Final answer:
The unknown solution forms precipitates with Na2SO4 and Na2CO3 but not with NaCl. Using solubility guidelines, the unknown solution might be Ba(NO3)2 or Sr(NO3)2, as barium and strontium form insoluble sulfates and carbonates.
Step-by-step explanation:
The student is asked to determine the possible identity of an unknown solution based on its precipitation reactions with other solutions. The data indicates that the unknown solution forms a precipitate with Na2SO4 and Na2CO3, but not with NaCl. Using the solubility guidelines, which state that all nitrate salts are soluble while certain carbonates and sulfates form insoluble salts with specific cations, we can deduce the possible compounds.
Candidates for the unknown solution that would precipitate with Na2SO4 and Na2CO3 are those that form insoluble sulfates and carbonates. Barium nitrate (Ba(NO3)2), for instance, would form a precipitate with both these compounds, as barium sulfate (BaSO4) and barium carbonate (BaCO3) are insoluble. Strontium nitrate (Sr(NO3)2) would behave similarly.
Therefore, the compounds that might be the unknown solution are A) Ba(NO3)2 - Barium nitrate and C) Sr(NO3)2 - Strontium nitrate. Calcium nitrate (Ca(NO3)2), which forms a soluble sulfate and carbonate, can be excluded, as can the other options which do not form precipitates with either Na2SO4 or Na2CO3.