Tag: chemistry

Questions Related to chemistry

The number of free electrons in the outermost shell of carbon in graphite is:

chemistry the world of carbon organic compounds allotropes of carbon versatile nature of carbon

  1. four

  2. one

  3. two

  4. three

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Correct Option: B
Explanation:

The number of free electrons in the outermost shell of carbon in graphite is one. Each $\displaystyle C$ atom is $\displaystyle sp^2$ hybridised. Each $\displaystyle C$ atom forms 3 covalent bonds with 3 other $\displaystyle C$ atoms. Thus, each $\displaystyle C$ atom has one electron in unhybridized $\displaystyle 2p$ orbital which it uses for $\displaystyle \pi $ bonding.

Select the correct statement.

chemistry the world of carbon organic compounds allotropes of carbon versatile nature of carbon

  1. Carbon-carbon bond order in graphite is more than diamond

  2. Carbon-carbon bond order in graphite is less than diamond

  3. Hybridization of each carbon in diamond is ${sp}^{2}$

  4. Hybridization of each carbon in graphite is ${sp}^{3}$

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Correct Option: A
Explanation:

Hybridization of carbon is $sp^2$ in graphite as $1$ carbon atom is joined to $3$ other carbon atoms. In diamond, the hybridization is $sp^3$ as $1$ carbon atom is joined to $4$ other carbon atoms.

Bond order= $\cfrac {\text {Total number of valence electrons of carbon}}{\text {number of }\sigma\text { bonds}}$
For graphite, $B.O= \cfrac {4}{3}= 1.33$,
For diamond, $B.O= \cfrac {4}{4}=1$ .
Hence, Bond order for graphite is more than that for diamond.

Which of the following statements is/are correct?


(1) Graphite is used in making electrodes because it can conduct electricity.
(2) Graphite is used as a solid lubricant.
(3) Graphite is used in the manufacture of crucibles.
(4) Graphite is also known as black lead.

chemistry the world of carbon organic compounds allotropes of carbon versatile nature of carbon

  1. 1 and 4

  2. 2 and 3

  3. 1 and 2

  4. All of them

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Correct Option: D
The phenomenon of existence of an element in more than one physical form is called allotropy.
chemistry carbon and its compounds organic compounds allotropes of carbon versatile nature of carbon

  1. True

  2. False

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Correct Option: A
Explanation:

Allotropy or allotropism is the property of some chemical elements to exist in two or more different forms, known as allotropes of these elements.

Example : Graphite and diamond

Tap water is:

chemistry composition of matter classification of mixtures mixtures: examples and properties types of solutions

  1. compound

  2. a mixture

  3. an element

  4. none of these

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Correct Option: B
Explanation:

Tap water is not the pure form of water, it contains a large number of salts, elements, bacteria and other impurities,

so, tap water is considered as a mixture.

Identify the mixture from the following:

chemistry separation of substances classification of mixtures mixtures: examples and properties types of solutions

  1. Oxygen

  2. Carbon dioxide

  3. Hydrogen

  4. Air

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Correct Option: D
Explanation:

The mixture consists of constituents in indefinite proportion. It may change over time. Air has 78% Nitrogen, 21% Oxygen and 1% other constituents such as $CO _2$, water vapour etc. About 100 years ago the proportion of $CO _2$ in the air was about 0.029% and now it is 0.035%. Thus we see that it's proportion has changed.

Which of the following is a mixture?

chemistry separation of substances classification of mixtures mixtures: examples and properties types of solutions

  1. Water

  2. Oxygen

  3. Carbon dioxide

  4. Air

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Correct Option: D
Explanation:

A mixture consists of constituents in indefinite proportion. It may change over time. Air has 78% Nitrogen, 21% Oxygen and 1% other constituents such as CO2, water vapour etc. About 100 years ago proportion of CO2 in air was about 0.029% and now it is 0.035%. Thus we see that it's proportion has changed. Therefore, air is a mixture.

A substance that cannot be separated into other kinds of matter by any physical process is known as :

chemistry separation of substances classification of mixtures mixtures: examples and properties types of solutions

  1. element

  2. compound

  3. solution

  4. mixture

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Correct Option: A
Explanation:

Elements are the fundamental particles of all kinds of matter. They can't be separated by any physical or chemical means.

Which of the following is not a property of a mixture?

chemistry separation of substances classification of mixtures mixtures: examples and properties types of solutions

  1. Mixtures have definite set of properties

  2. Components in mixture retain their original properties

  3. The parts of mixture can be separated by physical means

  4. Mixtures do not have a sharp melting or boiling point

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Correct Option: A
Explanation:

The important point regarding mixture is that it always retain the original property of its components, so mixture dont have any definite set of properties.

Which of the following is an example of mixture in which various constituents are mixed uniformly?

chemistry separation of substances classification of mixtures mixtures: examples and properties types of solutions

  1. Solution of salt in water

  2. Air

  3. Alloy

  4. All of the above

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Correct Option: D
Explanation:

Solution of salt in water, air, alloy are all examples of homogeneous mixture. They are formed by mixing different elements in to form a mixture which is in single state. Hence they are also called as homogeneous mixture.