Question

When CO\(_2\) is passed through solution of calcium hydroxide, which one of the following compound is precipitated?

• A. Ca(HCO\(_3\))\(_2\)
• B. CaO
• C. CaCO\(_3\)
• D. Ca(OH)\(_2\)

Hint:

Excess CO\(_2\) gives soluble Ca(HCO\(_3\))\(_2\), clearing the solution.

Answer 1

The Correct Option is C

To determine which compound is precipitated when CO₂ is passed through a solution of calcium hydroxide, we need to understand the chemical reaction that occurs in this process.

Calcium hydroxide, Ca(OH)₂, is a basic compound. When carbon dioxide (CO₂) is bubbled into a solution containing calcium hydroxide, the following reaction takes place:

\[\text{Ca(OH)}_{2(aq)} + \text{CO}_{2(g)} \rightarrow \text{CaCO}_{3(s)} + \text{H}_2\text{O}_{(l)}\]

In this reaction, calcium carbonate, CaCO₃, is formed as a precipitate.

Let's analyze each of the given options:

1. Ca(HCO₃)₂: Calcium bicarbonate would require the dissolution of CO₂ in excess, leading to no immediate precipitation under normal conditions. It is typically stable in aqueous solution. Therefore, not precipitated.
2. CaO: Calcium oxide is not formed in this reaction as it would require a decomposition process, which isn't feasible with CO₂ addition alone.
3. CaCO₃: As confirmed by the reaction, calcium carbonate is the solid precipitate formed when CO₂ is added to a calcium hydroxide solution.
4. Ca(OH)₂: This is the reactant, not the product. Also, it is in solution already; hence, it will not precipitate upon the addition of CO₂.

Thus, the correct answer is CaCO₃.