If 1373 g of a substance is dissolved in 2315 g of cyclohexane solvent, the boiling point of the solution is 87.69 oC. Calculate the apparent molar mass (g/mol) of substance.

Answered below.

To calculate the apparent molar mass of the substance, we need to use the formula for boiling point elevation:

ΔTb = Kbm

Where:
- ΔTb is the boiling point elevation
- Kb is the molal boiling point elevation constant
- m is the molality of the solute

First, let's calculate the molality (m) of the solute in the solution.

Molality (m) is defined as the amount of moles of solute per kilogram of solvent. In this case, we have 1373 g of the substance dissolved in 2315 g of cyclohexane solvent.

First, we need to convert the given masses into moles using the molar mass of each component.

Let's assume the molar mass of the substance is M (g/mol).
The number of moles of the substance (n) is given by:

n = mass / molar mass
n = 1373 g / M g/mol

Similarly, the number of moles of cyclohexane solvent is given by:

n(solvent) = mass / molar mass
n(solvent) = 2315 g / 84.16 g/mol (molar mass of cyclohexane)

The molality (m) is defined as the moles of solute divided by the mass of the solvent in kg:

m = n / mass(solvent)
m = n / (mass(solvent) / 1000) (from g to kg)

Now we can substitute the values into the boiling point elevation formula:

87.69 oC = Kb * m

We need to look up the molal boiling point elevation constant (Kb) for cyclohexane, which is typically given as 2.76 oC/m.

Let's solve for m:

m = 87.69 oC / (2.76 oC/m)
m = 31.75 m

Finally, let's solve for the molar mass (M) of the substance:

31.75 m = n / (mass(solvent) / 1000)
31.75 m * (mass(solvent) / 1000) = n
31.75 * (2315 g / 84.16 g/mol) = n
874.97 = n

Therefore, the apparent molar mass of the substance is approximately 874.97 g/mol.