When aqueous solutions of baking soda (NaHCO_3) and calcium chloride (CaCl_2) are combined, which of the following observations is most likely?

• A. The solution turns blue, indicating the formation of a complex ion.
• B. No visible change occurs; all substances remain dissolved.
• C. A white precipitate forms due to the production of calcium carbonate (CaCO_3).
• D. A gas is released, producing bubbles in the solution.

Answer: (C)

Verified step by step guidance

1. Identify the ions present when the two compounds dissolve in water: baking soda (NaHCO_3) dissociates into Na\^{+} and HCO_3\^{-}, and calcium chloride (CaCl_2) dissociates into Ca\^{2+} and Cl\^{-}.
2. Consider the possible reactions between these ions. Calcium ions (Ca\^{2+}) can react with bicarbonate ions (HCO_3\^{-}) to form calcium carbonate (CaCO_3), which is known to be insoluble in water.
3. Write the net ionic equation for the precipitation reaction: Ca\^{2+} + 2 HCO_3\^{-} \rightarrow CaCO_3 (s) + CO_2 (g) + H_2O. This shows the formation of solid calcium carbonate and release of carbon dioxide gas.
4. Determine the physical observation expected from this reaction. The formation of solid CaCO_3 will appear as a white precipitate in the solution.
5. Conclude that the most likely observation when mixing these solutions is the formation of a white precipitate due to calcium carbonate, rather than color change or gas bubbles alone.