Question 1

Find the correct statement related to the Lewis structures:&#10;A) Lewis structure does not show the actual structure of the chemical species, it shows only the pattern of bonding and non-bonding electron pairs.&#10;B) The atoms of higher electronegativity is taken as a central atom of polyatomic species because it has to accommodate all electron pairs that are not placed in the bonds.&#10;C) Lewis structure provides a very detailed information on bonding and structure.

Accepted Answer

Lewis structures represent the distribution of electrons in molecules, focusing on electron pairs around atoms and the bonds between atoms, but they do not depict the actual 3D structure or angles between bonds.

Question 2

According to the VSEPR theory, the following can be said for XeF₄ with two lone electron pairs on Xe atom and four Xe-F bonds: A) The molecular geometry is octahedral with lone electron pairs located on the equatorial plane. B) The molecular geometry is square planar with two lone electron pairs on the opposite sides of the molecular plane. C) The molecular geometry is see-saw and two lone electron pairs are at 90$\degree$to each other and all other Xe-F bonds.

Accepted Answer

The VSEPR theory predicts that with four bonding pairs and two lone pairs on the central atom (Xe), the molecular geometry will adjust to minimize repulsion, resulting in a square planar shape. The lone pairs are positioned on opposite sides of the molecular plane to further reduce electron pair repulsion.

Question 3

SF₆ molecule has no lone electron pairs on sulfur. Determine: (i) the number of electrons around sulfur, (ii) the geometry of this molecule and (iii) hybridization scheme on sulfur: A) (i) twelve electrons, (ii) octahedral geometry, (iii) sp³d² B) (i) eight electrons, (ii) octahedral geometry, (iii) sp³d² C) (i) six electrons, (ii) square pyramid, (iii) sp²d²

Accepted Answer

(i) Sulfur in SF₆ has 12 electrons around it (6 from sulfur itself and 6 from the single bonds with fluorine). (ii) With 6 regions of electron density (6 bonding pairs), the geometry is octahedral. (iii) The hybridization scheme for sulfur in this configuration is sp^3d^2.

Question 4

According to the VSEPR model:&#10;A) The shape of the molecule is based on how regions of electron density are arranged in 3D space.&#10;B) The shape of the molecule is based on the arrangement of atoms in 3D space, and not on the arrangement of regions of electron density.&#10;C) The shape of the molecule is based on both the arrangement of atoms in 3D space and the arrangement of regions of electron density.

Accepted Answer

The answer of According to the VSEPR model:&#10;A) The shape...

Question 5

According to the molecular orbital theory:&#10;A) molecular orbitals are products of vawefunctions describing the atomic orbitals; two atomic orbitals produce only one molecular orbital&#10;B) bonding molecular orbitals are lower in energy than the atomic orbitals they were formed from, while antibonding molecular orbitals have greater energy than the original atomic orbitals.&#10;C) Sigma molecular orbitals are always centrosymmetric and cannot have any nodes.

Accepted Answer

Molecular orbital theory posits that when atomic orbitals combine, they form molecular orbitals where electrons are delocalized over the entire molecule. Bonding molecular orbitals result from constructive interference of atomic orbitals, leading to lower energy than the original atomic orbitals. Conversely, antibonding molecular orbitals are formed from destructive interference, resulting in higher energy than the atomic orbitals they originate from.

Question 6

If atom A has an s valence orbital and atom B has one s and three p valence orbitals with p orbitals being close in energy to A's s orbital, how many molecular orbitals can be formed for the AB molecule?

A) A total of five MOs: two bonding, two antibonding and one non-bondiong
B) A total of four MOs: two bonding and two antibonding
C) A total of five: one bonding, one antibonding and three non-bonding.

Accepted Answer

The answer of If atom A has an s valence...

Question 7

Based on the molecular orbital theory, what can we say about the first ionization energy for H₂ molecule? A) It is lower than the first ionization energy of H atom. B) It is higher than the first ionization energy of H atom. C) It is about the same as the first ionization energy of H atom.

Accepted Answer

The molecular orbital theory suggests that when atoms form a molecule, their atomic orbitals combine to form molecular orbitals. In the case of a hydrogen molecule (H2), the bonding molecular orbital is lower in energy than the atomic orbitals of the individual hydrogen atoms. However, the question refers to the first ionization energy, which involves removing an electron from the highest occupied molecular orbital (HOMO). For H2, this would be the bonding molecular orbital. Removing an electron from a molecule generally requires more energy than from an isolated atom because of the additional stability gained through bonding. Therefore, the first ionization energy of H2 (or any molecule formed by hydrogen with another atom, assuming the molecule is more stable than the isolated hydrogen atom) would be higher than that of a hydrogen atom alone.

Question 8

Find the correct statement relating to bond order, bond length and bond strength:&#10;A) Generally, high bond order indicates high bond strength and long bond.&#10;B) Generally, lower bond orders result in longer, weaker bonds.&#10;C) There is no general relationship between bond order and bond strength and length.

Accepted Answer

Generally, lower bond orders result in bonds that are longer and weaker because bond order is indicative of the number of shared electron pairs between two atoms; a higher bond order means more electron pairs are shared, resulting in a stronger, shorter bond.

Question 9

What is a catalytic cycle?&#10;A) It is a cycle of reactions that shows the interconversion of catalyst to products.&#10;B) It is an energy diagram that shows the changes in energy between catalysed and uncatalyzed reaction.&#10;C) It is a sequence of reactions that converts the reactants into products, with the catalyst being regenerated after the cycle.

Accepted Answer

A catalytic cycle is a sequence of chemical reactions that converts reactants into products, with the catalyst being regenerated at the end of the cycle, allowing it to participate in the process again without being consumed.

Question 10

We can say that a catalyst is selective if:&#10;A) it prefers one reactant over another&#10;B) it gives a high yield of a desired product with a small amount of side product(s).&#10;C) it is very selective for one functional group only.

Accepted Answer

A selective catalyst is one that favors the formation of a desired product over other potential products, thus giving a high yield of that product with minimal side products. Choices A and C describe aspects of specificity and selectivity towards reactants or functional groups, but B directly addresses the concept of selectivity in terms of product yield and purity.

Deck 2: Molecular Structure and Bonding