Chemical Bonding And Molecular Structure

To solve the problem, we need to determine the bond enthalpy of given the ratio of bond enthalpies and the bond enthalpy of formation of . Let us proceed step by step.

Step 1: Define the variables
Let:
- The bond enthalpy of be .
- The bond enthalpy of be .
- The bond enthalpy of be .

From the problem, we are given:
1. The ratio of bond enthalpies is .
2. The bond enthalpy of formation of is .

Step 2: Express the bond enthalpies in terms of a common variable
Using the ratio , we can write:
$ k AB AB x y z k AB -100 \, \text{kJ mol}^{-1} k -2 B_2 B_2 y = k k = 200 $

Let's evaluate each statement:

• Hydrogen bonding is stronger than dispersion forces: This is correct. Hydrogen bonds are stronger than dispersion forces, as hydrogen bonds involve strong electrostatic interactions between a hydrogen atom and highly electronegative atoms like oxygen, nitrogen, or fluorine.
• Sigma bonds are stronger than pi-bonds: This is correct. Sigma bonds, formed by head-on overlap of atomic orbitals, are stronger than pi-bonds, which are formed by side-by-side overlap.
• Ionic bonding is non-directional: This is correct. Ionic bonds are formed between oppositely charged ions, and the force of attraction is the same in all directions around the ion, making it non-directional.
• σ-electrons are referred to as mobile electrons: This is incorrect. π-electrons are referred to as mobile electrons in metals, not σ-electrons. π-electrons are free to move within the electron cloud, contributing to conductivity. σ-electrons are localized and involved in bonding.

Therefore, the incorrect statement is (D): σ-electrons are referred to as mobile electrons

Correct Answer:

Explanation:
To determine the bonding in diatomic molecules like and , we use Molecular Orbital Theory (MOT).

• O₂ molecule:
- Total bond order: 2 (based on MO diagram)
- Bonding: 1 σ bond (from or ) and 1 π bond (from & )
⇒ So, bonding in : 1σ and 1π

• C₂ molecule:
- Total bond order: 2
- Due to the electron configuration, the two bonds in C₂ are both π bonds.
- There is no net σ bond from 2p orbitals.
⇒ So, bonding in : 0σ and 2π

Therefore, the correct bonding is:

Bond Length: The distance between the nuclei of two bonded atoms.

Bond Order: A measure of the number of chemical bonds between a pair of atoms; the formula is .

The incorrect statement is:

1. Bond length of < Bond length of
2. Bond order of > Bond order of
3. Bond length of > Bond length of
4. Bond order of < Bond order of

The correct answer is that statement 2 is incorrect because the bond order of is equal to the bond order of , not less than it.