Tag: chemistry

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Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

The process of crystallization begins by:

  1. cooling in ice

  2. evaporation by heating

  3. passing to porous material

  4. none of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Crystallisation is a separation technique that is used to separate. a solid that has dissolved in a liquid and made a solution. The solution is warmed in an open container, allowing the solvent to evaporate, leaving a saturated solution. A solution that has as much solid dissolved in it.

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

After purification by crystallization, copper sulphate crystals can be obtained by :

  1. filtration

  2. passing through funnel

  3. evaporation to dryness

  4. all of above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Impure copper sulphate is dissolved in water and heated till saturation. It is then cooled and crystals of pure copper sulphate are formed. These crystals are then separated by filtration and then dried.

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

Why is crystallization better than evaporation to dryness?

  1. Solids get charred in evaporation

  2. Solids get decomposed in evaporation

  3. Impurities do not get removed in evaporation

  4. All of above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Purification by crystallization is a better technique as compared to evaporation by dryness. Some solids like sugar decompose or get charred in evaporation to dryness. Also impurities are not removed in this method. However, all these drawbacks are overcome in crystallization.

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

What are the characteristics of the solvent used during purification of copper sulphate by crystallization?

  1. Not dissolve the substance at room temperature

  2. Dissolve the impurities at room temperature

  3. Does not dissolve the impurities at high temperature

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Choosing an appropriate solvent is the important process of crystallisation, as crystallisation works only when a proper solvent is used. It is important to choose a solvent that will not dissolve the substance at room temperature. But as the temperature of the solvent increases, the solubility of the solute also increases. At the same time, the impurities that are present must either be soluble in the solvent at room temperature or must be insoluble in the solvent at a high temperature. If the solvent is not hot when the dissolution is carried out, too much solvent will be used, leading to diminished yield.

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

The principle behind purification by crystallisation is that the :

  1. amount of solute that can be dissolved by a solvent increases with temperature

  2. amount of solute that can be dissolved by a solvent decreases with increase in temperature

  3. both a and b

  4. none of above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Crystallisation is one of the very important purification techniques, purifying substances by removing unwanted by-products. Crystalline compounds are generally purified via this crystallisation process. The principle behind the crystallisation is that the amount of solute that can be dissolved by a solvent increases with temperature.

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

During concentration (saturation), copper sulfate solution is constantly stirred to :

  1. ensure uniform evaporation

  2. prevent formation of a solid crust

  3. both a and b

  4. it is not stirred during saturation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

To concentrate the filtrate of impure copper sulphate, the china dish containing filtrate is heated gently with constant stirring. This is done to ensure uniform evaporation and to prevent formation of a solid crust. 

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

Why is dilute sulphuric acid added during crystallization of copper sulphate?

  1. Prevent hydrolysis of copper sulphate

  2. Prevent crystallization of copper sulphate

  3. Enhance formation of large crystals

  4. All of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

To crystallise copper sulphate, it is dissolved in water and a small quantity of dilute sulphuric acid is added to prevent the hydrolysis of copper sulphte. The impurities left behind in the solution are removed by filtration.

Multiple choice chemistry separation of matter crystals and crystallisation filtration and crystallisation other methods of separation

Which of the following can be separated by crystallization?

  1. Copper sulphate

  2. Benzoic acid

  3. Potash alum

  4. All of above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Crystallization is a method of purification by the formation of crystals. 


The above samples can be separated by crystallization by heating the solution and then cooling them to form crystals.

Hence the correct option is D.