Separation Techniques

Mixture of sand and water can be separated by the methods of sedimentation and decantation.

This option is correct because all of the above methods can be used for preparation of colloidal crystals.

Centrifugation is the process for separating the fine suspended particles of substances in a liquid by rotating the liquid in a closed container. Washing machine works on the principle of centrifugation.

In this process, pure sample of soluble solid is obtained from its solution by reducing the temperature. In this process liquid solution of a solid is heated and then filtered. Through this, unwanted impurities are removed and then, after cooling  the filtrate in a ice bath, crystals of pure solid are fomed. This process is based on three levels-heating, filtering and cooling, so all are impurities are removed and we get ultra pure substance.

Electrolysis is the process of separating the components of a homogeneous mixture using electricity.

Yes, it is done by fractional distillation which is based on the boiling point.

In municiple water works first loading, sedimentation, decantation and then filtration is done.

Cream is separated from milk by centrifugation because on rotating the milk, cream comes up.

Because sulphur is insoluble in water so it is separated through filtration.

Statement (1) is correct. Froth flotation is one of the processes used to recycled paper. In the paper industry this step is called deinking or just flotation. The target is to release and remove the hydrophobic contaminants from the recycled paper. The contaminants are mostly printing ink and stickies. Statement (2) is correct. Distillation is the process of heating a liquid to its boiling point, capturing and cooling. Extraction of petroleum, diesel, naphthalene and bitumen is the example of fractional distillation.

Both Claude process and Linde process can be used for the liquefaction of air. 

In chemistry, fractional crystallisation is the method of refining substances based on differences in solubility. If a mixture of two or more substances in solution is allowed to crystallise, e.g. by allowing the temperature of the solution to decrease, the precipitate will contain more of the least soluble substance.

Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. Sublimation is an endothermic phase transition that occurs at temperatures and pressures below the triple point of a substance in its phase diagram.

Crystallisation is the process in which crystals of a pure substance are obtained by cooling its hot saturated solution. This technique is used for purification of inorganic/organic solids. This is based upon the principle that when a crystal is formed, it tends to exclude the impurities which remain in the solution. Centrifugation is the process of separating the suspended particles from a liquid mixture by rotating the mixture at high speed. This technique is based on the fact that denser particles are forced to the bottom and lighter particles stay at the top when spun rapidly. Sublimation is the process of separating a sublimable volatile component (i.e. substance which changes directly from solid to gas, without going through the intervening liquid state, on heating and vice-versa on cooling) from non–sublimable impurities whereas evaporation is the technique used to separate non–volatile components (solutes) dissolved in volatile solvents, i.e. in this technique, an impure solid is obtained from its solution. 

(1) Separation of cream from milk - Centrifugation (2) Separation of oil from water - Separating funnel (3) Separation of pigment from natural colours - Chromatography (4) Separation of components of air - Fractional distillation