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Homework Help: Why does the precipitate dissolve, reappear, and then dissolve again?

  1. May 6, 2007 #1
    why does the precipitate dissolve, reappear, and then dissolve again??

    1. The problem statement, all variables and given/known data

    i have a chem lab due tuesday and was wondering if anyone may please help me on it!!

    the problem:
    Mix silver nitrate solution and hydrochloric acid solution. Product is a precipitate
    2. Add ammonoum hydroxide solution drop by drop. precipitate dissolves.
    3. Add hcl again. precipiate forms
    4. add sodium thiosulfate..precipitate dissolves.

    why does the precipitate dissolve, reappear, and then dissolve again??

    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. May 6, 2007 #2
    1. AgNO3 + HCl -> HNO3 + AgCl
    HNO3 is soluble, but AgCl isn't (see solubility rules), so it precipitates.

    2. AgCl + NH4OH -> AgOH + NH4Cl
    It dissolves? Really? :/

    3. AgOH + HCl -> AgCl + H2O
    AgCl is insoluble again, so it precipitates again.

    4. 2AgCl + Na2S2O3 -> Ag2S2O3 + 2NaCl
    Uhhh......

    Well, at least you have the equations :P.
     
  4. May 6, 2007 #3
    hey how does the equations get affected when i use
    1> 5mL of 0.1 M of silver nitrate solution mixed with 5mL of 0.1 M HCl.

    2. then added 6 M ammoniumn hydroxide solution, drop by drop

    3. then added 10 mL of 0.1 M HCl solution

    4. then added 5mL of .15 M sodium thiosulfate
     
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