In The Equilibrium Law we learned that K_c for an equilibrium system is a constant at constant temperature. In this topic we're going to explore what happens if we change the temperature of the equilibrium mixture.

When concentrated hydrochloric acid is added to a solution of cobalt(II) chloride an equilbrium mixture is formed that contains [Co(H₂O)₆]²⁺(aq) and [CoCl₄]^2–(aq) ions.  

This is a good equilibrium to explore because [Co(H₂O)₆]²⁺(aq) ions are a pink colour and [CoCl₄]^2–(aq) ions are a blue colour. We will start with a mixture that contains both ions and is therefore violet.

[Co(H₂O)₆]²⁺(aq) + 4Cl^–(aq) _∏  [CoCl₄]^2–(aq) + 6H₂O(l)

                                                pink                                       blue

We will place the test tube containing the equilibrium mixture into a beaker of hot water and into a beaker containing ice and water.

[INSERT CI_01_vid]

Work through the following drag and drop activity to check your understanding of the effect of temperature on the position of equilibrium and on K_c.

[INSERT CI_08_int]