A mixture of methanol (Mw = 32.04 g/mol) and ethanol (Mw = 46.07 g/mol) has an average molecular weight of 43.01 g/mol. What is the mol fraction of methanol in this mixture?

The mole fraction of methanol in this mixture is 0.745

Explanation:

Molecular weight of methanol in the mixture = 32.04g/mol

Molecular weight of ethanol in the mixture = 46.07g/mol

Average molecular weight of mixture = 43.01g/mol

Mole fraction of methanol = molecular weight of methanol : average molecular weight of mixture = 32.04g/mol : 43.01g/mol = 0.745

The mol fraction of methanol is 0.2181

Explanation:

Step 1: Data given

Molar mass of methanol = 32.04 g/mol

Molar mass of ethanol = 46.07 g/mol

Average molecular weight = 43.01 g/mol

Step 2: Calculate the mol fraction of methanol

Mol fraction = number of moles / total number of moles

We know that mol fraction of methanol + mol fraction of ethanol = 1

Mol fraction methanol = 1 - mol fraction of ethanol

X = 1-Y

Let's consider methanol = X and ethanol = Y

32.04*X + 46.07*Y = 43.01

32.04 * (1-Y) + 46.07Y = 43.01

32.04 - 32.04Y + 46.07Y = 43.01

14.03 Y = 10.97

Y = 0.7819

The mol fraction of ethanol is 0.7819

The mol fraction of methanol is 1 - 0.7819 = 0.2181