Sulphuric acid is considered as the king of chemicals. The prosperity of any country is measured by the amount of sulphuric acid it consumes. Sulphuric acid is, thus, a substance of very great commercial importance as it used practically ine every important industry. This is due to the following properties of sulphuric acid :
(a) acidic nature
(b) oxidising nature
(c) dehydrating nature
(d) sulphonation.
only carbon is obtained when concentrated `H_2 SO_4` is added to

Options

A. Formic acid
B. Cane sugar
C. Oxalic acid
D. Ethyl alcohol

Explanation

To determine which reactant yields only carbon when concentrated sulfuric acid (H₂SO₄) is added, we will analyze the reactions of each given option with concentrated sulfuric acid.

### Step-by-Step Solution:

1. **Identify the Reactants:**
- The reactants provided are:
- A) Formic acid (HCOOH)
- B) Cane sugar (C₁₂H₂₂O₁₁)
- C) Oxalic acid (C₂O₄H₂)
- D) Ethyl alcohol (C₂H₅OH)

2. **Reaction with Formic Acid:**
- When formic acid reacts with concentrated H₂SO₄:
\[ \text{HCOOH} + \text{H}_2\text{SO}_4 \rightarrow \text{CO} + \text{H}_2\text{SO}_4 \cdot \text{H}_2\text{O} \]
- The product formed is carbon monoxide (CO), not elemental carbon (C).
- **Conclusion:** Option A is incorrect.

3. **Reaction with Cane Sugar:**
- When cane sugar reacts with concentrated H₂SO₄:
\[ \text{C}_{12}\text{H}_{22}\text{O}_{11} + \text{H}_2\text{SO}_4 \rightarrow \text{C} + \text{CO}_2 + \text{H}_2\text{O} + \text{SO}_2 \]
- This reaction produces elemental carbon (C) along with carbon dioxide (CO₂), water (H₂O), and sulfur dioxide (SO₂).
- **Conclusion:** Option B is correct.

4. **Reaction with Oxalic Acid:**
- When oxalic acid reacts with concentrated H₂SO₄:
\[ \text{C}_2\text{O}_4\text{H}_2 + \text{H}_2\text{SO}_4 \rightarrow \text{No Carbon Produced} \]
- This reaction does not yield elemental carbon.
- **Conclusion:** Option C is incorrect.

5. **Reaction with Ethyl Alcohol:**
- When ethyl alcohol reacts with concentrated H₂SO₄:
\[ \text{C}_2\text{H}_5\text{OH} + \text{H}_2\text{SO}_4 \rightarrow \text{C}_2\text{H}_4 + \text{H}_2\text{O} \]
- This reaction produces ethene (C₂H₄) and water (H₂O), but no elemental carbon.
- **Conclusion:** Option D is incorrect.

### Final Answer:
The only reactant that produces elemental carbon when concentrated sulfuric acid is added is **B) Cane Sugar**.