Chemical Equilibrium — A/L Chemistry

What must I remember about Chemical Equilibrium?

• Dynamic equilibrium occurs in closed systems when the rate of the forward reaction equals the rate of the reverse reaction and macroscopic properties remain constant.
• Equilibrium constant expressions: Kc uses molar concentrations (omit pure solids and pure liquids); Kp uses partial pressures for gaseous systems.
• Relationship between Kp and Kc: Kp = Kc(RT)^Δn, where Δn = moles of gaseous products - moles of gaseous reactants.
• Le Chatelier's principle: if a dynamic equilibrium system is subjected to a disturbance in concentration, pressure, or temperature, it shifts to counteract that disturbance.
• Catalysts increase both forward and reverse rates equally by lowering activation energy; they speed up reaching equilibrium without altering Kc or equilibrium composition.

Test yourself (1 minute)

1. What changes the numerical value of Kc and Kp?

   Only temperature changes the numerical value of Kc and Kp; concentration and pressure shifts alter the reaction quotient Q without altering K.

2. Exothermic reactions (ΔH < 0)

   increasing temperature shifts equilibrium backward, decreasing Kc.

3. Endothermic reactions (ΔH > 0)

   increasing temperature shifts equilibrium forward, increasing Kc.

Practise Chemical Equilibrium questions today

Source: NIE G.C.E. (A/L) Chemistry Syllabus (Unit 12)

What should I study first?

Next in the syllabus

Where does Chemical Equilibrium fit in the syllabus?

Grade 13 · Term 1