The chapter opening photograph (page 670) showed how the cobalt(II) chloride equilibrium responded to temperature changes.

(a) Look back at that photograph. Is the conversion of the red cation to the blue anion exothermic or endothermic?

(b) If hydrochloric acid is added to the violet mixture of cobalt(II) ions shown below, the blue CoCl₄²⁻ ion is favored. If water is then added to the mixture, a red solution favoring [Co(H₂O)]²⁺ results. Explain these observations in terms of Le Chatelier’s principle.

(c) How do these observations prove the reaction is reversible?

Transcribed Image Text:

TUO Solution after adding more hydrochloric acid Solution of cobalt(II) chloride in dilute hydrochloric acid Solution after adding more water Photos: Cengage Learning/Charles D. Winters