MDCAT Chemistry MCQ #1752

The bond energy of H-H is 436 kJ/mol and Cl-Cl is 242 kJ/mol. If the enthalpy of formation of HCl is -92 kJ/mol, calculate the H-Cl bond energy.

MDCAT Chemistry MCQ #1752

  1. Question 1

    Q1. The bond energy of H-H is 436 kJ/mol and Cl-Cl is 242 kJ/mol. If the enthalpy of formation of HCl is -92 kJ/mol, calculate the H-Cl bond energy.

    • A) 339
    • B) 431
    • C) 678
    • D) 184

    Answer: 431

    Explanation: Using Hess's law, BE(H-Cl) = 0.5*BE(H-H) + 0.5*BE(Cl-Cl) - dHf. 431 kJ/mol is the result. 339 fails by ignoring the enthalpy of formation.