Hi chemistry enthusiasts! I am working on my scholarship exam practice. I believe this exam assumes high school + first year university knowledge although the standard may be varied across the world. And I'm not quite sure what I did wrong. Could you please have a look?

There is an aqueous solution containing Cu2+ and Pb2+ ions. The most suitable reagent to precipitate one of the two ions from the solution is (1) nitric acid (2) sodium carbonate (3) sulfuric acid (4) hydrogen sulfide

I picked answer (4) hydrogen sulfide because I think that it will react with copper (II) ions and will precipitate out. However, the correct answer is (3) sulfuric acid. How is this answer correct and what did I do wrong for hydrogen sulfide. Your advice will be much appreciated!


1 Answer 1


If you read the question carefully, they wish to precipitate only one ion, either copper or lead. The facts that must be in your mind are:

(i) Lead sulfate is insoluble in water but copper sulfate is. (ii) Both lead sulfide and copper sulfide are water insoluble.


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