JEE Challenger
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ChemEasyAdv 2010 • Paper 1

Approximate Bond Energy of Carbon Carbon Single Bond

The bond energy (in kcal mol−1\mathbf{kcal\ mol^{-1}}) of a C--C single bond is approximately

Options

A

1

B

10

C

100

Correct
D

1000

Topics & Concepts

ThermodynamicsEnthalpy

Step-by-Step Solution

To determine the approximate bond dissociation energy of a Carbon-Carbon (C-C\text{C-C}) single bond:

  1. Experimental Value in SI Units:
    The typical bond enthalpy of a covalent C-C\text{C-C} single bond is approximately 347 kJ mol−1347 \text{ kJ mol}^{-1} to 350 kJ mol−1350 \text{ kJ mol}^{-1}.

  2. Conversion to kcal mol−1\text{kcal mol}^{-1}:
    Using the conversion factor between Joules and Calories (1 kcal=4.184 kJ1 \text{ kcal} = 4.184 \text{ kJ}):
    Bond Energy≈347 kJ mol−14.184 kJ kcal−1≈82.9 kcal mol−1\text{Bond Energy} \approx \frac{347 \text{ kJ mol}^{-1}}{4.184 \text{ kJ kcal}^{-1}} \approx 82.9 \text{ kcal mol}^{-1}

  3. Order of Magnitude Approximation:
    Comparing 83 kcal mol−183 \text{ kcal mol}^{-1} to the given choices:

    • 1 kcal mol−11 \text{ kcal mol}^{-1}
    • 10 kcal mol−110 \text{ kcal mol}^{-1}
    • 100 kcal mol−1100 \text{ kcal mol}^{-1}
    • 1000 kcal mol−11000 \text{ kcal mol}^{-1}

The value 83 kcal mol−183 \text{ kcal mol}^{-1} is closest to 100 kcal mol−1100 \text{ kcal mol}^{-1}.

Thus, the approximate bond energy of a C-C\text{C-C} single bond is 100 kcal mol−1100 \text{ kcal mol}^{-1}.

Correct Answer: C

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