The effect of concentration on chemical equilibrium

Examining the colour of cobalt(II) chloride in water and hydrochloric acid.

02:30

Chemistry

Keywords

balance, chemical equilibrum, concentration, balance shift, cobalt chloride, water, hydrochloric acid, komplex, complex formation, chlorocomplex, chloro complex, aquacomplex, aqua complex, colour change, anhydrous, water of crystallisation, heating, solution, evaporating dish, Bunsen burner, compound, physics, experiment, chemistry

On-screen labels

Cobalt(II) chloride CoCl₂ ∙ 6H₂O, Concentrated hydrochloric acid HCl, Water H₂O, Heat cobalt(II) chloride in an evaporating dish with a Bunsen burner., When heated, the hydrated compound loses its water of crystallisation and turns into blue, anhydrous cobalt(II) chloride., CoCl₂, Pour a spoonful of blue cobalt(II) chloride into water. , When the blue cobalt(II) chloride is dissolved in water, the cobalt(II) ions form aqua complexes, and the solution turns pink., Pour some cobalt(II) chloride into hydrochloric acid., When cobalt(II) chloride is dissolved in concentrated hydrochloric acid, chloro complexes form and the colour of the solution turns blue., Add concentrated hydrochloric acid to the pink solution and water to the blue one. Observe how the colours of the solutions change., Aqua and chloro complexes formed from cobalt(II) ions can transform into each other only in an equilibrium reaction; the change in the concentration of the substances influences the equilibrium., If we add concentrated hydrochloric acid to the pink solution, the equilibrium shifts, favouring the formation of chloro complexes because of the high concentration of chloride, and the solution turns blue. If we add water to the blue solution, aqua complexes form and the solution turns pink.