Determine the molar mass of a compound and its molecular formula if a solution of 1.00 g of the unknown is dissolved in 50 grams of cyclohexane. Cyclohexane freezes at 6.02 oC. The normal freezing point of cyclohexane is 6.50 oC and its kf value is 20.2 oC/m. The percent composition of the unknown is 85.71% C and 14.29% H

delta T = Kf*m

Substitute and solve for m = molality.

m = mols/kg solvent
You know m and kg solvent, solve for mols.

mols = g/molar mass.
You know mols and g, solve for molar mass. I obtained in the neighborhood of 842 as the approximate molar mass.

For the compound with 85.71%C and 14.29%H, convert to mols.
85.71/12 = about 7.14 mols C
14.29g/1 = 14.29 mols H which is a ratio of CH2. That's the empirical formula with an empirical mass of 14
842/14 = about 60.2 which rounds to 60 so the molecular formula is (CH2)60 or C60H120 with a more accurate molar mass of (60*12 + 120*1) = ?

To determine the molar mass of the compound and its molecular formula, we need to collect some information and perform calculations step by step. Here's how you can approach the problem:

Step 1: Calculate the freezing point depression (∆Tf):
∆Tf = Tf(normal) - Tf(solution)
= 6.50 oC - 6.02 oC
= 0.48 oC

Step 2: Calculate the molality (m) of the solution:
m = moles of solute / mass of solvent (in kg)

First, let's calculate the mass of cyclohexane in the solution:
mass of cyclohexane = 50 g

Next, calculate the moles of cyclohexane (the solvent):
moles of cyclohexane = mass of cyclohexane / molar mass of cyclohexane

The molar mass of cyclohexane (C6H12) can be calculated as follows:
molar mass of C = atomic mass of carbon
molar mass of H = atomic mass of hydrogen

molar mass of C = 12.01 g/mol
molar mass of H = 1.008 g/mol

molar mass of cyclohexane = (6 * molar mass of C) + (12 * molar mass of H)
= (6 * 12.01 g/mol) + (12 * 1.008 g/mol)

Now, divide the mass of cyclohexane by its molar mass to obtain the moles of cyclohexane.

Step 3: Calculate the moles of solute (unknown compound):
moles of solute = (moles of cyclohexane) * (moles of solute / moles of cyclohexane)

To determine the moles of solute, we need to first determine the moles of carbon (C) and hydrogen (H) in the compound, based on the given percent composition.

Percent composition can be converted into grams:
mass of carbon (in g) = (85.71% / 100%) * 1.00 g
mass of hydrogen (in g) = (14.29% / 100%) * 1.00 g

Now, convert the mass of carbon and hydrogen into moles:
moles of carbon = mass of carbon / molar mass of carbon
moles of hydrogen = mass of hydrogen / molar mass of hydrogen

Step 4: Determine the empirical formula of the compound:
Divide the moles of each element in the compound by the smallest number of moles obtained. Then, round the ratios to the nearest whole number.

Step 5: Calculate the molecular formula:
The molecular formula can be determined by multiplying the empirical formula by a whole number (n). To find this value, we need additional information like the molar mass of the compound.

By following these steps, you can determine both the molar mass and molecular formula of the compound.