Question

Aqueous solutions of Na2CO3 and Ca(NO3)2, 0.10 M each, are combined. A white precipitate is observed in the container after mixing. The precipitate is filtered and carefully rinsed with distilled water to remove other ions. A sample of the precipitate is added to 100 mL of 0.1 M NaCl. A second sample of the precipitate is then added to 100 mL of 0.1 M HCl. What would be observed in each case

Answer 1

Upon adding the precipitate to NaCl, no visible change would occur. Conversely, adding the precipitate to HCl would result in the precipitate dissolving with the evolution of carbon dioxide gas.

Step-by-step explanation:

When aqueous solutions of Na2CO3 (sodium carbonate) and Ca(NO3)2 (calcium nitrate) are combined, a white precipitate of calcium carbonate (CaCO3) forms because it is insoluble in water. Adding the precipitate to 0.1 M NaCl would show no visible reaction because NaCl and CaCO3 are both soluble in water and no further precipitation would occur. In contrast, adding the precipitate to 0.1 M HCl would result in the dissolution of the precipitate with the release of carbon dioxide gas, because calcium carbonate reacts with hydrochloric acid to form soluble calcium chloride, water, and carbon dioxide gas.

The balanced equations would be:

• For NaCl addition: No reaction, the precipitate remains unchanged.
• For HCl addition: CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)↑ (precipitate dissolves)

Answer 2

The question is incomplete. Here is the complete question.

Aqueous solutions of
`Na_(2)CO_(3)` and
`Ca(NO_(3))_(2)`, 0.10 M each, are combined. A white precipitate is observed in the container after mixing. he precipitate is filtered andcarefully rinsed with distilled water to remove other ions. A sample of the precipitate is added to 100 mL of 0.1 M NaCl. A second sample of the precipitate is then added to 100 mL of 0.1 M HCl. What would be observed in each case?

Observation upon Observation upon

addition of precipitate addition of precipitate

to NaCl(aq) to HCl(aq)

(A) additional precipitates forms no visible reaction occurs

(B) no visible reaction occurs gas is produced and some precipitate dissolves

(C) no visible reaction occurs no visible reaction occurs

(D) additional precipitates forms gas is produced and some

precipitate dissolves

Answer: (B) No visible reaction occurs; Gas is produced and some precipitate dissolves

Step-by-step explanation: When aqueous solutions of
`Na_(2)CO_(3)` and
`Ca(NO_(3))_(2)` are combined, it reacts according to the following balanced equation:

`Na_(2)CO_(3)+Ca(NO_(3))_(2)` →
`CaCO_(3)_((s))+2NaNO_(3)_((aq))`

forming calcium carbonate (
`CaCO_(3)`), which, as it is insoluble in water, precipitates as a solid of the color white. This process is Precipitation and this reaction is a Precipitation Reaction.

When calcium carbonate reacts with NaCl it produces:

`CaCO_(3)+2NaCl` →
`CaCl_(2)+Na_(2)CO_(3)`

Now, calcium chloride is an inorganic compound very soluble in water, so, in this reaction, there are no precipitate and no visible reaction occurs.

When
`CaCO_(3)` reacts with hydrochloridric acid, the balanced reaction is

`CaCO_(3)+2HCl` →
`CaCl_(2)+H_(2)CO_(3)`

which, also produces calcium chloride and carbonic acid.

Both are soluble in water but, when carbonic acid is in an "aqueous state", carbonic acid, it dissociates, forming carbon dioxide and water. Therefore, gas is produced and some precipitate dissolves.

In conclusion, sentence B is the correct alternative.