When fluoride is heated with conc. `H_2 SO_4` and `MnO_2` the gas evolved is

Options

A. `F_(2)`
B. SF
C. HF
D. None

Answer

To solve the question of what gas evolves when fluoride is heated with concentrated H₂SO₄ and MnO₂, we can break down the process step by step.

### Step 1: Understand the Reactants
- **Fluoride**: This refers to fluoride ions (F⁻) or compounds containing fluoride, such as sodium fluoride (NaF).
- **Concentrated H₂SO₄**: This is sulfuric acid, which is a strong acid and dehydrating agent.
- **MnO₂**: Manganese dioxide, which can act as an oxidizing agent.

### Step 2: Analyze the Reaction
When fluoride is heated with concentrated sulfuric acid and MnO₂, we need to consider the properties of fluoride. Fluoride is the most electronegative element and is very stable in its ionic form (F⁻).

### Step 3: Determine the Possible Products
- The reaction involves heating, which can lead to the release of gases.
- MnO₂ and concentrated H₂SO₄ are not strong enough to oxidize fluoride ions to fluorine gas (F₂) because fluoride is already in its most stable form.

### Step 4: Conclusion on Gas Evolution
Since fluoride cannot be oxidized to fluorine gas under these conditions, and no other gases are produced from the reaction of fluoride with concentrated sulfuric acid and MnO₂, we conclude that **no gas evolves**.

### Final Answer
The gas evolved is: **No one** (meaning no gas is evolved).