Concentrated `H_(2)SO_(4)` cannot be used to prepare HBr from NaBr , because it ,

Options

A. If both (A) and (R) are true and (R) is the correct explanation of (A)
B. if both (A) and (R) are true but (R) is not correct explanation of (A)
C. If (A) is true but (R) is false
D. If (A) is false but (R) is false

Explanation

To understand why concentrated H₂SO₄ cannot be used to prepare HBr from NaBr, let's break down the reasoning step by step.

### Step 1: Identify the Reactants
We start with two substances:
- Sodium bromide (NaBr)
- Concentrated sulfuric acid (H₂SO₄)

### Step 2: Understand the Reaction
When NaBr is treated with concentrated H₂SO₄, we would expect a reaction to occur. The expected reaction would be:
\[ \text{NaBr} + \text{H}_2\text{SO}_4 \rightarrow \text{NaHSO}_4 + \text{HBr} \]

### Step 3: Analyze the Properties of H₂SO₄
Concentrated sulfuric acid is known to be a strong oxidizing agent. This means it has the ability to accept electrons from other substances, thereby oxidizing them.

### Step 4: Analyze the Properties of HBr
HBr, on the other hand, is a strong reducing agent. This means it can donate electrons and reduce other substances.

### Step 5: Determine the Outcome of the Reaction
When HBr is formed in the presence of concentrated H₂SO₄, HBr can reduce the sulfuric acid:
\[ \text{HBr} + \text{H}_2\text{SO}_4 \rightarrow \text{Br}_2 + \text{SO}_2 + \text{H}_2\text{O} \]

In this reaction, HBr is oxidized to bromine (Br₂) while sulfuric acid is reduced to sulfur dioxide (SO₂).

### Step 6: Conclusion
Since HBr reduces sulfuric acid, the reaction does not proceed as intended to produce HBr from NaBr and concentrated H₂SO₄. Instead, HBr is consumed in the reaction, leading to the conclusion that concentrated H₂SO₄ cannot be used to prepare HBr from NaBr.

### Final Statement
Thus, the assertion is correct: concentrated H₂SO₄ cannot be used to prepare HBr from NaBr because HBr acts as a reducing agent and reduces H₂SO₄ instead of allowing the formation of HBr.