A solution containing a mixture of metal cations was treated with dilute HCl and a precipitate formed. The solution was filtered, and H2S was bubbled through the acidic solution. A precipitate again formed and was filtered off. Then, the pH was raised to about 8 and H2S was again bubbled through the solution. This time, no precipitate formed. Finally, the solution was treated with a sodium carbonate solution, which resulted in the formation of a precipitate.
Classify the metal ions based on whether they were definitely present, definitely absent, or whether it was possible they were present in the original mixture.

Cd²⁺, Sb³⁺, Hg²⁺, Pb²⁺, Ba²⁺, Zn²⁺, Fe²⁺, Cr³⁺, Sn⁴⁺, Li⁺, Mg²⁺, Hg₂²⁺, Ag⁺

One way in which the useful metal copper is produced is by dissolving the mineral azurite, which contains copper(ii) carbonate, in concentrated sulfuric acid. the sulfuric acid reacts with the copper(ii) carbonate to produce a blue solution of copper(ii) sulfate. scrap iron is then added to this solution, and pure copper metal precipitates out because of the following chemical reaction: (s) (aq) (s) (aq) suppose an industrial quality-control chemist analyzes a sample from a copper processing plant in the following way. he adds powdered iron to a copper(ii) sulfate sample from the plant until no more copper will precipitate. he then washes, dries, and weighs the precipitate, and finds that it has a mass of .