Solution of Chapter 4. Chemical Bonding and Molecular Structure (Chemistry - Exemplar Book)

Isostructural species are those which have the same shape and hybridisation. Among the given species identify the isostructural pairs.

Polarity in a molecule and hence the dipole moment depends primarily on the electronegativity of the constituent atoms and shape of a molecule. Which of the following has the highest dipole moment?

The types of hybrid orbitals of nitrogen in NO₂⁺ , NO₃^- and NH₄⁺ respectively are expected to be

Hydrogen bonds are formed in many compounds e.g., H₂O, HF, NH₃ . The boiling point of such compounds depends to a large extent on the strength of hydrogen bond and the number of hydrogen bonds. The correct decreasing order of the boiling points of above compounds is :

In PO₄^3- ion the formal charge on the oxygen atom of P–O bond is

In NO₃^- ion, the number of bond pairs and lone pairs of electrons on nitrogen atom are

Which of the following species has tetrahedral geometry?

Number of π bonds and σ bonds in the following structure is–

Which molecule/ion out of the following does not contain unpaired electrons?

In which of the following molecule/ion all the bonds are not equal?

In which of the following substances will hydrogen bond be strongest?

If the electronic configuration of an element is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s², the four electrons involved in chemical bond formation will be_____.

Which of the following angle corresponds to sp² hybridisation?

The electronic configurations of three elements, A, B and C are given below. Answer the questions 14 to 17 on the basis of these configurations.

A 1s² 2s² 2p⁶

B 1s² 2s² 2p⁶ 3s² 3p³

C 1s² 2s² 2p⁶ 3s² 3p⁵

Stable form of A may be represented by the formula :

Stable form of C may be represented by the formula :

The molecular formula of the compound formed from B and C will be

The bond between B and C will be

Which of the following order of energies of molecular orbitals of N2 is correct?

Which of the following statement is not correct from the view point of molecular orbital theory?

Which of the following options represents the correct bond order :

The electronic configuration of the outer most shell of the most electronegative element is

Amongst the following elements whose electronic configurations are given below, the one having the highest ionisation enthalpy is

In the following questions two or more options may be correct.

Which of the following have identical bond order?

In the following questions two or more options may be correct.

Which of the following attain the linear structure:

In the following questions two or more options may be correct.

CO is isoelectronic with

In the following questions two or more options may be correct.

Which of the following species have the same shape?

In the following questions two or more options may be correct.

Which of the following statements are correct about CO₃^2- ?

In the following questions two or more options may be correct.

Diamagnetic species are those which contain no unpaired electrons. Which among the following are dimagnetic?

In the following questions two or more options may be correct.

Species having same bond order are :

In the following questions two or more options may be correct.

Which of the following statements are not correct?

Explain the non linear shape of H₂ S and non planar shape of PCl3 using valence shell electron pair repulsion theory.

Using molecular orbital theory, compare the bond energy and magnetic character of O⁺₂ and O^-₂ species.

Explain the shape of BrF₅.

Structures of molecules of two compounds are given below :

(a) Which of the two compounds will have intermolecular hydrogen bonding and which compound is expected to show intramolecular hydrogen bonding.

(b) The melting point of a compound depends on, among other things, the extent of hydrogen bonding. On this basis explain which of the above two compounds will show higher melting point.

(c) Solubility of compounds in water depends on power to form hydrogen bonds with water. Which of the above compounds will form hydrogen bond with water easily and be more soluble in it.

Why does type of overlap given in the following figure not result in bond formation?

Explain why PCl₅ is trigonal bipyramidal whereas IF₅ is square pyramidal.

In both water and dimethyl ether (CH₃ —Ο — CH₃ ), oxygen atom is central atom, and has the same hybridisation, yet they have different bond angles. Which one has greater bond angle? Give reason.

Write Lewis structure of the following compounds and show formal charge on each atom.

HNO₀ , NO₂, H₂SO₄ Charge given is wrong

The energy of σ2pz molecular orbital is greater than π2p_x and π2p_y molecular orbitals in nitrogen molecule. Write the complete sequence of energy levels in the increasing order of energy in the molecule. Compare the relative stability and the magnetic behaviour of the following species :

N₂, N₂⁺ , N₂^- , N₂²⁺

What is the effect of the following processes on the bond order in N₂ and O₂?

(i) N₂→ N₂⁺ + e^-

(ii) O₂→ O₂⁺ + e^-

Give reasons for the following :

(i) Covalent bonds are directional bonds while ionic bonds are nondirectional.

(ii) Water molecule has bent structure whereas carbon dioxide molecule is linear.

(iii) Ethyne molecule is linear.

What is an ionic bond? With two suitable examples explain the difference between an ionic and a covalent bond?

Arrange the following bonds in order of increasing ionic character giving reason

N—H, F—H, C—H and O—H

Explain why CO₃^2- ion cannot be represented by a single Lewis structure. How can it be best represented?

Predict the hybridisation of each carbon in the molecule of organic compound given below. Also indicate the total number of sigma and pi bonds in this molecule.

Group the following as linear and non-linear molecules :

H₂O, HOCl, BeCl₂, Cl₂O

Elements X, Y and Z have 4, 5 and 7 valence electrons respectively.

(i) Write the molecular formula of the compounds formed by these elements individually with hydrogen.

(ii) Which of these compounds will have the highest dipole moment?

Draw the resonating structure of

(i) Ozone molecule

(ii) Nitrate ion

Predict the shapes of the following molecules on the basis of hybridisation.

BCl₃, CH₄ , CO₂, NH₃

All the C—O bonds in carbonate ion (CO^2-₃ ) are equal in length. Explain

What is meant by the term average bond enthalpy? Why is there difference in bond enthalpy of O—H bond in ethanol (C₂H₅OH) and water?

Match the species in Column I with the type of hybrid orbitals in Column II.

Match the species in Column I with the geometry/shape in Column II.

Match the species in Column I with the bond order in Column II.

Match the items given in Column I with examples given in Column II.

Match the shape of molecules in Column I with the type of hybridisation in Column II.

In the following question 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.

(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 question 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) : 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 question 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): 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.

(i) Discuss the significance/ applications of dipole moment.

(ii) Represent diagrammatically the bond moments and the resultant dipole moment in CO₂ , NF₃ and CHCl₃.

Use the molecular orbital energy level diagram to show that N2 would be expected to have a triple bond, F2, a single bond and Ne2, no bond.

Briefly describe the valence bond theory of covalent bond formation by taking an example of hydrogen. How can you interpret energy changes taking place in the formation of dihydrogen?

Describe hybridisation in the case of PCl₅ and SF₆. The axial bonds are longer as compared to equatorial bonds in PCl₅ whereas in SF₆ both axial bonds and equatorial bonds have the same bond length. Explain.

(i)Discuss the concept of hybridization. What are its different types in a carbon atom?

(ii) What is the type of hybridisation of carbon atoms marked with star.

Comprehension given below is followed by some multiple choice questions. Each question has one correct option. Choose the correct option.

Molecular orbitals are formed by the overlap of atomic orbitals. Two atomic orbitals combine to form two molecular orbitals called bonding molecular orbital (BMO) and anti bonding molecular orbital (ABMO). Energy of anti bonding orbital is raised above the parent atomic orbitals that have combined and the energy of the bonding orbital is lowered than the parent atomic orbitals. Energies of various molecular orbitals for elements hydrogen to nitrogen increase in the order :

σσ < σ *1s < σ2s < (π2p_x = π2p_y) < σ2p₂ < σ2p_z < (π * 2p_x = π*2p_y) < σ* 2p_z s ( p p) p ( * p * p) * p < and for oxygen and fluorine order of energy of molecular orbitals is given below :

σls < σ* 1s < σ2s < σ* 2s < σ2p_z < (π2p_x = π2p_y) < (π* 2p_x = π * 2p_y) < σ* 2p_z

Different atomic orbitals of one atom combine with those atomic orbitals of the second atom which have comparable energies and proper orientation. Further, if the overlapping is head on, the molecular orbital is called ‘Sigma’, (σ) and if the overlap is lateral, the molecular orbital is called ‘pi’, (π). The molecular orbitals are filled with electrons according to the same rules as followed for filling of atomic orbitals. However, the order for filling is not the same for all molecules or their ions. Bond order is one of the most important parameters to compare the strength of bonds.

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

Which of the following molecular orbitals has a maximum number of nodal planes?

(i) σ*1s

(ii) σ*2p_z

(iii) π2p_x

(iv) π*2p_y

Which of the following pair is expected to have the same bond order?

(i) O₂ , N₂

(ii) O⁺₂ , N₂^-

(iii) O₂^- , N⁺₂

(iv) O^-₂ , N^-₂

In which of the following molecules, σ2p_z molecular orbital is filled after π2p_x and π2p_y molecular orbitals?

(i) O₂

(ii) Ne₂

(iii) N₂

(iv) F₂