I am confused about some post lab questions i need to answer about a lab I did on Le Chatelier’s Principle. Given: Pb2+ + 2 I PbI2 Pb2+ + 2 OH…

I am confused about some post lab questions i need to answer about a lab I did on Le Chatelier’s Principle.

Given:

Pb2+  +  2 I ‐  ⇌  PbI2

Pb2+  +  2 OH‐  ⇌  Pb(OH)2

Procedure:

a. Mix 5 drops Pb(NO3)2 and 5 drops KI in a test tube. Swirl/stir to mix thoroughly. Record observations. b. Add enough 0.1M NaOH to cause a change. Swirl/stir to mix thoroughly. Record observations. c. Add enough HNO3 to cause a significant change. Swirl/stir to mix thoroughly. Record observations. 

observation info: for part A, when we combined Pb(NO3)2 with KI, a clear liquid and yellow precipitate formed. For part B, when we added NaOH until a change, the precipitate turned white. for part C, when we added HNO3 until a change, the precipitate turned yellow and the solution a clear yellow.

2. Describe the change observed when sodium hydroxide is added in step b (step b. Add enough 0.1M NaOH to cause a change.  Swirl/stir to mix thoroughly) and explain why this change is consistent with Le Chatelier’s principle. {Note – to explain in terms of Le Chatelier’s principle means to explain the new change in conditions (in terms of the relative amounts of substance on both sides of the reaction equilibrium), what direction the equilibrium possibly shifted (toward left/reactants or right/products), and how this shift is done in terms of appearance/disappearance of substances.  If more than one equilibrium state is affected explain all conditions and shifts.}

3. Describe the change observed when nitric acid is added in step c and explain why this change is consistent with Le Chatelier’s principle.

I don’t really understand how my observations will tell me if the reactions are consistent with Le Chatelier’s principle and the reaction shifts to achieve equilibrium after being disturbed and how to tell which way the reaction shifts… Thanks!

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