Chemical Equlibrium of BaCrO4

  • Thread starter Paulham
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  • #1
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Homework Statement


Hi everyone,

I'm trying to finish my lab report but I'm stuck on this question and don't even know how to start it. Could anyone let me know how to board it or a starting clue?

I'm given these two equations

1. BaCrO4 (s) <---> Ba2+ (aq) + CrO42- (aq)

2. 2CrO42- (aq) + 2H+ (aq) <----> Cr2O72- (aq) + H2O (l)

Question: How would you precipitate BaCrO4 from a solution of Ba(NO3)2 and K2Cr2O7 ? And I need to show it in chemical equations.

Homework Equations




The Attempt at a Solution



I honestly have no clue...
 

Answers and Replies

  • #2
Bystander
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You're working on the chromate-dichromate equilibrium in another thread; can you apply that equilibrium to this problem?
 
  • #3
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Sure, if I knew how to that is...:)
 
  • #4
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Do you need low, or high concentration of CrO42- to precipitate BaCrO4?

How does concentration of CrO42- depend on pH? (That's a direct conclusion of the question you posted in another thread, changing pH shifts the CrO42-/Cr2O72- equilibrium; how?)
 
  • #5
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Hi,

I was just looking at that and this is what I came up with: so I would need a high concentration of CrO42- to precipitate BaCrO4 and I can increase the concentration of CrO42- by lowering the concentration of H+ by adding NaOH so it will neutralize the H+. This way my equilibrium will shift to the left forming more CrO42-. Then by adding Ba(NO3)2...the NO3 would be a spectator ion but Ba2+ would form the BaCrO4 precipitate because BaCr2O7 is more soluble...would that be right?
 
  • #6
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