Question

You are performing a simple distillation of roughly 50:50 liquid solution containing two components, hexane and nonane You place 15 ml of the mixture in a round bottom flask, and then collect the distillate sequentially as four three ml samples labeled S1, S2, S3, and S4. Pure hexane has a refractive index of 1.375 and pure nonane has a refractive index of 1.407. You measure a refractive index of 1.3964 for one of the four samples. Assuming the refractive index varies linearly with mole fraction, estimate the mole fraction of hexane in this sample.
a) .67

b).33

Answer 1

a) 0.67 because it is mentioned that R.I. varies linearly with mole fraction. Hence pure hexane which has R.I. of 1.375 and that of 1.3964 for one of the 4 samples implies that mole fraction of hexane in the sample is 0.67.