Nitrogen (II) oxide and chlorine react according to the equation 2NO(g) + Cl2(g) → 2NOCl(g); ΔH = -38 kJ mol⁻¹ The activation energy for the forward reaction is 62 kJ mol⁻¹ - VCE - SSCE Chemistry - Question 20 - 2004 - Paper 1

To find the activation energy of the reverse reaction, we use the relation:

$E_a (reverse) = E_a (forward) + |\Delta H|$

Given:

• The activation energy of the forward reaction, (E_a (forward) = 62 , kJ , mol^{-1})
• The enthalpy change for the reaction, (\Delta H = -38 , kJ , mol^{-1}), thus (|\Delta H| = 38 , kJ , mol^{-1})

Calculating:

$E_a (reverse) = 62 \, kJ \, mol^{-1} + 38 \, kJ \, mol^{-1} = 100 \, kJ \, mol^{-1}$

Therefore, the answer is D. 100.