Vitamin K is involved in normal blood clotting. When 1.56 g of vitamin K is dissolved in 25.0 g of camphor, the freezing point of the solution is lowered by 5.23 °C. . Calculate the molar mass of vitamin K.
delta T = Kf*m
Substitute and solve for m = molality.
m = mols solute/kg solvent
Substitute and solve for mols solute
mols = grams/molar mass. You have grams and mols, solve for molar mass.
When i did the problem i got 0.76 but i think its wrong?
To calculate the molar mass of vitamin K, we can use the freezing point depression equation:
ΔT = K_f * m * i
Where:
ΔT = change in freezing point (in degrees Celsius)
K_f = freezing point depression constant for the solvent
m = molality of the solute (moles of solute per kilogram of solvent)
i = van't Hoff factor (the number of ions or particles the solute dissociates into)
First, we need to calculate the molality (m) of the solute. To do this, we need to find the number of moles of vitamin K and the mass of the camphor.
1.56 g of vitamin K is dissolved in 25.0 g of camphor. Since we are given the mass of the solvent (camphor), we can calculate the mass of the solute (vitamin K) by subtracting the mass of the camphor from the total mass of the solution:
Mass of vitamin K = Total mass of solution - Mass of camphor
= 1.56 g - 25.0 g
= -23.44 g
Note: The negative sign indicates that the mass of vitamin K is subtracted from the mass of camphor.
Now, we need to convert the mass of vitamin K into moles using its molar mass (M). The molar mass can be calculated using the equation:
Molar mass (g/mol) = Mass (g) / Moles (mol)
To find the moles of vitamin K, rearrange the equation:
Moles (mol) = Mass (g) / Molar mass (g/mol)
Next, we can calculate the molality (m) using the equation:
Molality (m) = Moles of solute (mol) / Mass of solvent (kg)
Since we have the mass of camphor in grams, we need to convert it to kilograms:
Mass of camphor (kg) = Mass of camphor (g) / 1000
Now, we can substitute the values into the freezing point depression equation:
ΔT = K_f * m * i
Given that the freezing point depression constant for camphor is K_f = 40.0 °C/m, and the change in freezing point (ΔT) is 5.23 °C, we can solve for the molality (m).
Finally, once we have the molality (m), we can use it to calculate the moles of vitamin K and then find its molar mass using the equation:
Molar mass (g/mol) = Mass (g) / Moles (mol)
By following these steps, we can determine the molar mass of vitamin K.