Question

2. Aliquid mixture contains two substances whose boiling points are only 10°C apart. Which method of distillation should be utilized to obtain a clean separation of the two substances. Explain. 3. Which of the following pairs of liquids could be separated by simple distillation? Why? a. Ethyl acetate (b.p. 77°C) & Phenol (b.p. 181.7°C) b. Cyclohexane (b.p. 80.7°C) & Toluene (b.p. 111C) C. Hexane (b.p. 69.10C) & Ethylbenzene (b.p. 136°C) 4. What effect would (a) an increase or (b) a decrease in the pressure have on the boiling point of a liquid? 5. When isolation of a product from a reaction mixture is carried out, a solvent is generally used to extract the product before purification. What boiling point characteristic must this solvent have in order to facilitate its easy separation from the product you want to isolate?

Answer 1

2. Here the boiling point difference is 10^o C so we will use Fractional Distillation. In fractional distillation the distillation column has multiple plates inside it and we heat from bottom and the substance which is less volatile get collected from lower plates and which is more volatile & lower boiling point get collected from upper plates.

3. For simple distillation the difference in boiling point of substances should be atleast 35 - 40 ^oC so the correct option will be (A) and (C) because here difference in boiling point is more tgan 40 degree C.

4. The boiling point of a substance is the temprature when its vapour pressure become equal to the external pressure and vapour pressure iis directly proportional to temprature or boiling temeprature so on increasing the pressure boiling point increases and on decreasing the temprature the boiling point decreases.