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 1.3948 for one of the four samples. Assuming the refractive index varies linearly with mole fraction, estimate the mole fraction of hexane in this sample.

Question

Grady Sherman

Chemistry

15 October, 00:48

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 1.3948 for one of the four samples. Assuming the refractive index varies linearly with mole fraction, estimate the mole fraction of hexane in this sample.

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General · Answer 1

0.38

Explanation:

As you go from 0 % hexane (χ = 0) to 100 % hexane (χ = 1), the refractive index decreases from 1.407 to 1.375, a decrease of 0.032.

From 1.407 to 1.3948, the decrease is 0.0122.

That is 0.0122/0.032 = 0.38 of the distance from χ = 0 to χ = 1.

The mole fraction of hexane is 0.38.

The diagram below is a plot of refractive index vs. the mole fraction of hexane. It shows that the refractive index drops to 1.3948 when χ = 0.38.