Asolution containing a mixture of metal cations was treated with dilute hcl and no precipitate formed. next, h2s was bubbled through the acidic solution. a precipitate formed and was filtered off. then, the ph was raised to about 8 and h2s was again bubbled through the solution. a precipitate again formed and was filtered off. finally, the solution was treated with a sodium carbonate solution, which resulted in no precipitation. which metal ions were definitely present, which were definitely absent, and which may or may not have been present in the original mixture?

Explanation:

If you follow the statements carefully the only ions you can rule out as being "Definitely not present" are: Cr3+, Fe3+, and Zn2+ . The rest of the ions should be categorized under "Possibly present", as we cannot determine if any of the ions are "Definitely present".

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).