Understanding Dynamic Equilibrium
Equilibrium is a state where forward and reverse reactions occur at the same rate. In a closed system, this means the concentrations of reactants and products remain constant, even though the reactions never truly stop.
Changing Equilibrium Conditions
According to Le Chatelier’s Principle, if a dynamic equilibrium is subjected to a change in conditions, the position of equilibrium shifts to counteract that change.
Standard baseline temperature. Neither thermal direction is artificially favored.
Standard baseline pressure. No pressure-driven mole disparity advantage.
An increase in temperature always favours the endothermic direction (+ΔH). A decrease in temperature favours the exothermic direction (-ΔH).
An increase in pressure shifts equilibrium to the side with fewer moles of gas. A decrease shifts to more moles. If gaseous moles are equal, pressure changes do not shift equilibrium.
A catalyst speeds up both forward and reverse rates equally. It helps equilibrium be reached faster but never alters the position of equilibrium or the yield.
Current Equilibrium Note: Ammonia Synthesis (Haber Process)
4 moles of gaseous reactants form 2 moles of gaseous product. Forward reaction releases thermal energy.
A catalyst is a substance that increases the rate of a chemical reaction by providing an alternative reaction pathway with a lower activation energy, and remains chemically unchanged at the end of the process.
Because the activation energy is lowered by identical amounts in both forward and reverse directions, the forward and reverse reaction rates increase equally. Therefore, a catalyst does not alter the position of equilibrium or the equilibrium yield under fixed conditions.
Alternative Pathway
-42% Ea BarrierProvides a reaction mechanism with a lower activation energy (Ea) threshold.
Equal Rate Acceleration
Equal Rate (kf & kr)Speeds up both the forward and reverse reactions by the exact same proportion.
Zero Yield Shift
ΔYield = 0%Does not shift equilibrium position or increase product yield; equilibrium is reached faster.