`KBr`,on reaction with conc `H_(2)SO_(4)` give reddish brown gas which bleaches moist limus paper .The evolved gas is

Options

A. Bromine
B. Mixture of bromine and HBr
C. `HBr`
D. `NO_(2)`

Explanation

To solve the question regarding the reaction of KBr with concentrated H₂SO₄, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants:**
The reactants in the reaction are potassium bromide (KBr) and concentrated sulfuric acid (H₂SO₄).

2. **Understand the Reaction:**
When KBr reacts with concentrated H₂SO₄, the sulfuric acid acts as an oxidizing agent. This means it can oxidize bromide ions (Br⁻) to bromine gas (Br₂).

3. **Write the Initial Reaction:**
The initial reaction can be represented as:
\[ \text{KBr} + \text{H}_2\text{SO}_4 \rightarrow \text{KHSO}_4 + \text{HBr} \]
Here, potassium hydrogen sulfate (KHSO₄) and hydrogen bromide (HBr) are formed.

4. **Further Reaction of HBr:**
The hydrogen bromide (HBr) can further react with concentrated H₂SO₄, leading to the formation of bromine gas (Br₂) and other products:
\[ \text{HBr} + \text{H}_2\text{SO}_4 \rightarrow \text{Br}_2 + \text{H}_2\text{O} + \text{SO}_2 \]

5. **Identify the Evolved Gas:**
The reddish-brown gas produced in this reaction is bromine (Br₂), which is known for its characteristic color.

6. **Bleaching Effect on Litmus Paper:**
Bromine gas has bleaching properties, which means it can decolorize moist litmus paper, confirming the identity of the gas.

7. **Conclusion:**
Therefore, the evolved gas when KBr reacts with concentrated H₂SO₄ is bromine (Br₂).

### Final Answer:
The evolved gas is **Bromine (Br₂)**.