Question

Given the separation techniques that you have encountered thus far (solvent extraction and distillation), choose the best method to separate each of the following pairs of compounds. Explain your choice.

1. Naphthalene (insoluble in water, solid at room temperature, mp 80 °C, bp 218 °C) and hexanoic acid (liquid at room temperature, mp -3 °C, bp 205 °C).

2. Acetone (liquid at room temperature, bp 56 °C) and toluene (liquid at room temperature, bp 110.6 °C).

3. Cyclohexane (liquid at room temperature, bp 80.7 °C) and pentane (CH3CH2CH2CH2CH3, liquid at room temperature, bp 36 °C).

Answer 1

1) Hexanoic acid is soluble in water, Because it is having the acid functional group it can form the H-bonds with the water.

The Napthalene is insoluble in water by extration with the organic solvents it comes in to the organic layer and Hexanoic acid goes in to the water layer.

2) Acetone and Toluene both are liquids but the Boiling point range is different. These can be separated by Distilation or Fractional distilation.

3) Cyclohexane and Pentane Boiling points also different (the difference is more). These also can be separated by Distillation.