So, we were taught in lab how to identify a couple of cations and anions through elimination and confirmatory tests. I was wondering, however—how would this work if the test solution were made up of multiple ions?

For example, calcium and zinc would form a white precipitate, respectively, if you add $\ce{NaOH}$. In excess, zinc would dissolve; calcium would not. $\ce{Fe^3+}$ would form a red precipitate.

In a test solution with these three in it, I would assume that there would be red precipitate and white precipitate if you add $\ce{NaOH}$, is that right? And if you add in excess, only some of the white precipitate would dissolve … or something like that. How would you effectively go about the process of identifying the ions?

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    $\begingroup$ I'm pretty sure you would have learnt about more different possibilities of identifying the cations in solution (or not). Specifically for $\ce{Ca^2+}$, there is a qualitative analysis method that works independently of all other ions being there or not there. Are you, by any chance, in a practical course that has a nickname something like 'ion lottery'? $\endgroup$ – Jan Oct 5 '15 at 11:35
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    $\begingroup$ Eh... this is just how qualitative analysis is taught at a more basic level. Precipitation with NaOH or NH3. Obviously it's rather flawed. @OP you're right this is a rudimentary (and therefore poor) way of identifying ions. People write textbooks on these stuff. Do a google search for "Vogel inorganic QA" if you're interested. $\endgroup$ – orthocresol Oct 5 '15 at 14:23

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