A solution was made by dissolving 62.07 grams of a compound in 500g of water. The compound was not ionic. The freezing point of the solution was measured and found to be -1.86 degrees celsius. Using the Kf value in your textbook, the molar mass of this conpound can be calculated to be?
I am not sure what Kf value they are referring to for me to find. Would I use the freezing point equation for this?
Yes, delta T = Kf*m
Solve for m
Then m = mols/kg solvent
You know m and kg solvent, solve for mol.
Then mol = grams/molar mass
You know mol and grams, solve for molar mass.
so delta T would be 1.86 but Im not sure what Kf would be?
Kf = Kf = Kf. What have you been using for Kf for water? Isn't that 1.86. I know what's confusing you. delta T = 1.86 and Kf is 1.86. Just plug it into the equations and the math will work out.
To calculate the molar mass of the compound, you need to use the freezing point depression equation and the value of the cryoscopic constant (Kf) specific to the solvent being used. In this case, the solvent is water.
The freezing point depression equation is given by:
∆Tf = Kf * m * i
Where:
- ∆Tf is the change in freezing point (in this case, -1.86 degrees Celsius)
- Kf is the cryoscopic constant for water (which you need to find in your textbook)
- m is the molality of the solution, calculated as moles of solute (compound) per kilogram of solvent (water)
- i is the van't Hoff factor, which represents the number of particles produced when the compound dissolves (for a non-ionic compound, i = 1)
To find the molar mass, we need to rearrange the equation:
Molar mass (g/mol) = (Kf * m * i) / ∆Tf
In this case, we are given the mass of the compound (62.07 grams) and the mass of the solvent (500 grams). To find the molality, we need to convert the mass of the compound to moles, then divide by the mass of the solvent in kilograms.
Steps to find the molar mass:
1. Convert the mass of the compound to moles:
Moles of compound = mass of the compound / molar mass of the compound
2. Calculate the molality (m):
moles of compound = m * kg of solvent
So, m = moles of compound / kg of solvent
3. Find the cryoscopic constant (Kf) for water in your textbook.
4. Substitute the values into the equation:
Molar mass (g/mol) = (Kf * m * i) / ∆Tf
By following these steps, you can determine the molar mass of the compound.