Answer:- molar mass of menthol is 156.06 g/mol.
Solution:- delta Tf = i x m x kf
where, delta Tf is depression in freezing point.
i is Van't hoff factor, m is molality and kf is the molal freezing point constant.
menthol is covalent molecule and so the value of i for this is 1 as it does not give ions.
delta Tf = 5.49 degree C
kf for cyclohexane is 20.8 degree C/m
Let's plug in the values in the formula..
5.49 = 1 x m x 20.8
m = 5.49/20.8
m = 0.264
molality = moles of solute/kg of solvent
There are 25.0 g that is 0.025 kg of solvent.
So, 0.264 = moles of solute/0.025
moles of solute = 0.264(0.025) = 0.0066
moles = mass/molar mass
So, molar mass = mass/moles
molar mass = 1.03 g/0.0066 mol
molar mass = 156.06 g/mol