Sindh Mdcat Exclusive Course Chemistry Chemical Bonding — Solved MCQs

Question 1

Which of the following substances exhibits hydrogen bonding?

Accepted Answer

C. NH3 — Hydrogen bonding occurs in those substances in which a highly electronegative atom (such as Fluorine (F), Oxygen (O) or Nitrogen (N)) is directly bonded to Hydrogen. The presence of one of these three atoms is a REQUIREMENT for hydrogen bonding to occur. Only option C mentions a substance which has one of these three atoms, i.e. Nitrogen in NH3, while the other options mention other atoms aside from the three highly electronegative species mentioned previously.

Question 2

The shape of CO2 molecule is similar to:

Accepted Answer

D. BeF2 — CO2 has a linear structure with a bond angle of 180 degrees with the central atom (C) having no lone pairs and being sp hybrid. Beryllium in BeF2 has the same configuration. Other options are wrong because: H2S= sp3 SO2=sp2 SnCl2=sp2

Question 3

Both ionic and covalent bonds are present in:

Accepted Answer

D. NaOH — Sodium hydroxide (NaOH) contains both covalent and ionic bonds. The sodium ion (Na+) and hydroxide ion (OH-) are held together by an ionic bond, while the covalent bond is between the hydrogen and oxygen atoms in the hydroxide ion(-OH).

Question 4

The valency of an atom will be one if there is a sufficient gap between first and second _.

Accepted Answer

B. Ionization energy — The valency of an atom will be one if there is a sufficient gap between the first and second ionization energies. Ionization energy is the energy required to remove an electron from an atom in its gaseous state. The first ionization energy is the energy required to remove the first electron from the atom, and the second ionization energy is the energy required to remove the second electron from the atom.If there is a large gap between the first and second ionization energies, it means that it is much more difficult to remove the second electron than the first electron. This is because the first electron is loosely bound to the atom, but the second electron is more tightly bound.An atom with a large gap between the first and second ionization energies will tend to have a valency of one. This is because the atom will be more likely to lose one electron than two electrons.So the answer is ionization energy.

Question 5

The decreasing order of second ionization energy of K, Ca, Ba is:

Accepted Answer

A. K > Ca > Ba — As we move down the group size increases and the electrons experience less effective nuclear charge. Due to this reason, ionization potential decreases down the group. Thus, the second ionization potential of Ca is greater than that of Ba. The second ionization potential of K is greater than that of Ca as K acquires stable noble gas configuration after losing one electron.

Question 6

The bond, which is based on attractive forces between oppositely charged ions, is:

Accepted Answer

C. Ionic bond — An Ionic bond, also called an electrovalent bond, type of linkage formed from the electrostatic attraction between oppositely charged ions in a chemical compound. Such a bond forms when the valence (outermost) electrons of one atom are transferred permanently to another atom.

Question 7

Which of the following indicate the correct variation of electronegativity?

Accepted Answer

D. F > O > N > C — The relative tendency of a bonded atom in a molecule to attract the shared electron pair towards itself is called electronegativity. The positively charged protons in the nucleus attract the negatively charged electrons. As the number of protons in the nucleus increases, the electronegativity or attraction will increase. Therefore electronegativity increases from left to right in a row in the periodic table. Here, the correct order of electronegativity is: F > O > N > C

Question 8

Linear combination of atomic orbitals (LCAO) results in the formation of:

Accepted Answer

D. Bonding and antibonding molecular orbitals — According to Molecular Orbital Theory (MOT), two atomic orbitals overlap resulting in the formation of molecular orbitals. Number of atomic orbitals overlapping together is equal to the molecular orbital formed. The two atomic orbital thus formed by LCAO (linear combination of atomic orbital) in the same phase or in the different phase are known as Bonding Molecular Orbital (BMO) and Antibonding Molecular Orbitals (ABMO) respectively.

Question 9

An ionic compound is most likely to be formed when:

Accepted Answer

B. The ionization energy of A is low but electron affinity of B is high — The option "The ionization energy of A is low but electron affinity of B is high" is most likely to form an ionic compound. In an ionic compound, one element has a low ionization energy, which means it readily gives up electrons to form a cation, while the other element has a high electron affinity, which means it readily accepts electrons to form an anion. This results in the formation of an ionic bond between the cation and anion, forming an ionic compound.

Question 10

The raindrop acquires a spherical shape and ink spread over blotting paper due to:

Accepted Answer

A. Surface tension — A raindrop falling through the atmosphere forms a roughly spherical structure due to the surface tension of water. This surface tension is the “skin” of a body of water that makes the molecules stick together. The cause is the weak hydrogen bonds that occur between water molecules.

Question 11

Which of the following molecules have zero Dipole Moment?

Accepted Answer

E. All of the above — All the molecules listed have a zero dipole moment due to their symmetrical structures:CCl4: Although it has polar C-Cl bonds, the tetrahedral symmetry results in a net dipole moment of zero.CO2: The linear shape with two opposing C=O bonds results in the cancellation of dipole moments.Cl2: As it consists of identical atoms, no dipole moment arises.C6H6 (Benzene): The planar symmetrical structure leads to the cancellation of dipole moments of C-H bonds.Therefore, the correct answer is 'All of the above'.

Question 12

Bond energy:I. is the energy required to break a bond between two atoms in a diatomic molecule II. Is taken as the energy released in forming a bond form free atoms III. Is the measure of the strength of bond.

Accepted Answer

E. I, II and III — Bond energy is a critical concept in understanding chemical bonding and is defined through multiple perspectives:Option I: It is indeed the energy required to break a bond between two atoms in a diatomic molecule, indicating how much energy is needed to overcome the bond's strength.Option II: The energy released when a bond is formed from free atoms is also a measure of bond energy, showing the stabilization energy provided during bond formation.Option III: Bond energy serves as an indicator of bond strength; stronger bonds require more energy to break, thus having higher bond energies.Therefore, all three options collectively provide a comprehensive understanding of bond energy, making Option E the correct choice. Each statement highlights a different but related aspect of bond energy, and understanding this concept requires integrating all perspectives.

Question 13

GN Lewis described which one of the following bonds?

Accepted Answer

D. All of the above — G.N. Lewis is renowned for his work on the nature of chemical bonding, particularly the sharing of electron pairs between atoms, which forms the basis of covalent bonds. His theories extend to both ordinary covalent bonds and coordinate covalent bonds. While ionic bonds involve electron transfer and are not the primary focus of Lewis's theories, his work laid the groundwork for understanding chemical bonding as a whole. Therefore, 'All of the above' is the correct answer, as it encompasses the types of bonds Lewis described.

Question 14

The order of force of repulsion between Lone pairs and Bond pairs is?

Accepted Answer

D. Lone pair - Lone pair repulsion > Lone pair - Bond pair repulsion > Bond pair - Bond pair repulsion — The correct order of repulsions is: Lone pair - Lone pair repulsion > Lone pair - Bond pair repulsion > Bond pair - Bond pair repulsion. This is because lone pairs of electrons are not shared between atoms and are therefore more concentrated and closer to the central atom, leading to greater repulsion. Lone pair - bond pair repulsion is less than lone pair - lone pair but more than bond pair - bond pair, as the presence of a lone pair introduces more electron density compared to the shared electron density in bond pairs. Bond pair - bond pair repulsion is the weakest due to the attraction between the electrons and their respective nuclei, which stabilizes the electrons in the bond.

Question 15

Ionic, covalent and co-ordinate covalent bonds are simultaneously present in the molecular geometry of:

Accepted Answer

B. Ammonium hydroxide — There are 3 covalent , 1 coordinate covalent bond in NH4+ ion, and 1 covalent bond in OH−. There is an ionic bond between NH4+ and OH-.So, this species simultaneously has 3 different types of bonds.

Question 16

In HF the covalent bond is due to:

Accepted Answer

B. S-Pz overlapping — In formation of HF, 1s orbital of H overlaps with 2Pz orbital to F to form bond. Therefore bonding is due to S-Pz overlapping.

Question 17

Which statement is incorrect regarding a chemical bond?

Accepted Answer

D. Bond formed by the large sized atoms is strong — Bonding tends to take place between the outermost electrons of an atom (or outermost shell). As you increase the atomic size, the electrons that make up an atom begin to fill up higher electron orbitals. These orbitals, which then take place in bonding, are physically further away from the nucleus and thus experience less attraction to it (based on Columb's law). That is the reason why D is an incorrect statement and thus the answer. A is true as the overlapping of half-filled orbitals occurs in covalent bonding; a type of chemical bond. B is true as it occurs in the formation of ionic bonds. C is also true as the s orbital is the smallest orbital because of which the distance between outermost electrons and the positively charged nucleus is small, rendering a stronger attractive force.

Question 18

For the formation of ionic bond, electronegativity difference should be:

Accepted Answer

C. More than 1.7 — Electronegativity is a measure of an atom's ability to attract electrons towards itself in a chemical bond. For the formation of an ionic bond, there should be a significant difference in electronegativity between the participating atoms. Typically, an electronegativity difference of 1.7 or greater on the Pauling scale is considered indicative of an ionic bond. In other words, if the electronegativity difference between two atoms is equal to or greater than 1.7, it suggests that one atom has a much stronger attraction for electrons than the other.

Question 19

Which one of the following bonds has the highest bond energy?

Accepted Answer

C. N ≡ N — Triple bonds are stronger than single and double bonds, for understandable reasons. A nitrogen-nitrogen triple bond is stronger than a carbon-carbon triple bond because as we know that in the periodic table as we move from left to right the atomic sizes of elements decrease, this is due to the addition of electrons in the valence shell which increases nuclear charge. Carbon and nitrogen both elements are present in the same period but nitrogen (Z=7) is placed next to carbon (Z=6) thus it means the size of nitrogen is smaller than that of carbon and thus both the nitrogen atoms are much closer to each other unlike in case of carbon and hence more energy is required to break N-N triple bond compared to C-C triple bond.

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