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Homework Help: Lewis Acid / Base Reactions

  1. Nov 21, 2013 #1
    I'm having trouble understanding the following reactions we did in lab and I am not sure our data is very good.

    CuSO4 + NaOH yields a blue precipitate. Which I understand is Cu(OH)2. I get this.

    Next we add NH3 to the solution above and nothing obvious changes. I think the precipitate may have dissolved. What is happening here?

    After this we created a new solution but this time we added CuSO4 to the NH3 and then we added the NaOH. Yet again we just got a blue solution and I am not sure what happened.

    Finally we just mixed NH3 and CuSO4 which produced a light blue precipitate.

    Can someone please explain to me what is going on in all three reaction above.
  2. jcsd
  3. Nov 28, 2013 #2


    User Avatar

    Staff: Mentor

    You are right about copper hydroxide.

    Copper hydroxide dissolves in ammonia, producing tetraammine copper complex. When you add small amount of ammonia initially hydroxide precipitates, when you add more ammonia precipitate dissolves and solution becomes dark blue.
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