Asked in Premeth Test 11 — S and P Block, D Block and Chemical Bonding (13 March 2025) 2025Moderate

Predict the highest bond energy of the following single bond:

Correct answer: A. C - H

  • A. C - H
  • B. C - N
  • C. C - O
  • D. C - C

Explanation

Smaller the atom bonded lesser will be the bond length and higher will be the bond energy The highest bond energy among the given single bonds is C - H.Here's why:Bond energy is the measure of the strength of a chemical bond. It's the energy required to break one mole of bonds in gaseous molecules. Factors affecting bond energy:Bond length: Shorter bonds are generally stronger and have higher bond energies. Electronegativity difference: Greater electronegativity difference between the bonded atoms generally leads to a stronger, more polar bond, and thus higher bond energy.Considering these factors:C-H: This bond is relatively short and has a significant electronegativity difference between carbon (2.55) and hydrogen (2.20).C-N: This bond is slightly longer than C-H and has a larger electronegativity difference between carbon (2.55) and nitrogen (3.04).C-O: This bond is also slightly longer than C-H and has an even larger electronegativity difference between carbon (2.55) and oxygen (3.44).C-C: This bond is longer than C-H and has no electronegativity difference (both atoms are carbon).While the electronegativity difference is largest for C-O, the C-H bond is shorter, and this shorter bond length has a greater influence on bond energy. Therefore, C-H bonds are generally stronger than C-O bonds.Typical bond energies (approximate values in kJ/mol):C-H: 413C-C: 348C-N: 305C-O: 358As you can see, the C-H bond has the highest bond energy among those listed.

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About Bond Energy

Bond energy is the energy needed to break one mole of a particular covalent bond in gaseous molecules, while bond formation releases energy. Reaction enthalpy is estimated by subtracting the total energy of bonds formed from bonds broken, with attention to average bond energies and their limitations for specific molecules.

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