Can you please explain your full reasoning and use eqilibriu

Can you please explain your full reasoning. and use eqilibrium principles?

3. (5pts) A student made a miraculous discovery and said a hydrate of cobalt (II) chloride changes color as a result of the presence of water vapor, as shown in the reaction below. Is the student correct, does the compound change to pink color indicating moist air? Or is the student wrong because the equilibrium doesn\'t change because water has no effect on the equilibrium? [Co(OH2)6Cl2(s)% [Co(OH2)4]Cl2 + 2 H2O (g) Pink Blue

Solution

Addition of water or presence of moisture will shift the equilibrium.Thus pink colour will appear due to shifting of equilibrium.

BUT very important to be noted:

An equilibrium exists between a hydrated cobalt species and anhydrous cobalt chloride, both have an oxidation state of 2+. See the equilibrium below:

[Co(H₂O)₆]²⁺(aq) + 4 Cl- <–> [CoCl₄]₂-(aq) + 6H₂O
     
    (pink)                                          (blue)

A change in temperature or concentration of the ions will shift the equilibrium. If heat is added, the equilibrium will shift towards the cobalt chloride complex, which is blue in color. Cooling will shift the products towards the hydrated complex, which is more pink. If the chloride or cobalt concentrations increase, the equilibrium will also shift towards the blue anhydrous cobalt chloride. Add water, however, and the equilibrium will shift back towards the pink hydrated species.

So colour change cannot be taken as presence of moisture it may be due to temperature change.