# Homework Help: AgCl back to AgNO3

1. May 2, 2012

### zzac

1. The problem statement, all variables and given/known data
In a titration lab we had water in it with Na2Cr04 and used AgNO3 to precipitate the Cl ions in the water and thus determine the amount of chlorine in the water. We were then left with AgCl in the beaker and poured it into a waste beaker. Now our teacher wants us to figure out how to convert the AgCl back to AgNO3. I have some ideas but not sure if they will work.

2. Relevant equations
AgCl + ??? -> AgNO3
ksp of agcl= 1.8E-10, ksp of hcl = 1.1E-11, ksp cucl= 1.6E-7

3. The attempt at a solution
I figured that cuno3 could potentially remove the cl by the copper bonding with it. Then if a preciptiate forms and HNO3 and then have the NO3 bond with ag to get agno3. Again not too sure and any help much appreciated.

2. May 2, 2012

### Tecless

Erm Nitric acid?

AgCl + HNO3 ----> AgNO3 + HCl ?

Looks bout right :)

3. May 2, 2012

### zzac

I thought so too, but apparently silver chloride is insoluble in water and acids. I think I have to to something like form a precipitate with the chloride and then filter out and then add N03, I am more confused about how to form the precipitate.

4. May 3, 2012

### Staff: Mentor

You can dissolve AgCl complexing it.

Note that it is a known problem, for ideas google for reclaiming silver from the spent photographic fixer.

5. May 3, 2012

### zzac

AgCl + NH4Oh = AgOH + NH4Cl
AgOH = Ag2O
Ag2O is a precipitate, so filter out
Then: Ag20 + HNO3 = AgNO3 + H2O

6. May 3, 2012

### Staff: Mentor

You can either test the idea adding ammonia solution to the AgCl precipitate, or calculate the equilibrium using known values of solubility product.

IMHO neither approach is going to yield any success.

7. May 13, 2012

### zzac

In case anyone wanted to know the ammonia didn't work in the lab but when NaOH + H20 was mixed with AgCl(s) a precipitate formed. Then used vacuum filtration to separate precipitate then added the nitric acid which produced AgNO3.