[ChargePositive]

Hello, I think I may have come up with a procedure for a chemistry experiment to determine the chloride concentration in content.

Titrant: AgNO3

Materials: Na2CrO4 (Indicator)
CaCO3

PROCEDURE:
1) Pour known solution ml of unknown concentration solution (CaCO3) into a flask with a few drops of indicator. (Na2Cr04)

2) Full burrete with titrant (AgNO3)

3) Slowly use burette to pour titrant (AgNO3) into a flask with CaCO3 until color change.

4) Note the amount of titrant used to perform calculation to find chloride concentration.


THE QUESTION IS:
Is the procedure correct for finding the concentration of Chloride in solution? If not, what have I done wrong? Thanks for any help/advice.

[Arkcon]

Seems like a reasonable plan.  Assuming the CaCO3 solution contains some chloride, you should get a result.  You might want to say, what color change you expect to get.  As in, from what color to what color.  Note: when we do a titration, a color change isn't definitive.  For example, titating an acid with a base using phenolphthalein:  Acid, with phenolpthalein in it, is clear.  With an abundance of base in it, its bright magenta.  We don't add base until it goes that far.  We add base until its "faintly pink" or "pink color that won't disappear after 15 sec of swirling."  The color change in your case will be even more subtle.

[Borek]

Pour known solution ml of unknown concentration solution (CaCO3)

Solution of insoluble (well, very weakly soluble) CaCO₃?

Slowly use burette to pour titrant (AgNO3) into a flask with CaCO3 until color change.

I don't remember numbers so I can be wrong here, but there is an obvious possible interference from the precipitation of Ag₂CO₃. It can either precipitate with the AgCl or instead of Ag₂CrO₄. Different problems but the net effect is the same - unreliable determination result. Have you checked if the interference is possible? Perhaps there is a way of preventing it?

Also see http://www.titrations.info/precipitation-titration-argentometry-chlorides-Mohr