Problem 150 - A Complete Resource Book in Chemistry for JEE Main

Question

The correct statements if the following are: (a) The bond angle of hybrid bonds increases as \(\mathrm{sp}^{3}<\) \(\mathrm{sp}^{2}<\mathrm{sp}\) (b) For hydrogen halides, bond length increases as \(\mathrm{HF}<\mathrm{HCl}<\mathrm{HBr}<\mathrm{HI} .\) (c) Increasing order of bond energy : Single bond \(<\) Double bond \(<\) Triple bond.

Step-by-Step Solution

Answer

All the statements are correct.

Step 1: Identify the Bond Hybridization

Hybridization involves the mixing of atomic orbitals to form new hybrid orbitals suitable for chemical bonding. The hybrid orbitals \(sp^3\), \(sp^2\), and \(sp\) represent different geometries with bond angles of approximately 109.5°, 120°, and 180°, respectively. Therefore, the bond angle generally follows the order \(sp^3 < sp^2 < sp\). This is correct.

Step 2: Analyze Bond Length Trend

The bond length in diatomic molecules like hydrogen halides is determined by the size of the halogen atom bonded to hydrogen. Fluorine, being the smallest, results in a shorter bond, while iodine, being the largest, results in a longer bond. Thus, the bond length increases as \(\text{HF} < \text{HCl} < \text{HBr} < \text{HI}\). This statement is correct.

Step 3: Evaluate Bond Energy Order

Bond energy is indicative of the strength of a chemical bond. In general, triple bonds are stronger than double bonds, which are stronger than single bonds. Therefore, the bond energy increases in the order of single bond < double bond < triple bond. This statement is correct.

Key Concepts

Hybridization

Hybridization is the process of combining atomic orbitals into new hybrid orbitals, suitable for the pairing of electrons to form chemical bonds. The three primary types of hybridization are sp, sp\(^2\), and sp\(^3\).

• sp Hybridization: Offers a linear geometry with bond angles of 180°.
• sp\(^2\) Hybridization: Forms a trigonal planar shape with bond angles around 120°.
• sp\(^3\) Hybridization: Produces a tetrahedral structure with bond angles close to 109.5°.

The bond angle increases as sp\(^3\) < sp\(^2\) < sp. This is due to the different orbital geometries and the electron pair repulsions involved.

Bond Angles

Bond angles are the angles formed between adjacent bonds at an atom. They are crucial in determining molecular shape.

• Tetrahedral Angle: Found in sp\(^3\) hybridization, approximately 109.5°.
• Trigonal Planar Angle: Common in sp\(^2\) hybridization, roughly 120°.
• Linear Angle: Characteristic of sp hybridization, 180°.

These angles are influenced by the presence of lone electron pairs and differences in atomic size and electronegativity.

Bond Energy

Bond energy refers to the amount of energy required to break a bond between two atoms. It serves as an indicator of the bond's strength.

• Single Bonds: Generally have lower bond energy.
• Double Bonds: Stronger than single bonds and contain one sigma and one pi bond.
• Triple Bonds: The strongest, consisting of one sigma bond and two pi bonds.

The order of increasing bond energy is: single < double < triple. This occurs because multiple bonds involve more electron sharing between atoms, increasing the bond strength.

Bond Length Trends

Bond length refers to the distance between the nuclei of two bonded atoms. Factors affecting bond length include atomic size and bond order.

• Atomic Size: Larger atoms form longer bonds. For example, in hydrogen halides, iodine forms the longest bond because it is the largest atom.
• Bond Order: Higher bond orders (more bonds) result in shorter bond lengths.

In hydrogen halides, the bond length order is HF < HCl < HBr < HI, reflecting the size of the halogen atom linked to hydrogen.