Chapter 4 - Chemical Bonding and Molecular Structure

Which of the following statements is correct?
(i) In the formation of dioxygen from oxygen atoms 10 molecular orbitals
will be formed.
(ii) All the molecular orbitals in the dioxygen will be completely filled.
(iii) Total number of bonding molecular orbitals will not be same as total
number of anti bonding orbitals in dioxygen.
(iv) Number of filled bonding orbitals will be same as number of filled anti
bonding orbitals.

Assertion (A): Among the two O–H bonds in H2O molecule, the energy
required to break the first O–H bond and the other O–H bond
is the same.
Reason (R) : This is because the electronic environment around oxygen is
the same even after breakage of one O–H bond.
(i) A and R both are correct, and R is correct explanation of A.
(ii) A and R both are correct, but R is not the correct explanation of A.
(iii) A is true but R is false.
(iv) A and R both are false.

Assertion (A) : Though the central atom of both NH3 and H2O molecules are
sp3 hybridised, yet H–N–H bond angle is greater than that of
H–O–H.
Reason (R) : This is because nitrogen atom has one lone pair and oxygen
atom has two lone pairs.
(i) A and R both are correct, and R is the correct explanation of A.
(ii) A and R both are correct, but R is not the correct explanation of A.
(iii) A is true but R is false.
(iv) A and R both are false.

In the following questions a statement of Assertion (A) followed by a statement of
Reason (R) is given. Choose the correct option out of the choices given below each
question.

 Assertion (A) : Sodium chloride formed by the action of chlorine gas on
sodium metal is a stable compound.
Reason (R) : This is because sodium and chloride ions acquire octet in
sodium chloride formation.
www.tiwariacademy.com
Exemplar Problems, Chemistry 48
(i) A and R both are correct, and R is the correct explanation of A.
(ii) A and R both are correct, but R is not the correct explanation of A.
(iii) A is true but R is false.
(iv) A and R both are false.

NH ₃ has higher boiling point than PH₃ . Give reason.

What are the types of H-bonding? Which of them is stronger?

Define hydrogen bonding 

Define bond order.

He₂does not exist. Explain in terms of LCAO

Why are bonding molecular orbitals more stable than antibonding molecular
orbitals?

Which one

O₂ and O^2-₂ , - may exhibit paramagnetism?

Explain diagrammatically the formation of molecular orbital by LCAO.

Define antibonding molecular orbital.

Define bonding molecular orbital.

Out of p-orbital and sp-hybrid orbital which has greater directional character
and Why?

What type of hybridisation takes place in (i) p in PCL₅ and (ii) S in S F₆?

In H₂O, H₂S, H₂Se, H₂Te, the bond angle decreases though all have the same bent

shape. Why?

Ethylene is a planar molecule whereas acetylene is a linear molecule. Give
reason.

What is the state of hybridization of carbon atoms in diamond and graphite?

State the hybrid orbitals associated with B in BCl₃ and C in C₂H₄

Describe the shape of sp, sp2 and sp3 hybrid orbital? 

What are the important consolations for hybridisation? 

Give the features of hybridisation. 

Define hybridisation. 

What is zero over lap?

How do covalent bonds form due to orbital overlapping?

What type of bond are formed due to orbital overlap?

What are the different types of s - bond formation?

What type of bond exists in multiple bond (double / triple)?

How many s - and p - bonds are there in a molecule of CH₂ = CH – CH = CH₂ ?

How many s – and p - bond are there in a molecule of C₂H₄ (ethane )? 

Why is s– bond stronger than p - bond?

What is pi – bond?

What is sigma bond?

S – orbital does not show any preference for direction. Why? 

How is VBT different from Lewis concept? 

In SF4 molecule, the lp electrons occupies an equatorial position in the trigonal

bipyramidal arrangement to an axial position. Give reason

How would you attribute the structure of PH3 molecule using VSEPR model? 

Why does H2O have bent structure? 

CO2 is linear whereas SO2 is bend – shaped. Give reason

. What’s difference between lone pair and bonded pair of electrons? 

Give the main features of VSEPR Theory

Dipole moment of Be F2 is zero. Give reason. 

On which factor does dipole moment depend in case of polyatomic

molecules.

Draw the resonating structure of NO3

Write the resonating structure of O3 molecule. 

Why is BF3 non – polar? 

Why is dipole moment of CO2, BF3, CCl4 is zero? 

Why NH3 has high dipole moment than NF3 though both are pyramidal? 

Dipole moment is a scalar or a vector quantity?

Give the mathematical expression of dipole moment

 Define dipole moment

Define covalent radius.

Out of covalent and hydrogen bonds, which is stronger.

What type of bond is formed when atoms have high difference of
electornegativity?

. How would the bond lengths vary in the following species? C₂, C₂

- C²₂

Give reason why H₂

+ ions are more stable than H₂

- though they have the same

bond order.

Define bond order.

Which one of the following has the highest bond order? N₂, N₂

+ or N₂

-.

Mention the factors that influence the formation of an Ionic bond.

What changes are observed in atoms undergoing ionic bonding?

Define an ionic bonding.

Give the Lewis dot structure of HNO3

Write the Lewis structure for CO molecule

Write the significance of octet rule.

Give the octet rule in short.

Define electrovalent bond.

How can you explain the formation of NaCl according to kossel concept?

Give the main feature of Kossel’s explanation of chemical bonding.

Write electron dot structure (Lewis structure) of Na, Ca, B, Br, Xe, As, Ge, N3-.

Give the main feature of Lewis approach of chemical bonding.

Define a chemical bond.

Define hydrogen bond. Is it weaker or stronger than the van der Waals forces?

Describe the hybridisation in case of PCl₅. Why are the axial bonds longer as compared to equatorial bonds?

Write the significance of a plus and a minus sign shown in representing the orbitals.

Compare the relative stability of the following species and indicate theirmagnetic properties;

O2,,(superoxide), (peroxide)

Use molecular orbital theory to explain why the Be₂molecule does not exist.

Write the important conditions required for the linear combination of atomic orbitals to form molecular orbitals.

Explain the formation of H₂molecule on the basis of valence bond theory.

Distinguish between a sigma and a pi bond.

What do you understand by bond pairs and lone pairs of electrons? Illustrate by giving one example of each type.

Which hybrid orbitals are used by carbon atoms in the following molecules?

CH₃-CH₃; (b) CH₃-CH=CH₂; (c) CH₃-CH₂-OH; (d) CH₃-CHO (e) CH₃COOH

Considering x-axis as the internuclear axis which out of the following will notform a sigma bond and why? (a) 1s and 1s (b) 1s and 2p_x(c) 2p_yand 2p_y(d) 1s and 2s.

What is the total number of sigma and pi bonds in the following molecules?

(a) C₂H₂(b) C₂H₄

Draw diagrams showing the formation of a double bond and a triple bond between carbon atoms in C₂H₄and C₂H₂molecules.

Is there any change in the hybridisation of B and N atoms as a result of the following reaction?

BF₃+ NH₃ → F₃B.NH₃

What is meant by hybridisation of atomic orbitals? Describe the shapes of sp, sp², sp³hybrid orbitals.

Which out of NH₃and NF₃has higher dipole moment and why?

Explain why BeH₂molecule has a zero dipole moment although the Be-H bonds are polar.

Apart from tetrahedral geometry, another possible geometry for CH₄is square planar with the four H atoms at the corners of the square and the C atom at its centre. Explain why CH₄is not square planar?

The skeletal structure of CH3COOH as shown below is correct, but some of the bonds are shown incorrectly. Write the correct Lewis structure for acetic acid.

Arrange the bonds in order of increasing ionic character in the molecules: LiF, K₂O, N₂, SO₂and ClF₃.

Explain with the help of suitable example polar covalent bond.

Define electronegativity. How does it differ from electron gain enthalpy?

Write the significance/applications of dipole moment.

Although both CO₂and H₂O are triatomic molecules, the shape of H₂O molecule is bent while that of CO₂is linear. Explain this on the basis of dipole moment.

Use Lewis symbols to show electron transfer between the following atoms to form cations and anions: (a) K and S (b) Ca and O (c) Al and N.

H3PO3can be represented by structures 1 and 2 shown below. Can these two structures be taken as the canonical forms of the resonance hybrid representing H3PO3? If not, give reasons for the same.

Define the bond length.

How do you express the bond strength in terms of bond order?

Although geometries of NH₃and H₂O molecules are distorted tetrahedral, bond angle in water is less than that of ammonia. Discuss.

Discuss the shape of the following molecules using the VSEPR model:

BeCl₂, BCl₃, SiCl₄, AsF₅, H₂S, PH₃

Write the favourable factors for the formation of ionic bond.

Define octet rule. Write its significance and limitations.

Draw the Lewis structures for the following molecules and ions:

H₂S, SiCl₄, BeF₂,, HCOOH

Write Lewis symbols for the following atoms and ions:

S and S^2-; Al and Al³⁺; H and H^-

Write Lewis dot symbols for atoms of the following elements: Mg, Na, B, O, N, Br.

Explain the formation of a chemical bond.