solvent, normally, is 0o C.
The freezing poing depression constant for the solvent, H2O, is 1.86 o/m. You may have rewritten the problem, but, as stated, it does not ask for the freezing point of the solution. The first three steps, however, will calculate that. The other two numbers, the normal freezing point and the freezing point depression constant can be looked up in tables.
To determine the freezing-point depression of the solvent, we need to use the equation:
ΔT = Kf * m
where:
ΔT = freezing-point depression
Kf = cryoscopic constant of the solvent
m = molality of the solute
To find the molality of the solute (C6H12O6), we can use the formula:
m = (moles of solute) / (mass of solvent in kg)
First, let's calculate the moles of solute (C6H12O6):
moles of solute = mass of solute / molar mass of solute
The molar mass of C6H12O6 can be calculated as follows:
(6 * atomic weight of carbon) + (12 * atomic weight of hydrogen) + (6 * atomic weight of oxygen)
Now, let's calculate the mass of solute:
mass of C6H12O6 = 20g
Next, we need to calculate the mass of solvent in kg:
mass of water = 250g = 0.25kg
Using the calculated values, we can find the moles of solute and the molality of the solute. Then we can use the cryoscopic constant of water (Kf = 1.86 °C/m) to find the freezing-point depression (ΔT).
To find the freezing point of the solvent, we can use another equation:
ΔT = Kf * i * m
where:
i = van 't Hoff factor
For most non-electrolyte solutes dissolved in water, the van 't Hoff factor (i) is considered 1. Therefore, we can calculate the freezing-point depression (ΔT) and then subtract it from the normal freezing point of water (0°C) to obtain the freezing point of the solvent.
Let's now calculate the freezing-point depression and the freezing point of the solvent.