I did a lab in my Chemistry 12 class, but I don't really understand equilibrium and cannot explain why it happened. CuSO4<=>Cu 2+ +SO4 2- We added NH3 into CuSO4 solution, and it turned lighter blue then turned to darker blue as we added more NH3 into it. Then, we added 1M HCl which made the solution clear, and there were blue specks sitting on the bottom of the test tube.  I have to show that what was the stress to this equilibrium and which way the equilibrium system shifted (either left or right). And stress would be increased/decreased temperature, increased/decreased product, increased/decreased reactant, increased/decreased pressure.

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From your question, I believe that the primary purpose of this lab is to demonstrate and understand Le Chatelier's principle (which is essentially equilibrium) and the concept of complex ion formation.

In your case, you are starting out with a copper sulfate (CuSO4) solution and adding ammonia (NH3) to it. Remember that NH3 is a weak alkaline/base which produces hydroxide ion in water:
NH3 + H2O <==> NH4(+) + OH(-)
Also, copper sulfate is an ionic solid that dissociates in water:
CuSO4 + H2O ==> Cu^2+ (aq) + SO4 ^2+ (aq)
Adding the NH3 will give you precipitate of...

(The entire section contains 310 words.)

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