Vitamin K is involved in normal blood clotting. When 1.05 g of vitamin K is dissolved in 25.0 g of camphor, the freezing point of the solution is lowered by 3.53 °C. The freezing point and Kf constant for camphor can be found here. Calculate the molar mass of vitamin K.
I honestly have no idea what it is that I'm doing wrong. I think my initial equation of DTf = Kf * m might be wrong, therefore throwing off the rest of the problem. Please help.
To solve this problem, you need to use the freezing point depression equation and apply it to the given information.
The freezing point depression equation is: ΔTf = Kf * m * i
Where:
- ΔTf is the freezing point depression (change in freezing point) of the solvent (camphor) when a solute (vitamin K) is added.
- Kf is the cryoscopic constant, which is specific to the solvent.
- m is the molality of the solution, defined as the moles of solute divided by the mass of the solvent (in kg).
- i is the van't Hoff factor, which represents the number of particles that the solute dissociates into in the solvent. For non-ionic solutes like vitamin K, i is equal to 1.
Given information:
- Mass of vitamin K: 1.05 g
- Mass of camphor: 25.0 g
- Freezing point depression (ΔTf) of camphor solution: -3.53 °C
First, you need to convert the masses of vitamin K and camphor to moles:
- Mass of vitamin K: 1.05 g
- To convert to moles, divide by the molar mass of vitamin K.
- To find the molar mass of vitamin K, you need to use the given freezing point and Kf constant for camphor.
Now, let's calculate the molality (m) of the solution:
- Molality (m) is defined as moles of solute per mass of solvent (in kg).
- The mass of the solvent is given as 25.0 g, so you need to convert it to kg by dividing by 1000.
- Moles of solute (vitamin K) can be calculated by dividing the mass of vitamin K by its molar mass (which we will find).
Next, you can use the freezing point depression equation to calculate the molar mass of vitamin K.
Here is the step-by-step breakdown of the calculations:
1. Convert the mass of camphor to moles:
- Mass of camphor = 25.0 g
- Molar mass of camphor (Kf constant) can be found using the given freezing point depression and Kf constant for camphor.
2. Calculate the molality (m) of the solution:
- Molality (m) = moles of solute / mass of solvent (in kg)
3. Calculate the moles of solute (vitamin K):
- Moles of solute = mass of vitamin K / molar mass of vitamin K
4. Use the freezing point depression equation to find the molar mass of vitamin K:
- ΔTf = Kf * m * i
- Rearrange the equation to solve for the molar mass of vitamin K.
By following these steps, you should be able to calculate the molar mass of vitamin K.
formula is correct, the issue is molality.
1.05/molmassK*.025
so,
molmassK=1.05Kf/(.025*3.53)