(a) Calculate the molar mass of the unknown compound. The freezing point of benzene is 5.48°C, and the Kf of benzene is 5.12 °C/Molal. Show your work
There isn't enough information.
2. When 0.354 g of an unknown nonelectrolyte compound was dissolved in 12.5 g of benzene a solution was formed that froze at 4.46°C.
(a) Calculate the molar mass of the unknown compound. The freezing point of benzene is 5.48°C, and the Kf of benzene is 5.12 °C/Molal. Show your work
I worked this for you an hour or so ago. Look at your original post.
To calculate the molar mass of the unknown compound, we need to use the freezing point depression equation. The equation is as follows:
ΔT = Kf * m * i
Where:
ΔT = difference in freezing point (in °C)
Kf = freezing point depression constant (in °C/m)
m = molality of the solution (in mol/kg)
i = van't Hoff factor (a factor that represents the number of particles into which a compound dissociates)
In this case, benzene is the solvent, and the freezing point depression constant (Kf) for benzene is given as 5.12 °C/Molal.
We are given that the freezing point depression (ΔT) is 5.48°C. To calculate the molality (m), we rearrange the equation as follows:
m = ΔT / (Kf * i)
Since we don't know the van't Hoff factor (i) for the unknown compound, we assume it to be 1 unless otherwise specified. Substituting the values into the equation:
m = 5.48°C / (5.12 °C/Molal * 1 Molal)
Simplifying the units:
m = 5.48 / 5.12 Molal
m ≈ 1.07 Molal
Now, we can calculate the molar mass of the unknown compound using the equation:
molar mass = (ΔT / Kf) / m
Substituting the values:
molar mass = (5.48 °C / 5.12 °C/Molal) / 1.07 Molal
molar mass ≈ 1.06
Therefore, the molar mass of the unknown compound is approximately 1.06 g/mol.