Question

There is a mixture of three solid compounds A,B and C. Out of these compounds A and C are soluble in water and compound C is sublimable also. In what sequence the following techniques can be used for their respective separation?
I. Filtration
II. Sublimation
III. Crystallization from water extract
IV. Dissolution in water
Which of the following options is corrcet?
A. (II),(I),(IV),(III)
B. (IV),(I),(II),(III)
C. (I),(II),(III),(IV)
D. (II),(IV),(I),(III)

Answer 1

There are multiple ways of separating the given mixture of solids. We need to make sure that we choose a series of methods which could reduce the amount of effort and energy in doing the same work.

Complete Step by step answer: Firstly we will define each of the given process
(I) Filtration: It is the process of separation of suspended solid particles from a liquid by causing the latter to pass through the pores of some substance, called a filter. The liquid which has passed through the filter is called the filtrate.
(II) Sublimation: It is a type of phase transition, or a change in a state of matter, just like melting, freezing, and evaporation. Through sublimation, a substance changes from a solid to a gas without ever passing through a liquid phase. This method can be used to separate sublimable substances from non-sublimable substances.
(III) Crystallization from water extract: This technique involves the separation of solid from its solution based on the principle that the solid(solute) is soluble in hot solvent but insoluble when the solute becomes cold.
(IV) Dissolution in water: This is a basic principle of dissolving the given solid mixture in water. Different solutes have different solubilities in water which can be used as the principle to separate a mixture in its constituents.

Now in this case it is best to first separate C from the mixture as it is sublimable. So we apply (II)Sublimation to the mixture. The remaining mixture consists of A and B. Now the mixture undergoes (IV)Dissolution in water as B is insoluble in water and can be separated by further (I)Filtration. The remaining solid A is present along with water and can be extracted using (III)Crystallization from water extract.

Hence the correct option is D.

Note: Water is used as the solvent as it is cheap and easily available. Changing the order may also get us the desired separated solids but it cannot be used as this is the most efficient series of methods and requires least effort.