Why must the silver nitrate test for chloride ions be done in an acidified solution?

1 Answer
Sep 1, 2016

Answer:

Because silver, like most of the heavier metals, forms an insoluble hydroxide.

Explanation:

In order to determine the presence of the halide, competing equilibria must be taken into account. Silver forms an insoluble hydroxide, which is probably a hydrous oxide. When #pH# is lowered from #7#, this competing equilibrium is removed, any chloride will precipitate as a curdy white solid as #AgCl#, as a lemon-yellow solid as #AgBr#, and as a bright yellow solid as #AgI#.

The acid of choice would be #HNO_3(aq)#. Why do we use this acid and not say #HCl(aq)# or #HBr(aq)#?