Tag: chemistry

Questions Related to chemistry

Which of the following exists as covalent crystals in the solid state?
chemistry solid state classification of crystalline solids classification of solids introduction to solids

  1. Sulphur

  2. Phosphorous

  3. Iodine

  4. Silicon

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Correct Option: D
Explanation:

Covalent crystals are formed by sharing of valence electrons between two atoms resulting in the formation of a covalent bond. 


The covalent bonds extend in two or three dimensions forming a giant interlocking structure called network. Diamond and graphite are the good examples of this type
.
Silicon $(Si)$: Covalent solid
Sulphur $(S _8)$: Molecular solid
Phosphorus $(P _4)$ : Molecular solid
Iodine $(I _2)$ : Molecular solid

Network solid among the following is :

chemistry solid state classification of crystalline solids classification of solids introduction to solids

  1. $Li _{2}O$

  2. $SiO _{2}$

  3. $H _{2}O$

  4. $CO _{2}$

  5. $NaCl$

Show answer
Correct Option: B
Explanation:

A network solid or covalent network solid is a chemical compound (or element) in which the atoms are bonded by covalent bonds in a continuous network extending throughout the material. In a network solid there are no individual molecules, and the entire crystal may be considered a macromolecule. $SiO _2$ is a network solid. $Li _2O$ and $NaCl$ are ionic crystals. $H _2O$ is a covalent liquid and $CO _2$ is a covalent gas.

Which of the following molecules has polar bonds but is a nonpolar molecule?

chemistry solid state classification of crystalline solids classification of solids introduction to solids

  1. $H _{2}$

  2. $H _{2}O$

  3. $NH _{3}$

  4. $NaCl$

  5. $CO _{2}$

Show answer
Correct Option: E
Explanation:

Carbon dioxide $\displaystyle CO _2 $ has polar bonds but is a nonpolar molecule. The structure of $\displaystyle  CO _2$  is linear. The individual bond dipoles cancel each other as they point in opposite direction and are equal in magnitude. Hence, the molecule is non polar with zero dipole moment.

$Li (s) $ is:

chemistry solid state classification of crystalline solids classification of solids introduction to solids

  1. an ionic substance

  2. a polar covalent substance

  3. a nonpolar covalent substance

  4. an amorphous substance

  5. a metallic network

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Correct Option: E
Explanation:

$Li (s)$ is a metallic solid and has metallic network involving strong metallic bonds. It is crystalline solid formed by atoms of $Li$ metal.

A diamond is an example of this type of solid.

chemistry solid state classification of crystalline solids classification of solids introduction to solids

  1. Amorphous solid

  2. Ionic solid

  3. Metallic solid

  4. Network covalent solid

Show answer
Correct Option: D
Explanation:

Covalent-network (also called atomic) solids—Made up of atoms connected by covalent bonds; the intermolecular forces are covalent bonds as well. Characterized as being very hard with very high melting points and being poor conductors. Examples of this type of solid are diamond and graphite, and the fullerenes. 

In the ionic solid $NH _4NO _3$, ions present are:

chemistry solid state classification of crystalline solids classification of solids introduction to solids

  1. $NH _4^+$   and $NO^- _3$

  2. $N^{5+}, H^+$ and $O^{2-}$

  3. $NH _4^-, N^{5+}$ and $O^{2-}$

  4. $NH _3, H^+$   and $NO _3^-$

  5. $N^{5+}, N^{3-}, H^+$ and $O^{2-}$

Show answer
Correct Option: A
Explanation:

In the ionic solid ammonium nitrate $NH _4NO _3$,  ions present are ammonium $NH _4^+$   and nitrate $NO^- _3$. Strong electrostatic force of attraction is present between oppositely charged ions.

Salts are the example of:

chemistry solid state classification of crystalline solids classification of solids introduction to solids

  1. Amorphous solid

  2. Ionic solid

  3. Metallic solid

  4. Molecular solid

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Correct Option: B

$I$. Ionic solids have high melting points.
$II$. Molten ionic solids conduct electricity.

chemistry solid state classification of crystalline solids classification of solids introduction to solids

  1. Statement $I$ is true, Statement $II$ is true

  2. Statement $I$ is true, Statement $II$ is false

  3. Statement $I$ is false, Statement $II$ is true

  4. Statement $I$ is false, Statement $II$ is false

Show answer
Correct Option: A
Explanation:

Ionic solids are composed of oppositely charged ions(i.e. positively charged cations and negatively charged anions). There is a strong force of attraction because they are oppositely charged. Hence a lot of energy is required to break them due to which they have high melting point.

In molten state, ions are free to move and hence can conduct electricity. That's why molten ionic solid can conduct electricity.

Which type of bonding is responsible for the ability of some solid materials to conduct electricity?

chemistry solid state classification of crystalline solids classification of solids introduction to solids

  1. Ionic Bonding

  2. Metallic Bonding

  3. Hydrogen Bonding

  4. Covalent Bonding

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Correct Option: B
Explanation:

Metallic bonding is responsible for the stability of some solid material to conduct electricity. These bonding have delocalized electrons which act as charge carriers and hence conduct electricity.

Which type of bond does not allow a solid to conduct electricity but will conduct when the substance is in the molten state?

chemistry solid state classification of crystalline solids classification of solids introduction to solids

  1. Ionic Bonding

  2. Metallic Bonding

  3. Dipole-Dipole

  4. Hydrogen Bonding

Show answer
Correct Option: A
Explanation:

In the solid-state ionic compounds are held together by strong electrostatic forces. So, the conduction of electricity is not possible. But in the molten state, the ions are free to move and hence conduct electricity.