# Can we use silver nitrate to distinguish between chloride and carbonate salts?

Initially, we are given a solution containing two salts, they can be either carbonate or chloride salts (we do not know their composition initially).

Generally, $$\ce{AgNO3}$$ is used as a confirmatory test of $$\ce{Cl-}$$ (a white precipitate is obtained on adding silver nitrate to solution containing the chloride salt). Therefore, can we use this method to directly identify chloride in the solution or do we need to remove the possible carbonate ions to confirm the presence of chloride before performing the test as mentioned above?

$$\ce{NaCl + AgNO3 -> NaNO3 + \underset{white}{AgCl} \downarrow}$$

$$\ce{Na2CO3 + 2AgNO3 -> 2NaNO3 + \underset{brownish white}{Ag2CO3} \downarrow}$$

(A similar question may arise in the identification of bromide and iodide ions but I have ignored it for now as they are rarely asked in exams. Still I would appreciate it if someone could give an answer for this as well.)

The question has been asked mainly because silver nitrate test is generally taught to be performed without mentioning above precautions and it is also a very famous confirmative test. So answer is expected more (not only) from a laboratory technician than theorist.

• You should work on your English sentences a little bit anyway, If you are asking how to test for $Cl^-$ reliably then ,You can add dil. $HNO_3$ to move the equilibrium to the carbonic acid side through application of Le-Chatelier Principle so as to have minimal [${CO_3}^{2-}$]in the solution which would not bring about any unreliability in the confirmation of $Cl^-$ – Rishi Apr 30 at 14:34
• That is indirectly you are removing carbonate as $$\ce{2H^+ + CO3^{-2} -> H2O + CO2}$$ I am sorry but I am loose at grammer. – Jay Apr 30 at 16:09
• Yes, Moreover I think there will be some other ways as well for this but to me this is the simplest. – Rishi May 1 at 2:34
• My general understanding of your question is you are given sodium chloride and sodium carbonate and you are to react them with silver nitrate in order to distinguish them. Right? In that case, it might work. Silver carbonate becomes more and more yellow and brown when excess of silver nitrate is used. Silver chloride remains white. Also, silver carbonate is soluble in nitric acid whereas silver chloride is not. – Nilay Ghosh May 1 at 4:24