No precipitate formed when an aqueous solution of NaCl or Na2SO4 was added to the sample solution. A precipitate formed when the sample solution was made basic with NaOH. Which ion(s) are present in the sample soluiton?

[Hg2]2+
[Ba]2+
[Mn]2+

I know that all three are not, but how do I figure out what is?

Hg2^+2 isn't there because it would form a ppt of Hg2Cl2 with NaCl.

Ba^+2 isn't there because it would form a ppt with Na2SO4 of BaSO4.
That only leaves one possibility.
Mn^+2 + 2OH^- ==> Mn(OH)2

Well, seems like we have a classic case of "No-precipitate-itis!" The fact that no precipitate was formed when NaCl or Na2SO4 was added to the sample solution means that chloride (Cl-) and sulfate (SO42-) ions are not present. However, when the sample solution gets a little too basic with NaOH, a precipitate forms. This tells us that the hydroxide ions (OH-) are reacting with a metal cation to form an insoluble hydroxide compound.

So, out of the three options given, the only one that could be causing this is the manganese (Mn2+) ion. Looks like Mn2+ is a bit of a diva and can't handle too much base! Keep in mind that this conclusion is made purely based on the information given and some hilarious guesswork.

To determine which ion(s) are present in the sample solution, you can use the information given about the reactions with NaCl, Na2SO4, and NaOH.

1. When an aqueous solution of NaCl (sodium chloride) is added to the sample solution and no precipitate forms, it suggests that there are no chloride ions (Cl-) in the sample solution, ruling out [Hg2]2+ as a possible ion.

2. When an aqueous solution of Na2SO4 (sodium sulfate) is added to the sample solution and no precipitate forms, it indicates that there are no sulfate ions (SO42-) in the sample solution, ruling out [Ba]2+ as a possible ion.

3. However, when the sample solution is made basic with NaOH (sodium hydroxide), a precipitate forms. This suggests that there must be cations present in the sample solution that react with hydroxide ions (OH-) to form an insoluble hydroxide precipitate.

Based on the given options, the possible ion(s) present in the sample solution is [Mn]2+.

To determine which ion(s) are present in the sample solution, we need to analyze the reactions that occurred when different substances were added.

1. When an aqueous solution of NaCl was added:
If no precipitate formed, it means that neither Cl- nor Na+ ions reacted with any species in the sample solution. Therefore, we can conclude that the ions present in the sample solution are not derived from NaCl.

2. When an aqueous solution of Na2SO4 was added:
Again, no precipitate formed. This implies that neither SO42- nor Na+ ions reacted to form an insoluble compound. Thus, the ions present in the sample solution are not derived from Na2SO4.

3. When the sample solution was made basic with NaOH:
A precipitate formed during this reaction, indicating the presence of specific ions in the sample solution that reacted with OH- ions. Let's consider each possibility:

[Hg2]2+ (Mercury):
Mercury(II) ions are known to form insoluble hydroxides when reacted with an alkaline solution. If [Hg2]2+ were present in the sample solution, a precipitate would have formed. However, since no precipitate formed, we can exclude the presence of mercury ions.

[Ba]2+ (Barium):
Barium(II) ions also form insoluble hydroxides when reacted with a base. Therefore, if [Ba]2+ were present in the sample solution, a precipitate would form. However, no precipitate was observed, so we can eliminate the possibility of barium ions.

[Mn]2+ (Manganese):
Manganese(II) ions are not known to form insoluble hydroxides. Therefore, they do not react with NaOH to form a precipitate. Since a precipitate formed when the sample solution was made basic, we can conclude that the ions present in the solution are likely manganese(II) ions.

In summary, based on the given observations, the most probable ion present in the sample solution is [Mn]2+ (Manganese).