Crystallisation

Q.

Upon heating a solution of salt and water, we get salt as a residue.

1. True

2. False

Q. Explain the process of crystallisation with steps

Q.

The evaporation method is the best method to obtain pure sugar from its solution in water.

1. False

2. True

Q. Why does boiling happens all through the liquid and evaporation only at the surface even though both the processes are quite same? What exactly happens at the molecular level in both the cases?

Q. Copper sulphate can be obtained from its solution by the process of:

1. Filtration
2. Centrifugation
3. Sublimation
4. Crystallisation

Q.

Crystallisation is better than simple evaporation because:

1. solids can decompose

2. the contaminant can still be present

3. may get charred when heated to dryness

4. it occurs spontaneously

Q. What is the important role of a condenser in the distillation of a salt solution?

1. It changes the water vapour into liquid.
2. It changes the water vapour into solid.
3. It cools the water vapour.
4. It increases the temperature of the solution.

Q.

Common salt is purified by ______________( centrifugation/crystallisation) method.

Q.

The pure crystals of copper sulfate are obtained by the process of crystallization.

1. True
2. False

Q.

How will you obtain reasonably pure samples of iron fillings, common salt, and, Sulphur from their mixture?

Q. is the common solvent used in the process of crystallization.

1. Sulphuric acid
2. Water
3. Nitric acid

Q.

Match the statements of Column A with those of Column B.

Column 1	Column 2
Solvent extraction	Difference in densities
Gravity method	Size of the particles of insoluble solid
Sublimation	High density of insoluble solid
Fractional crystallization	Solubility of one component in a solvent
.	Ability of one component to sublime
-	Difference in solubility of the components in the same solvent at a certain temperature range

Q. What is the important role of a condenser in the distillation of a salt solution?

1. It cools the water vapour.
2. It changes the water vapour into liquid.
3. It changes the water vapour into solid.
4. It increases the temperature of the solution.

Q.

What separation techniques will you apply for the separation of the following:

Sodium chloride from its solution in water.

Q. state the differences between evaporation and boiling

Q.

What type of mixture is separated by the technique of crystallisation?

1. Solid-Solid
2. Liquid-Liquid
3. Gas- Liquid
4. Solid-Liquid

Q.

State briefly how would you separate and name the process usedto separate:

1-Sulphur from a mixture of carbon particles and powdered roll sulphur.

2-A precipitate of lead sulphate obtained by adding sulphuric acid to a solution of lead nitrate.

3-Nitrogen from liquid nitrogen.

4-Oxygen from a mixture of oxygen and ammonia.

5-Hydrogen from a mixture of hydrogen and carbon monoxide.

Q. Evaporation is the physical process in which a changes to a below boiling point.

1. solid
2. liquid
3. gas
4. semi-solid

Q.

____________ is a process that separates a pure solid in the form of its crystals from a solution.

1. Filtering

2. Crystallisation

3. Phase change

4. Solidification