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Testing for ammonia

  1. May 4, 2013 #1

    I'm looking at a question which asks how one can test for ammonia in


    The answer says that you add sodium hydroxide, and get

    [NH4]2Fe[SO4]2 + 2 NaOH -> [NH4]2Fe(OH)2 + 2 NaSO4

    This is what I don't get: it then says you test the ammonia gas with litmus paper, or with HCL. In the former case, the litmus paper turns blue, and in the latter, you get white smoke.

    My two questions: I know ammonia is alkaline, but how is [NH4]2Fe(OH)2 a gas? Secondly, why do you get white smoke when you add HCL?

    Thanks for your input.
    Last edited: May 4, 2013
  2. jcsd
  3. May 4, 2013 #2


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    Staff: Mentor

    Your reaction equation is wrong.

    It is about NH4+ being neutralized by NaOH to produce conjugate base.
  4. May 4, 2013 #3
    Hi Borek

    I'm beginning to see how it's correct...that the ammonia dissociates in water so it can react.

    Could you please describe what the correct equation is? We haven't looked at conjugate bases, could you elaborate?

  5. May 4, 2013 #4


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    Staff: Mentor

    Ammonia evolves after being neutralized by the strong base:

    NH4+ + OH- → NH3↑ + H2O
  6. May 4, 2013 #5
    I see. From what I understand, 'evolves' means that it turns into gas?
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