Equilibrium - created from Mind Map

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When a reaction is at equilibrium the concentrations of reactants and products are constant because the rates of forward and reverse reaction are equal.

Kc – equilibrium constant in terms of concentration. Usually used for reactions in solution, but can be used for all types of reaction involving concentrations. Kp – equilibrium constant in terms of partial gas pressures. Only used for reactions involving gases.

Kc = [C]c[D]d [A]a[B]b

Top line = concentrations of products raised to the powers of the balancing numbers, multiplied together. Bottom line = concentrations of reactants raised to the powers of the balancing numbers, multiplied together.

Kp = PCcPDd PAaPBb

Top line = partial pressures of the products raised to the powers of their balancing numbers, multiplied together. Bottom line = partial pressures of the reactants raised to the powers of their balancing numbers, multiplied together.

If Kc = 1, then the equilibrium has equal amounts of starting materials and products. • If Kc is much less than 1, then the equilibrium is favouring the side of the reactants, with very few products being formed. We can relate this to ΔG. As this reaction is not spontaneous, ΔG is positive • If Kc is much greater than 1, then we have an equilibrium favouring the side of the products, with most of the reactants being converted. This reaction is occurring spontaneously, so ΔG will be negative

If the temperature of a reaction is increased: - • Exothermic reactions shift the equilibrium to the left (endothermic direction). This makes the bottom line of the equilibrium constant larger and the top line smaller, thereby decreasing the equilibrium constant. • Endothermic reactions shift the equilibrium to the right (exothermic direction). This makes the bottom line smaller and the top line larger, thereby increasing the equilibrium constant.

Rates will be made as fast as possible by increasing temperature or pressure or by adding a catalyst. Energy calculations can discover how much energy needs to be put into a system for the reaction to occur. This avoids the use of unwanted energy. Also, if there is an exothermic reaction, the energy will be harnessed in order to reuse it. 57 Equilibrium yield of a product can be increased by changing temperature, concentration or pressure. The equilibrium constant can be used to tell manufacturers which values of pressure or concentration will give high yield.