gayleegoo

I talked to my teacher and he said no HF so i was actually in the process of creating a lab based on what you just said. I do need to clarify something though; based on the solubility rules, if you add sulfuric acid to Mg2+ wouldn't you get and aqueous sln of MgSulfate and the other sulfates would form a precipate (this is based on the Mg2+ being selectively soluble with Sulfate). I guess I'm just confused about how the addition of SrSulfate will help. Could you clarify?

Thanks. That was helpful. Here is what I have figured out so far. Here is the general scheme: 1.) rock (containing Mg 2+) + HF (able to dissolve rocks)---->MgF2 (and if Ca, Sr, and Ba are in the rock they will precipitate as well) 2.) To be sure that the above mentioned ions are not part of the MgF2 precipitate (MgF2+ precipitate) + Sulfate ---->MgSulfate(aq) + possible Ca, Sr, Ba,sulfate precipitate 3.) I would then discard the precipitate and use the aq MgSulfate sln to determine the initial Mg content in the rock. Does this seem plausible to you? Also, do you have any suggestions as to how I can determine the Mg content from the MgSulfate aqueous solution?

I'm working on designing a lab on how to determine the Mg 2+ content in a sample of rock. Does anyone have any ideas as to how this can be done?