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

[billabonger77]

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

Homework Statement

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??

Homework Equations

The Attempt at a Solution

 

[Noober]

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.

 

[billabonger77]

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