Question

How can we recover pure sugar from sugar solutions?

• A. by distillation
• B. by filtration
• C. by crystallization
• D. by evaporation to dryness

Answer 1

The correct option is C

by crystallization

Explanation of correct option:

(c) Crystallisation:

1. It can be defined as the process through which the atoms/molecules of a substance arrange themselves in a well-defined three-dimensional lattice and consequently, minimize the overall energy of the system.
2. Crystallization is a technique used for the purification of substances.
3. Crystallization is a process that separates a pure solid in the form of its crystals from a solution.
4. Pure sugar from sugar solution can be obtained by crystallization.

Explanation of incorrect options:

(a) Distillation:

1. Distillation is defined as the selective boiling and subsequent condensation of a component in a liquid mixture.
2. The technique used to separate the mixture of miscible mixtures of liquids having a boiling point difference of more than $25°\mathrm{C}$.
3. In this process, the liquid is heated to its boiling point so that it is converted into vapors. On cooling the vapors, the pure liquid is obtained and collected separately.
4. The whole component having a low boiling point is collected in the receiver and the other component having a high boiling point remains in the flask.
5. Example - a mixture of acetone (boiling point $56°\mathrm{C}$) and water (boiling point $100°\mathrm{C}$), purification of alcohol, and crude oil refining.

(b) Filtration:

1. It is defined as the process of separating suspended solid matter from a liquid by causing the latter to pass through the pores of a membrane, called a filter.
2. It is used to separate insoluble solids in a liquid.
3. For example, it is used to separate sand from the mixture of sand and water.
4. Filtration can't be used as sugar is completely dissolved in water so it passes through the filter paper completely.

(d) Evaporation:

1. It is the process of separating any substance from its solution by removing water.
2. For example, it is used to separate soluble components like common salt from the salt solution.
3. But in this case, evaporation will decompose the sugar on heating.

Hence, option (c) is the correct option.