Problem 6 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The bond energy (in kcal \(\mathbf{m o l}^{-1}\) ) of a \(\mathrm{C}-\mathrm{C}\) single bond is approximately [2010] (a) 1 (b) 10 (c) 100 (d) 1000

Step-by-Step Solution

Answer

The bond energy of a C-C single bond is approximately 100 kcal/mol.

Step 1: Understanding Bond Energy

Bond energy is the measure of the strength of a chemical bond. It is defined as the amount of energy needed to break one mole of a particular type of bond in a gaseous substance. The units of bond energy are typically given in kilocalories per mole (kcal/mol) or kilojoules per mole (kJ/mol).

Step 2: Identify Given Options

The given options are: (a) 1 kcal/mol, (b) 10 kcal/mol, (c) 100 kcal/mol, and (d) 1000 kcal/mol. We need to determine which of these options is approximately the bond energy for a C-C single bond.

Step 3: Recalling Typical Bond Energy for C-C Bond

The typical bond energy for a carbon-carbon single bond is about 83 to 85 kcal/mol. This value is based on empirical data obtained through experiments and documented chemistry references.

Step 4: Selecting the Closest Answer

The closest option to the typical bond energy value of a carbon-carbon single bond (83-85 kcal/mol) given in the choices is option (c) 100 kcal/mol. This makes option (c) the most reasonable selection.

Key Concepts

Chemical Bond

A chemical bond is a force that holds atoms together in a molecule, allowing the formation of chemical compounds. These bonds are crucial in determining the physical and chemical properties of substances. There are different types of chemical bonds, including:

• Covalent Bonds: Where atoms share electrons.
• Ionic Bonds: Where atoms transfer electrons from one to another.
• Metallic Bonds: Where electrons are shared over many nuclei, allowing metals to conduct electricity.

Each bond type has its unique characteristics and energy requirements for forming or breaking. When atoms form a bond, energy is released; conversely, breaking a bond requires energy input. This energy involved in forming or breaking bonds is termed bond energy.

Carbon-Carbon Single Bond

A carbon-carbon (C-C) single bond is one of the simplest forms of covalent chemical bonds. It involves the sharing of one pair of electrons between two carbon atoms. These bonds form the backbone of organic compounds, which include fossil fuels, plastics, and many other man-made and natural substances.

The strength and length of the C-C bond directly affect the stability and reactivity of the compound. Typically, the bond energy needed to break a C-C single bond is around 83-85 kcal/mol, which indicates a relatively high level of stability and strength among single bonds. Understanding C-C bonds is fundamental to studying organic chemistry and materials science.

Energy Measurement

Energy measurement in chemistry involves quantifying the amount of energy required for chemical reactions, particularly in breaking or forming chemical bonds.

Bond energy, often measured in kilocalories per mole (kcal/mol) or kilojoules per mole (kJ/mol), represents the average energy needed to break one mole of a specific bond type in the gaseous state. This measurement helps predict the reactivity and stability of molecules under different conditions.

• Kilocalories (kcal): Commonly used in the context of food energy, but also applicable in chemistry, especially in the U.S.
• Kilojoules (kJ): More widely used in scientific contexts globally, aligning with the International System of Units (SI).

For practical purposes in chemical laboratories and industries, accurate measurement of bond energies allows chemists to design and control reactions efficiently.