How to Determine the Percent Mass of a Mystery Alkali Carbonate in a Reaction?

[gaylateacher]

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I have a mystery alkali carbonate. I need to react it with sulfuric acid. When this occurs I know the products are carbon dioxide, water, ions of the mystery metal in solution and ions of sulfate in the solution. My question is how do I find the percent mass of the carbonate in the reactant if I cannot capture and measure the volume of the carbon dioxide product? I know I need to identify the alkali metal but I do not know how? Any suggestions?
gaylateacher

 

[chem_tr]

I think you are not doing the correct thing, first you don't know what metal you are using, and second, you are trying to find carbonate percentage in the sample. However, you may do it titrimetrically, by starting with phenolphthalein (and preferably, a known amount of standardized base added) and ceasing the titration whenever the purple color disappears; of course titration approach needs multiple tries to reach more precise results.

Then you may try calculating the metal percentage from the sample weight. This may give you an idea.

 

[lalbatros]

Could you not weight before and after reaction?
The difference should be the CO2.

You did not mention if your carbonate is pure.
Assuming it is, then it should be easy to identify the metal.
(assuming complete decomposition)

Another way I could imagine is without sulfuric acid, by putting the alkali carbonate in a oven at high temperature. Weight loss by decarbonatation should give you the result.


I am not a chemist, sorry if I am telling you stupid things.