Question

Iodine can be separated from sodium chloride by

• A. Sublimation
• B. Distillation.
• C. Evaporation
• D. Chromatography.

Answer 1

The correct option is A

Sublimation

The explanation for correct option:
(A) Sublimation

Principle: This process is used to separate a mixture in which one constituent sublimes.

• Sublimation is the process in which a solid directly changes to a gas without passing through the liquid state.
• A substance is said to be sublime if it passes from the solid state directly into the gaseous state without changing into a liquid.
• Substances such as ammonium chloride, camphor and naphthalene undergo sublimation.
  

The explanation for incorrect options:
(B) Distillation.

• Distillation is the process of separating a liquid from its solution by evaporating it and then condensing its vapor.
• The process is carried out in a specially designed apparatus called the distillation flask.
• A solution is heated in the distillation flask due to which the liquid component gets evaporated, leaving the solid component behind.
• The vapor of the liquid pass through a tube called the condenser.
• The condenser is kept cool so that vapor can cool down.
• Finally, the vapor are collected in a receiving flask. This way, we get pure liquid from its solution.
• The distilled water that is used by doctors, chemists and pharmaceutical industries is obtained by distillation.

(C) Evaporation

• The process by which a liquid is converted into its vapor state is called evaporation.
• The rate of evaporation increases with an increase in temperature.
• Evaporation is used to separate a solid component from a homogeneous mixture of solids and liquids.
• The process of evaporation involves heating the solution until the solvent evaporate and turns into gas leaving behind the solid residue.
• For example, we can separate salt from a mixture of salt and water using evaporation. We heat the solution to a boiling point to obtain salt from salt water.
• As the solution boils, the water escapes as vapor and after some time all the water evaporates leaving a layer of salt at the bottom of the beaker.
  

(D) Chromatography.

• This is one of the latest techniques to separate the components of a mixture, when all the components are very similar in their properties.
• Chromatography is a technique that is used to separate a mixture of chemicals in a liquid or gaseous form based on the differences in adsorbency (the quality of being able to adsorb something easily).
• The technique of chromatography is based on the principle of selective adsorption (surface adsorption) of different components on the surface of a suitable adsorbent.
• Chromatography consists of a mobile phase and a stationary phase.
• Mobile phase is a fluid or a solvent which carries the components of the mixture to be separated through the fixed column.
• Stationary phase is the column that stays fixed and the solvent moves through it.
• For example, in paper chromatography, the paper is the stationary phase and the solvent might be water or any other solvent that helps to separate the constituents of the mixture.
  

Hence option A is correct.