Tag: chemistry

Questions Related to chemistry

Crystallisation is an example of chemical change.

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

  1. True

  2. False

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Correct Option: B
Explanation:

Crystallization is a process of formation of solid crystals in a homogenous solution. Thus it is a physical process and not a chemical process.

The forbidden gap in germanium crystal is

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

  1. 0.7 eV

  2. $1.12X10^{19} J$

  3. Both 1 and 2

  4. $1.1eV$

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Correct Option: A
Explanation:

The energy difference between the valance and conduction band is called Forbidden energy gap$.$

The forbidden gap in germanium crystal is $0.7 eV$
Hence$,$ o[ption $(A)$ is correct$.$

Which of the following is not a feature of chemical change?


(I) Original substance can be obtained by simple physical methods.
(II) It is a temporary change.
(III) The new substances formed have properties different from those of the reacting substances.

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

  1. I, II

  2. I, III

  3. II, III

  4. All of the above

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Correct Option: A
Explanation:

One more new substances one formed in a chemical change. The new substances formed have properties different from those of the reacting substances. A chemical change is always accompanied by the absorption or evolution of energy in the form of heat, light or sound.

Sun tanning is a/an :

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

  1. physical change

  2. chemical change

  3. both a and b

  4. intermediate

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Correct Option: B
Explanation:

Sun tanning is a chemical change as vitamin D and melanin are produced during tanning. As new products are formed during sun tanning, it is considered to be a chemical change.

Which factor when increased will cause an uncatalyzed reaction to proceed more quickly?

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

  1. Exothermic

  2. Particle Size

  3. Endothermic

  4. Catalyst

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Correct Option: A
Explanation:

Exothermic reactions are usually uncatalyzed and spontaneous. They are chemical reactions that release energy by light or heat. Energy is emitted out.

One of most common solvent used for crystallization is:

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

  1. syrup

  2. normal saline

  3. water

  4. sulphuric acid

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Correct Option: C
Explanation:

One of the most common solvents is water. It is also called as a universal solvent.

Crystallization is the process of formation of crystals. Since water can be easily added or removed from the system. It is the most common for eg. ${ CuSO } _{ 4 }.5{ H } _{ 2 }O$
                                     ${ Fe } _{ 2 }{ O } _{ 3 }.n{ H } _{ 2 }O$

The process of obtaining salt by evaporation of seawater is known as :

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

  1. crystallisation

  2. sedimentation

  3. galvanization

  4. amalgamation

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Correct Option: A
Explanation:

It is known as crystallization - because salt is obtained in crystal form.

Sedimentation is depositing solid as sediment
Galvanization - is the process of protecting iron/metal by a coating of zinc.
Amalgamation - is the formation of amalgam (an alloy of mercury with another metal).

Crystalisation takes place by the process of :

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

  1. evaporation

  2. condensation

  3. sublimation

  4. liquefication

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Correct Option: A
Explanation:

Crystalisation takes place by the process of vaporization.

Crystals are formed by ions, atoms, and molecules having an internal pattern that is ___________ and ___________.

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

  1. irregular, non-repeating

  2. regular, repeating

  3. regular, non-repeating

  4. none of the above

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Correct Option: B
Explanation:

In crystalline solids, the atoms, ions or molecules are arranged in an ordered and symmetrical pattern that is repeated over the entire crystal. The smallest repeating structure of a solid is called a unit cell, which is periodically repeated in three dimensions on a lattice.

Which of the following is the most common solvent used for crystallization?

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

  1. Organic solvent benzene

  2. Plain water

  3. A salt solution of water

  4. Dilute solution of sulphuric acid

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Correct Option: B
Explanation:

The most common solvent used in crystallization is water, it does not dissolve the substance to be purified at room temperature, but it dissolves it well at solvent's boiling point, and dissolves soluble impurities well at room temperature.
Water is capable of dissolving a variety of different substances than any other liquid and is called the universal solvent.