Free Sublimation and Distillation MCQs with Answers

1. The separation of components of liquid on the basis of their boiling points is called as?

• A. Destructive distillation
• B. Fractional distillation
• C. Vacuum distillation
• D. Partial distillation

Explanation: Destructive distillation is a process that involves heating organic material in the absence of air or oxygen to break it down into simpler chemical compounds. Fractional distillation is a process used to separate a mixture of two or more liquids with different boiling points. This process relies on the fact that each liquid in the mixture has its own unique boiling point. Vacuum distillation is a type of distillation used to separate materials with high boiling points or those that are sensitive to heat. In vacuum distillation, the pressure inside the distillation apparatus is lowered, which reduces the boiling point of the material being distilled. There is no such term as partial distillation.

2. What are the products of destructive distillation of coal?

• A. Coal tar
• B. Coke
• C. Coal gas
• D. All of above

Explanation: Destructive distillation is a chemical process in which decomposition is achieved by heating to a high temperature; the term generally applies to the processing of organic material in the absence of air or in the presence of limited amounts of oxygen. The process breaks up large molecules. 'Coke, coal gas, gaseous carbon, coal tar, ammonia liquor ,and coal oil' are examples of commercial products historically produced by the destructive distillation of coal.

3. Rectified spirit is converted into the absolute alcohol by _.

• A. Crystallization
• B. Distillation
• C. Re-distillation
• D. Fractional distillation

Explanation: c) Re-distillation: Re-distillation is essentially the same as distillation. It is the process of distilling a liquid multiple times to achieve higher purity. In the case of converting rectified spirit into absolute alcohol, the process would involve re-distillation.

4. In a vacuum distillation the boiling point of glycerin is reduced to _?

• A. 290°C
• B. 110°C
• C. 156°C
• D. 210°C

Explanation: Correct option is D. Under vacuum, the boiling temperature of glycerin decreases to 210°C at 50 torr. It is distilled at this temperature without decomposition for purification. Vacuum distillation is the distillation carried on under reduced pressure so that the liquid being distilled boils at a lower temperature than under atmospheric pressure and consequently with less chance of decomposition compared to molecular distillation.

5. The acid which can be purified by the sublimation is:

• A. Acetic Acid
• B. Oxalic Acid
• C. Benzoic Acid
• D. Citric Acid

Explanation: Explanation:Benzoic acid has a high melting point (122°C) and a low vapor pressure, which allows it to sublime at room temperature and atmospheric pressure. Hence, the acid which can be purified by the sublimation is benzoic acid.Acetic acid has a low boiling point (118.1°C) and cannot be purified by sublimation. Oxalic acid has a decomposition temperature lower than its melting point, so it cannot be purified by sublimation. Citric acid has a decomposition temperature lower than its melting point, so it cannot be purified by sublimation.

6. Sublimation is used to purify:

• A. Ammonium sulphate
• B. Sodium chloride
• C. Benzoic acid
• D. Lead carbonate

Explanation: A is incorrect as ammonium sulphate is purified through centrifuging.B is incorrect as sodium chloride is purified by crystallization.C is correct as benzoic acid is purified through sublimation.D is incorrect as lead carbonate is purified through sulfation, desulfurization leaching, distillation and carbonization.

7. For the separation of gases from a mixture we use:

• A. Simple diffusion
• B. Fractional distillation
• C. Chromatography
• D. Graham's law of diffusion

Explanation: Fractional distillation is the special technique which is used for separation of mixture of two gases

8. Which one of the following is used as a drying agent?

• A. NaHCO3
• B. CaCO3.H2O
• C. CaCl2 anhydrous
• D. Na2SO4.H2O

Explanation: CaCl2 (anhydrous calcium chloride): Calcium chloride is a widely used drying agent due to its strong hygroscopic properties. It effectively absorbs moisture from the air, making it useful for drying applications in laboratories, industries, and even for de-icing roads.