When cobalt(II) chloride is added to pure water, the Co2+ ions are either hydrated to give a pink color, or combined with chlori
de ion to give a blue color, reaching an equilibrium shown here: Co(H2O)62+ + 4Cl- ↔ CoCl42- + 6H2O
If the forward reaction is exothermic, which statement below describes the change that the system will undergo if the temperature of the solution decreases.
(A) solution will change color
(B) not enough info is given
(C) solution will turn more pink
(D) solution will turn more blue
An exothermic reaction increases the temperature of the system and an endothermic reaction decreases the temperature.
In an equilibrium, if the forward reaction is exothermic, the reverse reaction is endothermic. Therefore, the decrease of temperature inicates that the reverse reaction is favored.
The reverse reaction in the example produces the hydrated Co²⁺, which gives a pink color to the solution. Therefore, solution will turn more pink.
