Problem 32 - A Complete Resource Book in Chemistry for JEE Main

Question

The molecule having highest bond energy is (a) \(\mathrm{N}-\mathrm{N}\) (b) \(\mathrm{F}-\mathrm{F}\) (c) \(\mathrm{C}-\mathrm{C}\) (d) \(\mathrm{O}-\mathrm{O}\)

Step-by-Step Solution

Answer

The molecule with the highest bond energy is \\ \( \mathrm{C}-\mathrm{C} \\).

Step 1: Understanding Bond Energy

Bond energy is the measure of bond strength in a chemical bond. The higher the bond energy, the stronger the bond. It's measured in kilojoules per mole (kJ/mol).

Step 2: Identifying Common Bond Energies

Typical bond energies are: 1. \ \( \mathrm{N}-\mathrm{N} \: 163 \, \mathrm{kJ/mol} \ \)2. \ \( \mathrm{F}-\mathrm{F} \: 158 \, \mathrm{kJ/mol} \ \)3. \ \( \mathrm{C}-\mathrm{C} \: 348 \, \mathrm{kJ/mol} \ \)4. \ \( \mathrm{O}-\mathrm{O} \: 146 \, \mathrm{kJ/mol} \ \)

Step 3: Comparing the Bond Energies

Among the bond energies listed, the \ \( \mathrm{C}-\mathrm{C} \) bond has the highest energy of 348 \, \mathrm{kJ/mol}, indicating it is the strongest bond among the given options.

Key Concepts

Understanding Chemical Bonds

A chemical bond is a lasting attraction between atoms that enables the formation of chemical compounds. These bonds are the "glue" that hold atoms together, allowing them to form molecules and compounds. Chemical bonds result from the interaction of valence electrons in atoms and the desire of atoms to reach a more stable state.
Covalent bonds, ionic bonds, and metallic bonds are three primary types of chemical bonds.

• Covalent Bonds: These occur when two atoms share one or more pairs of electrons. This sharing enables each atom to achieve a full outer electron shell, which is often associated with stability. An example is the strong \( \mathrm{C}-\mathrm{C} \) bond observed in organic compounds.
• Ionic Bonds: These result from the transfer of electrons from one atom to another, leading to the formation of oppositely charged ions that attract each other.
• Metallic Bonds: These involve a "sea of electrons" that are free to move around, which accounts for the conductivity and malleability of metals.

Chemical bonds are fundamental in chemistry as they determine the structure and properties of molecules. Studying these bonds helps us understand how molecules interact, react, and form new compounds.

Exploring Bond Strength

Bond strength is an essential concept that reflects how tightly two atoms are held together in a chemical bond. It is determined by the amount of energy required to break a bond and is linked closely with bond energy. The bond strength affects various physical properties of the materials, such as boiling and melting points, and can influence chemical reactivity.

• Single, Double, and Triple Bonds: The bond strength also varies with whether the bond is single, double, or triple, with triple bonds being the strongest and single bonds the weakest. For example, the triple bond in nitrogen gas (\( \mathrm{N} \equiv \mathrm{N} \) ) is exceedingly strong.
• Factors Influencing Bond Strength: Electron affinity, atomic size, and electronegativity differences contribute to how strong a bond can be. Generally, smaller atoms with higher electronegativity form stronger bonds.

Understanding bond strength is crucial for predicting molecular stability and how molecules might interact during chemical reactions. This knowledge can be applied in areas ranging from material science to pharmaceutical developments.

Measuring in Kilojoules per Mole

Energy in chemistry is often measured in kilojoules per mole (kJ/mol), which provides a standard unit to gauge the energy involved in the formation or breaking of chemical bonds. This measurement is crucial for chemists to communicate how much energy processes like reactions and bond formations require or release.

• Bond Energy: The bond energy indicates how much energy is needed to break one mole of a bond in a molecule, and it's a direct reflection of bond strength. For example, the \( \mathrm{C}-\mathrm{C} \) bond in the provided example has a bond energy of 348 \, \mathrm{kJ/mol}, making it stronger than the others.
• Exothermic and Endothermic Processes: These terms describe whether a reaction releases (exothermic) or absorbs (endothermic) energy. When bonds form, energy is released, hence making this an exothermic process. Conversely, breaking bonds requires energy, resulting in an endothermic process.

Understanding these energy measurements allows scientists to predict the feasibility and spontaneity of chemical reactions, as well as to design new reactions and synthesize compounds efficiently.