TCE Chemistry — Level 4
Chemical Equilibrium — Flashcards & Quiz
Chemical equilibrium is the state where forward and reverse reaction rates are equal and concentrations of reactants and products remain constant. TCE Chemistry Level 4 asks you to write Kc expressions, apply Le Chatelier's principle to predict shifts, and analyse industrial processes like the Haber and Contact processes. The distinction between Kc (temperature-only sensitivity) and position shifts is a common exam trap.
Sample Flashcards
Q1: What is dynamic equilibrium?
Dynamic equilibrium occurs in a closed system when the rate of the forward reaction equals the rate of the reverse reaction. Macroscopic properties remain constant while reactions continue at the molecular level.
Q2: Write the general expression for Kc and explain what a large Kc indicates.
For aA + bB ⇌ cC + dD: Kc = [C]^c[D]^d / [A]^a[B]^b. Large Kc (>>1) means products favoured; small Kc (<<1) means reactants favoured.
Q3: How does temperature affect equilibrium and Kc?
Temperature is the ONLY factor that changes Kc. Exothermic forward: increasing T shifts left, decreases Kc. Endothermic forward: increasing T shifts right, increases Kc.
Q4: How does pressure affect gaseous equilibrium?
Increasing pressure shifts towards fewer moles of gas. Decreasing pressure shifts towards more moles. Equal moles on both sides — no effect.
Q5: How does adding reactant affect equilibrium?
Increases concentration → Q < Kc → shifts right. Product concentrations increase; added reactant partially consumed.
Sample Quiz Questions
Q1: At dynamic equilibrium, all reactions have stopped.
Answer: FALSE
Forward and reverse reactions continue at equal rates.
Q2: Dynamic equilibrium requires a closed system.
Answer: TRUE
A closed system prevents reactants/products from escaping.
Q3: Pure solids are included in the Kc expression.
Answer: FALSE
Pure solids and liquids have constant concentration and are excluded.
Last updated: March 2026 · 6 flashcards · 5 quiz questions