The following equation represents a gaseous reaction that takes place in a sealed container - VCE - SSCE Chemistry - Question 3 - 2022 - Paper 1

The units for the equilibrium constant expression $K_c$ are derived from the ratio of concentrations.

• For the given expression:

$[K_c] = \frac{(mol/L)^2(mol/L)^6}{(mol/L)^4(mol/L)^3} = \frac{(mol/L)^8}{(mol/L)^7} = mol/L$ Thus, the units for $K_c$ are mol/L.

According to Le Chatelier's Principle, increasing the temperature of an exothermic reaction (where (ΔH < 0)) will shift the equilibrium position to favor the endothermic direction, which in this case is the formation of reactants (NH₃ and O₂). This implies that the equilibrium constant, $K_c$, will decrease as temperature increases, as the position of equilibrium favors the reactants more.

At the original equilibrium, the rate of the forward reaction is determined by the concentration of reactants, NH₃ and O₂. When the temperature increases, the average energy of the molecules increases, leading to more frequent and effective collisions. Due to this increased kinetic energy and collision frequency, the rate of the forward reaction at the new equilibrium will be higher compared to the original equilibrium. Collision theory suggests that not only does the number of collisions increase, but more molecules will possess enough energy to overcome the activation energy barrier, thus increasing the reaction rate.