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Difficulty: MediumOxides of Carbon and Trioxocarbonate(IV) Salts

When carbon(IV) oxide gas is continuously bubbled through an aqueous suspension of calcium trioxocarbonate(IV), CaCO3\text{CaCO}_3, the white suspension gradually turns into a clear solution. What is the chemical formula of the soluble compound formed?

Answer: Ca(HCO3)2 / Ca(HCO_3)_2 / calcium hydrogen trioxocarbonate(IV) / calcium hydrogencarbonate

Answer

Ca(HCO3)2\text{Ca(HCO}_3\text{)}_2 (Calcium hydrogen trioxocarbonate(IV))
When carbon(IV) oxide gas is bubbled into limewater or a suspension of CaCO3\text{CaCO}_3, it initially forms a cloudy white precipitate of CaCO3\text{CaCO}_3. Upon continued bubbling of excess CO2\text{CO}_2, the CaCO3\text{CaCO}_3 reacts with water and CO2\text{CO}_2 to yield soluble calcium hydrogen trioxocarbonate(IV), Ca(HCO3)2\text{Ca(HCO}_3\text{)}_2, causing the cloudiness to disappear.

Step-by-Step Solution

1
Identify the reactants and the chemical transformation taking place when excess carbon(IV) oxide reacts with calcium trioxocarbonate(IV) in water.
Insoluble calcium trioxocarbonate(IV) (CaCO3\text{CaCO}_3) reacts with dissolved carbon(IV) oxide (CO2\text{CO}_2) and water (H2O\text{H}_2\text{O}) according to the chemical equation: CaCO3(s)+H2O(l)+CO2(g)→Ca(HCO3)2(aq)\text{CaCO}_3\text{(s)} + \text{H}_2\text{O(l)} + \text{CO}_2\text{(g)} \rightarrow \text{Ca(HCO}_3\text{)}_2\text{(aq)}.
The reaction converts the insoluble trioxocarbonate(IV) salt into soluble calcium hydrogen trioxocarbonate(IV), which dissolves to clear the solution.

Key Concept

Formation of soluble hydrogen trioxocarbonate(IV) from carbon(IV) oxide and trioxocarbonate(IV) salts
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Topics

Oxides of Carbon and Trioxocarbonate(IV) Salts

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