[baboom]

I added a about 0.5g of a chloride sample to a beaker and to this beaker I added a hundred mL of distilled water.  Than I added a few drops of nitric acid. Afterwards, I added a silver nitrate solution. I than heated the solution to about 90 degrees celcius to coagulate the precipitate.

When the mixture cooled I filtered the silver chloride salt.

Was it really necessary to add the nitric acid? The reaction would happen anyway without it, no?

[nj_bartel]

The reaction will occur without acid.  Unsure of reason, but I would think it's probably to oxidize something (not sure what).

[baboom]

 ok thanks nj for your reply!

[408]

Also possible it is to lower the pH, as any OH or (bi)carbonate species would precipitate with the AgCl, contaminating it, hurting any quantitative result.  Likely nitric was chosen for this task simply because sulfuric or hydrochloric would also precipitate with the Ag.

[baboom]

Thanks for your reply!
I am just wondering why any OH species form during the reaction, do you know?

[Borek]

I am with 408 here. Hydroxides of many metals are easily precipitated even from neutral solutions - there is no need for OH^- to be created during the reaction, just water hydrolyzis is often eneough. Adding acid to lower the pH makes it a non-issue.

[baboom]

Thanks guys!