Thread: How do you determine the difference between hydroxides, chlorides and carbonate soutions?

I need to do different experiments to determine the identity of 9 unknown solutions which then are made into another compound. It is a mixture of 2 of unknown substances. Will adding phenal red identify a hydroxide by turning it pink?

if you mean phenol red, adding it to a basic solution would make it re, but CO3- is also a base, and would react as well. Test for CO3- first, and then use the OH- test.

If you know that you have only chlorides, hydroxides and carbonates, you can use the folowing procedure:

Cl- test:
Take out a small sample, and put it into a test tube, then add a few drops of AgNO3, if there is a precipitate, and it is white, you have chlorides in your sample.

CO3- test:
Using a gass test tube, you put ca 0,5 mL of a fresh sample in the outter tube, in the inner tube, you add a saturated solution of Ba(OH)2

Then you add 3 M H2SO4 to the sample in the outter tube, if there is coloration in the liquid surface (on the inner tube), or on the inner tube it self, you have CO3- in your substance.

To test for OH-, check pH, if it is hugely basic, OH- is likely,
Add a ZnSO4 solution dropwise into a test tube filled with your sample, a gray precipitate will form if you have OH- (Zn(OH2)), now add the ZnSO4 solution in exess, and the precipitate should dissolve, as the [Zn(OH)4]2- complex ion, if this is so, you have definitively OH- in your solution.