Engineering Questions with Answers - Multiple Choice Questions

Materials Science MCQ’s – Atomic Bondings in Solids

1 - Question

Which of the following is a secondary bond?
a) Metallic bond
b) Hydrogen bond
c) Covalent bond
d) Ionic bond
View Answer Answer: b
Explanation: Metallic, covalent, and ionic bonds are strong in nature, hence primary; hydrogen bond has comparatively lower bond energies; hence secondary.

2 - Question

VSEPR stands for Valence Shell Electron Pair Repulsion. This theory helps us predict:
a) Bond angles
b) Bond length
c) Electron energy
d) Shell radius
View Answer Answer: a
Explanation: VSEPR theory implies that electrons in valence shell arrange themselves in a manner so as to experience minimum repulsion from other electrons. For e.g., in a CH4 molecule, all the bonds are symmetrically arranged at approximately 109°

3 - Question

In water, the bond angle between the H-O H-O bond is less than 109° Why?
a) The H atoms attract each other
b) Oxygen atom is much larger than Hydrogen atoms
c) Lone pair-bond pair repulsion is greater than bond pair-bond pair repulsion
d) VSEPR theory does not apply for planar molecules like water
View Answer Answer: c
Explanation: Bond angle is 109° for symmetric molecules like methane. However, it is known that repulsion between a lone pair and a bond pair is more than that between two bond pairs. Hence, bond angle is reduced from 109° so as to experience minimum repulsion from lone pairs.

4 - Question

For covalent molecules, van der Waals radius is always greater than a covalent radius.
a) True
b) False
View Answer Answer: a
Explanation: Van der Waals radius is half the internuclear distance between two non-bonded atoms on their closest approach whereas covalent radius is half the bond length of a homo-nuclear molecule. Since the distance between two bonded atoms is less than non-bonded atoms, hence the answer.

5 - Question

If E1 is the bond enthalpy of a sigma-bond and E2 is that of a pi-bond, then:
a) E1 > E2
b) E1 = E2
c) E1 < E2
d) Can’t be predicted
View Answer Answer: a
Explanation: Since the overlap of orbitals in a sigma-bond is along the internuclear axis contrary to sideways overlap in pi-bonds, the bonding is more effective in a sigma-bond. Hence, E1 > E2. Though, the total energy of a double bond is more than a single bond)

6 - Question

Which of the following molecules is non-linear?
a) Hbr
b) CO2
c) C2H2
d) H2S
View Answer Answer: d
Explanation: H2S is non-linear due to presence of lone pairs on S atom. Hbr being a binary molecule is linear. Double bonds in CO2 and C2H2 also leads to linear geometry.

7 - Question

With an increase in bond length, bond energy:
a) increases
b) decreases
c) may either increase or decrease
d) does not change
View Answer Answer: b
Explanation: The coulombic force of attraction is inversely proportional to the square of a distance between the charges. As the internuclear distance in a bond increases, the force of attraction between nuclei and electrons decreases.

8 - Question

sp3 hybridization is present in which of the following molecules?
a) BeCl2
b) H2O
c) C2H4
d) BCl3
View Answer Answer: b
Explanation: Hybridization takes place between one 2s and three 2p orbitals of Oxygen so as to minimize electronic repulsion. BeCl2, C2H4, and BCl3 have sp, sp2, and sp2 hybridization respectively.

9 - Question

Which of the following is the correct order for bonding energies of molecular orbitals?
a) σ1s < σ2s < σ*2s < σ*1s
b) σ1s < σ2s < σ*1s < σ*2s
c) σ1s < σ*1s < σ2s < σ*2s
d) none of the mentioned
View Answer Answer: c
Explanation: Energy of bonding MO is less than that of anti-bonding MO formed from same atomic orbitals. Also, MO formed from atomic orbitals of higher energy possess higher energy.

10 - Question

Which of the following molecules is diamagnetic?
a) O2
b) CO
c) N+2
d) NO
View Answer Answer: b
Explanation: Out of the above species, only CO does not have unpaired electrons. Others have partially filled molecular orbitals and hence are attracted by external magnetic fields.

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