Question

Caryophyllene, a nonelectrolyte, is one of the compounds responsible for the flavor of cloves. A 207 mg sample of caryophyllene was dissolved in 1.00g of chloroform (Kb = 3.63 °C/m), increasing the boiling point of chloroform by 3.68°C. What is the molar mass of caryophyllene?

A. 156 g/mol
B. 164 g/mol
C. 204 g/mol
D. 193 g/mol
E. 219 g/mol

Answer 1

C. 204 g/mol. Using the boiling point elevation formula and the given Kb for chloroform, the molality is calculated and thereafter the moles of caryophyllene.

Step-by-step explanation:

To find the molar mass of caryophyllene, we need to utilize the boiling point elevation (ΔTb) equation: ΔTb = iKb*m, where i is the van't Hoff factor (which equals 1 for a nonelectrolyte, as is the case here), Kb is the ebullioscopic constant, and m is the molality of the solution.

First, calculate the molality (m) using the boiling point elevation and the given Kb: m = ΔTb / Kb = 3.68°C / 3.63°C/m = 1.014 m. Next, calculate the moles of caryophyllene: Molality (m) = moles of solute / kg of solvent, 1.014 m = moles of caryophyllene / 0.001 kg, moles of caryophyllene = 1.014 * 0.001 = 0.001014 mol.

Finally, find the molar mass by dividing the mass of caryophyllene by the moles: Molar mass = mass / moles = 0.207g / 0.001014 mol = 204 g/mol.Dividing the mass by the moles gives the molar mass of caryophyllene as 204 g/mol, corresponding to option C.

Therefore, the molar mass of caryophyllene is 204 g/mol, which corresponds to option C.