Tag: crystallisation

Questions Related to crystallisation

Which of the following represents correct statement(s)?

chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. Salt can be obtained by the evaporation of sea water.

  2. The salt obtained during crystallisation is pure and its crystals are large.

  3. After crystallisation, the shape of the crystals can be seen clearly.

  4. Large crystals of pure substances cannot be formed from their solutions.

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Correct Option: A
Explanation:

The option (A) represents correct statements.
Salt can be obtained by the evaporation of sea water.
The salt obtained during crystallisation is not pure and its crystals are small.
After crystallisation, the shape of the crystals cannot be seen clearly.
Large crystals of pure substances can be formed from their solutions.

Salt can be obtained by ___________ of sea water.

chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. sublimation

  2. cooling

  3. evaporation

  4. heating

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Correct Option: C
Explanation:

On evaporation of seawater in shallow pools, salt along with impurities remain behind. Impured salt is taken in a tank and its saturated solution is prepared. In a saturated solution of salt, HCl vapours are passed. Chloride ions being common to both, it's concentration increases, and NaCl gets precipitated which is free from impurities.

The process of forming large crystals of pure substances from their solutions is known as __________.

chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. evaporation

  2. purification

  3. condensation

  4. crystallisation

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Correct Option: D
Explanation:

The process of forming large crystals of pure substances from their solutions is known as Crystallization. The principle of crystallization is concerned with the thermodynamic conditions of crystallization and the kinetics of crystal nucleation and growth.
Crystallization is the physical transformation of a liquid solution or gas to a crystal which is a solid with an ordered internal arrangement of molecules, ions or atoms.

Crystallisation is an example of ____________.

chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. physical change

  2. biological change

  3. chemical change

  4. fundamental change

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Correct Option: A
Explanation:

The process of formation of solid crystals from a homogeneous solution is called crystallization. It is a physical change. Crystallization is the solidification of atoms or molecules into a highly structured form called a crystal. It can also refer to the solid-liquid separation and purification technique in which mass transfer occurs from a liquid solution to a pure solid crystalline phase.

For example Salt we get from seawater can have many impurities in it. To remove these impurities, the process of crystallization is used.

Hence, the correct option is $A$

A synthetic indicator phenolphthalein gives _____ colour in acidic solution.

chemistry changes around us crystallisation process of separating components of a mixture physical changes

  1. red

  2. blue

  3. pink

  4. colourless

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Correct Option: D
Explanation:

Phenolphthalein [3,3-Bis (4- hydroxyphenyl)- 2 benzofuran- 1-one] is often used as an indicator in acid-base titrations. It turns colourless in acidic solutions and pink in basic solutions. Phenolphthalein is slightly soluble in water and usually dissolved in alcohols for use in experiments. It is a weak acid which can loose $H^{+}$ ions in solution.