Which gas is evolved when acids react with metal carbonates ?

Options

A. `CO_(2)`
B. `H_(2)`
C. `NH_(3)`
D. `O_(2)`

Explanation

To determine which gas is evolved when acids react with metal carbonates, let's analyze the reaction step by step.

### Step-by-Step Solution:

1. **Identify the Reactants**:
- When an acid reacts with a metal carbonate, the general formula can be represented as:
\[ \text{Acid} + \text{Metal Carbonate} \rightarrow \text{Salt} + \text{Water} + \text{Gas} \]

2. **Choose a Specific Example**:
- Let's take hydrochloric acid (HCl) and calcium carbonate (CaCO₃) as an example:
\[ \text{HCl} + \text{CaCO}_3 \rightarrow \text{CaCl}_2 + \text{H}_2\text{O} + \text{CO}_2 \]

3. **Identify the Products**:
- In this reaction, the products formed are:
- Calcium chloride (CaCl₂) - a salt
- Water (H₂O)
- Carbon dioxide (CO₂) - the gas evolved

4. **Conclusion**:
- From the reaction, we can conclude that the gas evolved when acids react with metal carbonates is **carbon dioxide (CO₂)**.

### Final Answer:
The gas evolved when acids react with metal carbonates is **carbon dioxide (CO₂)**.

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