Will copper float in mercury

Answer 1

To answer this question, you really need to know which anions are being used with these metals. To predict precipitates, you must know all the different ions and how they can combine. A precipitate will form when a pair of the possible combinations is not soluble. Some Mercury salts are soluble and others are not, but mercury salts are not typically very soluble. Similarly, some copper salts are soluble, others are not, but they tend to be more soluble than mercury salts. So if you add two soluble copper and mercury salts together, there is a good chance that you will form a new INSOLUBLE mercury salt, and this will come out as a precipitate. Let me give an example. If you have copper(II) chloride (CuCl2) and you mix it with mercury(I) nitrate (HgNO3), both of which are soluble, then you will have the following ions floating around in solution: Cu2+, Cl-, Hg+, and NO3-. However, it turns out that HgCl is an insoluble compound. So each time these two ions bump into each other in the solution, they will form a precipitate due to the insolubility. However, both CuCl2 and Cu(NO3)2 are soluble, and so they will not precipitate. If instead you did the same thing but now used Cu(NO3)2 and Hg2SO4, no precipitate would form because both of those are soluble, and also so are CuSO4 and HgNO3. See the Web Links to the left of this answer for a table of solubilities.

Answer 2

No, copper will sink in mercury because copper is denser than mercury. Mercury has a lower density than copper, so when the two substances are put together, the copper will sink to the bottom.