The equilibrium constant KcEdexcel A-Level Chemistry: Mind map

Exam questions on The equilibrium constant Kc

1. Iron(III) ions react with thiocyanate ions in aqueous solution to form a blood-red complex ion: Fe³⁺(aq) + SCN⁻(aq) ⇌ [Fe(SCN)]²⁺(aq). A student studies the equilibrium mixture.
   The equation is rewritten as 2Fe³⁺(aq) + 2SCN⁻(aq) ⇌ 2[Fe(SCN)]²⁺(aq). Deduce the expression for Kc for this equation and state how it is related to Kc for the original equation.2 marks
2. Calcium carbonate decomposes when heated strongly in a sealed container: CaCO₃(s) ⇌ CaO(s) + CO₂(g). A student investigates this heterogeneous equilibrium.
   Deduce the expression for Kc for the equilibrium 3Fe(s) + 4H₂O(g) ⇌ Fe₃O₄(s) + 4H₂(g).2 marks
3. Methanol is manufactured from carbon monoxide and hydrogen: CO(g) + 2H₂(g) ⇌ CH₃OH(g). All three substances are gases.
   Deduce the expression for Kc for the formation of methanol. Deduce the expression for Kc' for the decomposition of methanol, CH₃OH(g) ⇌ CO(g) + 2H₂(g), and state how Kc' is related to Kc.3 marks