CHEMISTRY · Single correct · A Level · Chemistry · Kinetics · Kinetics
Problem
Three elementary gas-phase reactions are proposed. Average bond energies (kJ mol⁻¹) are: N≡N 945, O=O 498, Cl–Cl 243, N–O 201, O–H 463, H–Cl 431.
Reaction 1: N2+2O→2NO (breaks one N≡N; forms two N–O)
Reaction 2: O2+2H→2OH (breaks one O=O; forms two O–H)
Reaction 3: Cl2+2H→2HCl (breaks one Cl–Cl; forms two H–Cl)
Assuming the primary factor controlling the activation energy is the strength of bonds that must be broken in the reactants, which reaction is expected to have the largest activation energy?
(a) Reaction 2
(b) Reaction 3
(c) Reaction 1
(d) All three should have similar activation energies because the same number of bonds are broken