On heating manganese dioxide with conc. HCI, which of the following is evolved?

Options

A. Chlorine
B. Oxygen
C. Chlorine monoxide
D. Hydrogen

Explanation

To solve the question of what gas is evolved when manganese dioxide (MnO2) is heated with concentrated hydrochloric acid (HCl), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**: The reactants in this reaction are manganese dioxide (MnO2) and concentrated hydrochloric acid (HCl).

2. **Understand the Reaction**: Manganese dioxide is known to be a strong oxidizing agent. When it reacts with concentrated HCl, it can oxidize the hydrochloric acid.

3. **Write the Chemical Reaction**: The balanced chemical equation for the reaction can be written as:
\[ \text{MnO}_2 + 4 \text{HCl} \rightarrow \text{MnCl}_2 + 2 \text{H}_2\text{O} + \text{Cl}_2 \]
In this reaction, manganese dioxide reacts with hydrochloric acid to produce manganese chloride (MnCl2), water (H2O), and chlorine gas (Cl2).

4. **Identify the Evolved Gas**: From the balanced equation, we can see that chlorine gas (Cl2) is produced as one of the products of the reaction.

5. **Conclusion**: Therefore, the gas evolved when manganese dioxide is heated with concentrated hydrochloric acid is chlorine (Cl2).

### Final Answer:
The gas evolved is **chlorine (Cl2)**.

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