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Properties of covalent compounds - class-XI

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Which statement about bonding is not correct?

  1. Carbon can form four single covalent bonds

  2. Chlorine atoms react to gain a noble gas electronic structure

  3. Covalent bonding involves losing and gaining electrons

  4. Hydrogen molecules have the formula $H _{2}$


Correct Option: C
Explanation:


Solution:- (C) Covalent bonding involves losing and gaining electrons

Covalent bonding involves sharing of electrons while the losing and gaining of electrons is found in ionic bonding.

Covalent bonds are formed when electrons are $1$ .
Most covalent compounds have $2$ electrical conductivity.
Which words correctly complete gaps $1$ and $2$?

  1. Shared - high

  2. Shared - low

  3. Transferred - high

  4. Transferred - low


Correct Option: B
Explanation:

Solution:- (B) Shared - low

  1. Covalent bonds are formed by sharing of electrons.
  2. Most covalent compounds have low electrical conductivity due to low mobility, i.e., no free electrons.

Compound $X$ consists of molecules.
In the liquid state X will

  1. becomes ionic

  2. be an electrolyte but not conduct electricity.

  3. conduct electricity only

  4. not conduct electricity

  5. non of the above


Correct Option: D
Explanation:

Compound X consists of molecules, so its covalent compounds and dont have any charged ions to conduct electricity so it will not conduct electricity.

Butane is:

  1. ionic compound

  2. noble gas

  3. polar covalent compound

  4. non-polar covalent compound


Correct Option: D
Explanation:

Butane can be written as $CH _3-CH _2-CH _2-CH _3$. The electronegativities of Carbon and hydrogen are almost same and hence none of them is more electronegative than the other. Thus the compound is non polar in nature, as the electrons are equally distributed on the molecule.

Butane is an organic molecule and the bonds are formed by mutual sharing of electrons between the atoms. Hence, butane is a covalent compound.
Option D is the correct answer.

More covalent character is found in 

  1. $SnCl _4$

  2. $KCl$

  3. $CaCl _2$

  4. $SnCl _2$


Correct Option: A

Covalent bond is present in which of the following molecule?

  1. Sodium Chloride

  2. carbon dioxide

  3. Sodium Bromide

  4. All of these


Correct Option: B
Explanation:

Carbon dioxide $CO _2$ is covalent compound. In this molecule, two non-metals carbon and oxygen share their electrons to form covalent bonding. Remaining all molecules shows formation of ionic bonding.

Compound $X$ is highly volatile and insoluble in water. Bonding in $X$ is :

  1. ionic

  2. covalent

  3. polar covalent

  4. coordinate


Correct Option: B
Explanation:

Like dissolves like. As the compound is volatile and insoluble in water, so compound in non-polar, means it contains covalent bonds.


Hence the correct option is B.

Which of the following is not a property of covalent compounds?

  1. They have low melting points.

  2. They are not electrical conductors.

  3. They exhibit space isomerism.

  4. They undergo chemical reactions quickly.


Correct Option: D
Explanation:

Covalent compounds have low melting points. are non-conductors of electricity, they exhibit space isomerism because covalent bonds are directional. Covalent compounds reactions are slow because breaking of bond is non-spantaneous.

Covalent compounds are soluble in :

  1. polar solvents

  2. non-polar solvents

  3. concentrated acids

  4. all solvents


Correct Option: B
Explanation:

Polar compound are soluble in polar solvents. As covalent compounds are less polar or non-polar, they are soluble in non-polar solvents like ether and ionic compounds are soluble in polar solvents like water $(H _2O)$.

A solid substance is soft, has a low melting point, and is a poor conductor of electricity. It is:

  1. an ionic solid

  2. a network solid

  3. a metallic solid

  4. a covalent solid


Correct Option: D
Explanation:

Covalent solids are soft, have a low melting point (due to relatively weak bonds), and are a poor conductor of electricity (due to absence of free ions).


Option D is correct.

Which of the following is good conductor of electricity?

  1. Diamond

  2. Graphite

  3. Lamp black

  4. Characoal


Correct Option: B
Explanation:

Graphite is an allotrope (a different structural form) of carbon (so is diamond), but unlike diamond, graphite can conduct electricity. The reason is that graphite consists of flat hexagons, all liked together in a flat plane. The carbons in the hexagons have delocalized pi bonding (pi bonds, along with a sigma bond, make up a double bond) which allows electrons to easily move from atom to atom making it a good conductor of electricity.

Which of the following is used as lubricant ?

  1. Graphite

  2. Charcoal

  3. Diamond

  4. Coke


Correct Option: A
Explanation:

Graphite is a mineral made of loosely bonded sheets of carbon atoms, giving it a slippery texture that makes it a very effective lubricant. This slippery quality also makes graphite a good material for pencil lead because it easily sloughs off onto paper.

Covalent compounds have generally low melting and boiling points.

  1. True

  2. False


Correct Option: A
Explanation:

Covalent bond have weak intermolecular forces, that is to say, the forces between molecules is very weak. The consequence of this, is that it becomes easy to move individual molecules away from other molecules as the bonding between molecules is weak, hence it needs little energy to break. Since temperature is proportional to energy, that means the temperature required to melt the compound is low.
Thus option "A" is correct.

Covalent compounds are usually water soluble.

  1. True

  2. False


Correct Option: B
Explanation:

A covalent bond is formed between non metal atoms, which combine together by sharing electrons. covalent compounds have low melting points, do not dissolve in water, and do not conduct an electric current in solution that make them non-polar. 
Thus, Option "B" is correct.

The density of water is more than ice.

  1. True

  2. False


Correct Option: A
Explanation:

The hydrogen bonds in an ice molecule are more apart than those in water molecules. Hence ice is loosely packed and is less densed than water. 

Which of the following is not a characteristic of a covalent compound :-

  1. It has low melting point and boiling point

  2. It is formed between two atoms having no or very small electronegativity difference

  3. They have no definit geometry

  4. They are generally insouble in water


Correct Option: C
Explanation:

 Covalent bonds are directional, meaning that atoms so bonded prefer specific orientations relative to one another, hence they have distinct geometries.

Which of the following statements is not true about covalent compounds:-

  1. They may exhibit space isomersim

  2. They have-low melting and boiling points

  3. They show ionic reaction

  4. They show molecular reaction


Correct Option: C
Explanation:

Covalent compounds do not show ionic reaction. 


Example: Free radical halogenation of alkanes in the presence of sunlight.
Hydrogenation of alkenes.

Which of the following represents the correct increasing order of forces of attraction between the molecules?

  1. Oxygen, Sodium chloride, Mercury, Water, Hydrogen chloride

  2. Oxygen, Hydrogen chloride, Water, Mercury, Sodium chloride

  3. Oxygen, Water, Hydrogen chloride, Mercury, Sodium chloride

  4. Oxygen, Mercury, Water, Hydrogen chloride, Sodium chloride


Correct Option: B
Explanation:

The increasing order of forces of attraction between the molecules can be written as;
$O _{2}$(weak Van der waal forces) < HCl( dipole-dipole interactions) < $H _{2}O$( hydrogen bonding) < Hg( metallic bond) < NaCl (ionic bonding)

A solid which is transparent to visible light and whose conductivity increases with temperature is formed by :

  1. Metallic binding

  2. Ionic binding

  3. Covalent binding

  4. Van der Waals binding


Correct Option: C
Explanation:

A solid which is transparent to visible light and whose conductivity increases with temperature is
formed by covalent bonding, like a semi conductor.

Compounds evaporating easily and giving off a smell are?

  1. Ionic compounds

  2. Covalent bonds

  3. Metallic bonds

  4. Diatic bonds


Correct Option: B
Explanation:

Covalent compounds have negligible forces of attraction and these are gases e.g. $HCl$, sulfur dioxide,carbon dioxide and methane. There are weak forces of attraction and such covalent substances are low boiling temperature liquids such as ethanol so boils rapidly and gives off smell.

The electronic configuration of elements A, B, C, D and E are :
A (2, 8, 7)       B (2, 8, 1)       C (2)          D (2, 6)        E(2, 8)
If elements A & B combine to form a compound then its chemical formula would be _______ .

  1. $BA$

  2. $B _2A$

  3. $2BA$

  4. $BA _2$


Correct Option: A
Explanation:

In the above question element A is equivalent to chlorine& B to sodium thus the structure besides shows the bonding giving rise to $NaCl$ Hence for our eg, it is $BA$.

Covalent compounds are generally _________ in water.

  1. soluble

  2. insoluble

  3. ionized

  4. hydrolysed


Correct Option: B
Explanation:

Ionic compounds are soluble in water whereas covalent compounds are insoluble in water.

Maximum number of bonds between two atoms of a covalent bond can be:

  1. four

  2. three

  3. two

  4. one


Correct Option: B
Explanation:

Covalent bonds between atoms are quite strong, but attractions between molecule/compounds  or intermolecular forces, can be relatively weak. Covalent compounds generally have low boiling and melting points, and are found in all three physical states covalent bonds between atoms are quite strong, but attractions between molecules/compounds or intermolecular forces, can be relatively work. Covalent compounds generally have low boiling and melting points, and are found in all three physical states at room temperature. at room temperature.

Two compounds of A and B have similar formula $AX _3$ and $BX _3$ respectively. But, the compound of A has the dipole moment and dipole moment of the compound of B is zero. Which of the following statements is true regarding compounds of A & B?

  1. A and B are iso structural.

  2. A may have lone pair on central atom whereas B has no lone pair.

  3. A and B differ wrt type of hybridisation of central atom.

  4. All the above.


Correct Option: C
Explanation:

A and B differ wrt type of hybridization of central atom. 'B' may have lone pair on central atom whereas 'A' has no lone pair.
'A' has dipole moment as it is trigonal planar in which individual bond dipoles cancel each other and dipole moment of 'B' is zero as it has pyramidal geometry in which individual bond dipoles do not cancel each other. 

Assertion : $CH _3Cl$ is a polar molecule.
Reason : The Lewis diagram of polar molecules always has at least one lone pair of electrons.

  1. Assertion and Reason  are correct and Reason  is the correct explanation of Assertion 

  2. Both the Assertion and Reason are correct and Reason  is not the correct explanation of Assertion 

  3. Assertion is correct but Reason is not correct

  4. Assertion is not correct but Reason is correct

  5. Both the Assertion and Reason are not correct


Correct Option: C
Explanation:

Compound in statement 1 must be $C{ H } _{ 3 }Cl$.Since carbon,hydrogen and chlorine have different electronegativity,the bonds are polar in nature. Moreover, there is symmetry in the structure of the molecule, so there is a net dipole moment hence it is a polar molecule.

It is not a necessary condition that there has to at least one lone pair of electrons for a molecule to be polar. $C{ H } _{ 3 }Cl$ is an example.

Which of the following statements is/are true?

  1. Covalent bonds are directional.

  2. Ionic bonds are non-directional.

  3. A polar bond is formed between two atoms which have the same electronegativity value.

  4. The presence of polar bonds in a polyatomic molecule suggests that it has zero dipole moment.


Correct Option: A,B
Explanation:

Covalent bonds are directional and ionic bonds are nondirectional. A polar bond is formed between two atoms which have different electronegativity value. The presence of polar bonds in a polyatomic molecule suggests that mostly it has non-zero dipole moment.

$A,\ B,\ C$ are three substances. $A$ does not conduct electricity in the solid, molten state and aqueous solution. $B$ conducts electricity both in the fused and aqueous states, while $C$ conducts electricity only in the aqueous state. In solid state neither $B$ nor $C$ conducts electricity. Which of the following statements is/are true regarding $A,\ B$ and $C $?

  1. $A$ has polar covalent linkage

  2. $A$ has non-polar covalent linkage

  3. $B$ is ionic in nature

  4. Cation has polar covalent bonds


Correct Option: B,C,D
Explanation:
$A$ does not conduct electricity in the solid and molten state suggests that $A$ is not an ionic compound and it can be a covalent compound.
$A$ is not conducting electricity in aqueous solution also, it suggests that all the element in compound $A$ has the same electronegativity.
Hence, $A$ can be non-polar covalent compound that means it has non-polar covalent linkage.
$B$ conducts electricity in a fused state and in aqueous states, This represents that the electronegativity difference in the compound is very high.
Hence, $B$ can be an ionic bond
$C$ conducts electricity in only in the aqueous state. It means that $C$ does not conduct electricity in a molten state that means $C$ is not an ionic compound.
It can be a covalent compound and as it is conducting electricity in the aqueous state, there must be small electronegativity difference.
Hence, $C$ can be a polar covalent compound.
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