- The complex ion [CuCl₄]²⁻ is formed when concentrated hydrochloric acid is added to an aqueous solution of hydrated copper(II) ions.
Cu²⁺ (aq) + 4Cl⁻ (aq) ⇌ [CuCl₄]²⁻ (aq)
(Blue) (Yellow)
(a) State an expression for the equilibrium constant, K꜀, corresponding to this equation. [1]
(b) The numerical value of K꜀ under standard conditions is 4.2 × 10⁵. Calculate the ratio when the chloride ion concentration is 0.210 mol dm⁻³. [2]
(c) Explain why Cu²⁺(aq) is coloured, with reference to its electronic structure and section 17 of the data booklet. [3]
(d) State, with a reason, the effect of an increase in temperature on the value of K꜀. ΔH° > 0 [1]
(e) State, with a reason, the effect of adding aqueous silver nitrate, AgNO₃(aq), on the position of this equilibrium.
Ag⁺(aq) + Cl⁻(aq) ⇌ AgCl(s) [1]