Tag: chemistry

Questions Related to chemistry

Separation of crystals of alum from impure sample is carried out through :

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

  1. centrifugation

  2. distillation

  3. crystallisation

  4. none of the above

Show answer
Correct Option: C
Explanation:

Pure solids are removed as crystal from the solution through crystallisation. Crystallisation is used to purify solids, e.g., seperation of crystals of alum from impure samples.

While obtaining pure copper sulphate from an impure sample what will finally be obtained in the china dish?

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

  1. Impurities of the sample are left behind in the china dish

  2. Copper sulphate

  3. Water droplets

  4. Chine dish remains empty

Show answer
Correct Option: B
Explanation:

When crystallisation is performed to obtain pure copper sulphate from an impure sample, finally crystals of copper sulphate is obtained in the chine dish.

Pure $CuSO _4$ can be obtained from an impure sample by :

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

  1. crystallisation

  2. galvanisation

  3. centrifugation

  4. sedimentation

Show answer
Correct Option: A
Explanation:

Crystallisation is a method used to purity solids. Pure $CuSO _4$ in the form of cystals can be obtained from an impure sample by crystallisation.

Why crystallisation is used as a method of obtaining pure $CuSO _4$ from impure sample?

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

  1. Because $CuSO _4$ is a liquid

  2. Because $CuSO _4$ is a solid

  3. Because $CuSO _4$ is a gas

  4. None of the above

Show answer
Correct Option: B
Explanation:

Crystallisation is a method used to purify solids. $CuSO _4$ is solid, hence it can be obtained as in a pure cystal form from impure samples using cystallisation.

Crystallization is used to separate :

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

  1. solid from solid

  2. liquid from solid

  3. solid from liquid

  4. all of above

Show answer
Correct Option: C
Explanation:

Crystallisation is a sophisticated form of evaporation technique in which crystals of the solute are encouraged to develop during the process of dissolving out from the solution as the solvent evaporates.

X is a solid. Y is a liquid. How can X be separated from a solution of Y?

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

  1. Sedimentation

  2. Filtration

  3. Crystallization

  4. All of above

Show answer
Correct Option: D
Explanation:

Sedimentation is the process of separating an insoluble solid from a liquid in which it is suspended by allowing it to settle to the bottom of the container. Filtration is used for separating insoluble solids from a liquid. Crystallisation is a sophisticated form of evaporation technique in which crystals of the solute are encouraged to develop during the process of dissolving out from the solution as the solvent evaporates.

The copper sulphate solution is heated gently on a water bath for :

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

  1. proper mixing of the sample

  2. evaporation of water

  3. dissolving the copper sulphate in solution

  4. all of above

Show answer
Correct Option: B
Explanation:

Pure copper sulphate is obtained from an impure sample by re-crystallization. The sample is mixed in water and filtered to remove impurities. It is then heated gently on a water bath for evaporation of water. Thus, a saturated solution is obtained.

While obtaining pure copper sulphate by crystallization, the solution is saturated is indicated by :

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

  1. change in color

  2. change in consistency

  3. formation of bubbles

  4. formation of crystals near rod

Show answer
Correct Option: D
Explanation:

During purification of copper sulphate by crystallization, the impure sample is mixed with water and then heated to saturation. The saturation is indicated by dipping glass rod in solution from time to time. Small crystals are formed near the glass rods which indicates saturation.

To crystallize copper sulphate, it is dissolved in water and a small quantity of ................. is also added.

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

  1. concentrated nitric acid

  2. dilute hydrochloric acid

  3. dilute sulphuric acid

  4. dilute nitric acid

Show answer
Correct Option: C
Explanation:

To crystallise copper sulphate, water is dissolved 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.

During crystallization of copper sulphate, heating is stopped when :

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

  1. solution becomes saturated

  2. solution reaches boiling point

  3. solution is reduced to half of its quantity

  4. the solution is not heated at all

Show answer
Correct Option: A
Explanation:

Crystallization process begins with dissolving the impure copper sulphate sample in water and then heating it. It is heated to saturation rather than dryness and once it is saturated the heating is stopped and the solution is allowed to cool.