CH 22 Le Chateliers Principle in a Cobalt Complex Worksheet

Le Chatelier’s Principle in a Cobalt Complex Worksheet

Name: Hope Robertson TA: Sam Mumford

Table: Observations of manipulation of the cobalt complex
Color
Dark blue, very rich viscous solution
2-
[CoCl ]
4 (aq)


Pink lemonade color;
] 2+
[Co(H2O)6(aq) translucent light pink/orange color

Step 3 Color change and Pink color to light blue to dark blue.
observations
(addition of HCl)
Step 5 Color change and causes the dark blue to become more clear and translucent
observations
(addition of H₂O)
Step 6 Color change and solution with H₂O, turned very dark blue
observations solution of just HCl and CoCl₄,
(Heating) very dark blue
Step 7 Color change and solution with H₂O, light blue → to clear/transparent → Light purpl
observations color
(Cooling) solution of just HCl and CoCl₄,
very dark blue → lighter blue but not very big change
Step 8 Color Change and dark blue turns to light purple/pink and becomes more translucen
observations white/pink precipitate forms
(Addition of AgNO₃ 0.1M)


Questions:
1. What was the effect of adding excess chloride ions. Use Le Chatlier’s principle and
provide evidence.
2+
The addition of excess chloride ions saturates the [ Co(H2 O)6 ] ”pushing” the equilibrium of the
reaction to the left (see equation 1) creating the blue color (that is the CoCl4).


2. Based upon the heating and cooling of the two equilibrium mixtures, propose if the
reaction is endothermic or exothermic. Use Le Chatlier’s principle and provide evidence
(would heat be considered as a reactant or product?).
2− 2+
1)[ CoCl 4 ]
+ 6H O2 ↔Co(H
[ O)
2 ]6 4 −
+Cl

When heat was added the complex turned a deep shade of blue, pushing the equilibrium to the
left. When solutions were cooled the diluted solution turned almost completely clear/purple and
the other a lighter shade of blue (see table 1) pushing the equilibrium to the right side of the
reaction.. Heat is considered a product of this reaction, an exothermic reaction.