I need to calculate the molecular mass of ehtylene glycol based on the freezing point depression.

The teacher said that for glycol i=1 and to use the equation
m=delta T / Kf X i

Kf = -1.86C/m

so I did -2.5C / -1.86 X 1 = 1.344

I know that 1.344 can't be the weight for glycol but im not sure what to do now? Should i multiply by 1000?

1.344 is the molality.

Then molality = mols/kg solvent
Plug in kg solvent and m and solve for moles
Then mols = g/molar mass.
Rearrange to molar mass = g/mols. You know how much (grams) you used and you know mols, solve for molar mass.

the only info that I have is the mass of solute(g) and mass of solvent(kg) for glycol so im confused on what to use for mols?

Disregard question I understand now. I have to solve for mols.

so for molality I got 1.344 then I did

1.344 = mols/0.10kg = 0.1344 Im not sure if I did this step right

Then I did mm= g/mol
6.200 was the mass of the solute so
mm=6.200 / 0.1344 = 46.13.

I guess I made a mistake somewhere in my calculations because I thought that the mm of eythlene was around 62.

To calculate the molecular mass of ethylene glycol based on the freezing point depression, you need to follow a few steps. Let's go through them together:

Step 1: Calculate the molality (m) of the ethylene glycol solution.
You have correctly identified that Kf (the freezing point depression constant) for ethylene glycol is -1.86°C/m. Given the change in freezing point (delta T) as -2.5°C, you can plug these values into the equation:

m = delta T / Kf
m = -2.5°C / -1.86°C/m
m ≈ 1.34 m

So, the molality of the solution is approximately 1.34 m.

Step 2: Determine the number of particles (i) ethylene glycol dissociates into.
According to your teacher, for glycol (ethylene glycol), i = 1. This means that ethylene glycol does not dissociate into multiple particles in solution, and each molecule of ethylene glycol contributes as a single particle.

Step 3: Calculate the molecular mass (m) of ethylene glycol.
Now, you can rearrange the original equation m = delta T / Kf X i to solve for m (molecular mass). We can write it as:

m = delta T / (Kf X i)
m = -2.5°C / (-1.86°C/m X 1)
m ≈ 1.34 m

The value you obtained, 1.344, is the molality, not the molecular mass. So, it seems there might be some confusion here.

To find the molecular mass of ethylene glycol, you need additional information such as the mass of the solvent used or the mass percentage of ethylene glycol in the solution. Without this information, it is not possible to directly calculate the molecular mass of ethylene glycol from the freezing point depression alone.

Multiplying the value by 1000 won't give you the molecular mass; it will only convert the units from mol/kg to mol/g if that's what you're aiming for.

If you have additional information or clarifications about the problem, please share them, and I'll be happy to assist you further!