Question

2. Why don’t we expect our distillations to result in 100% hexane purity?

3. What peaks would you expect to observe in the IR spectrum of hexane? Of toluene?

4. Liquid A has a refractive index of 1.415 and liquid B has a refractive index of 1.524. A solution

is prepared by mixing liquid A with liquid B. If the refractive index of the resulting solution is

1.457, does the solution have more of liquid A or more of liquid B? What is the % Liquid A in

the mixture?

Answer 1

2. Because on having a mixture of hexane (b.p= 69^oC) and toluene (b.p= 110^oC)the resulting mixture will have a boiling point between both the liquids. When the resulting mixture is heated and boils, it is not only hexane which goes in the vapour phase but some toluene also adds up in the vapour phase. As a result we do not get 100% pure hexane.

3. In IR spectrum there will be presence of aromatic band (vibration bands for C=C stretching at 1615, 1509,1465 cm^-1) for toluene which will be absent in case of hexane.