By which of the following method, `H_2O_2` cannot be synthesised?

Options

A. Addition of `H_2SO_4` on `BaO_2`
B. Addition of `H_2SO_4` on `PbO_2`
C. Aerial oxidation of 2-ethyl anthraquinol
D. Electrolysis of `(NH_4)_2SO_4` at a high current density.

Answer

To determine which method cannot be used to synthesize hydrogen peroxide (H₂O₂), let's analyze each option provided in the question step by step.

### Step 1: Analyze the first method - Addition of H₂SO₄ on BaO₂

When sulfuric acid (H₂SO₄) is added to barium peroxide (BaO₂), the reaction produces barium sulfate (BaSO₄) and hydrogen peroxide (H₂O₂). The balanced reaction can be represented as:

\[ \text{BaO}_2 + \text{H}_2\text{SO}_4 \rightarrow \text{BaSO}_4 \downarrow + \text{H}_2\text{O}_2 \]

**Conclusion:** This method can synthesize H₂O₂.

**Hint:** Look for the formation of H₂O₂ in the products of the reaction.

### Step 2: Analyze the second method - Addition of H₂SO₄ and PbO₂

When sulfuric acid (H₂SO₄) reacts with lead dioxide (PbO₂), the reaction produces lead sulfate (PbSO₄), water (H₂O), and oxygen (O₂). The reaction can be represented as:

\[ \text{PbO}_2 + \text{H}_2\text{SO}_4 \rightarrow \text{PbSO}_4 + \frac{1}{2}\text{O}_2 + \text{H}_2\text{O} \]

**Conclusion:** This method does not produce H₂O₂; instead, it produces water and oxygen.

**Hint:** Identify the products of the reaction and check if H₂O₂ is formed.

### Step 3: Analyze the third method - Aerial oxidation of 2-ethyl anthraquinol

In this method, 2-ethyl anthraquinol undergoes aerial oxidation to form hydrogen peroxide. The reaction involves the conversion of hydroxyl groups to carbonyl groups, leading to the formation of H₂O₂.

**Conclusion:** This method can synthesize H₂O₂.

**Hint:** Consider how oxidation reactions can lead to the formation of peroxides.

### Step 4: Analyze the fourth method - Electrolysis of (NH₄)₂SO₄ at high current density

During the electrolysis of ammonium sulfate ((NH₄)₂SO₄), hydrogen ions (H⁺) are produced at the cathode, and the ammonium sulfate ions undergo hydrolysis to produce H₂O₂. The overall reaction can be summarized as:

\[ \text{Electrolysis of } (NH_4)_2SO_4 \rightarrow H_2O_2 \text{ (among other products)} \]

**Conclusion:** This method can synthesize H₂O₂.

**Hint:** Look for electrolysis reactions that yield hydrogen peroxide as a product.

### Final Conclusion

After analyzing all the methods, the method by which H₂O₂ cannot be synthesized is:

**Answer:** Addition of H₂SO₄ and PbO₂ (produces H₂O instead of H₂O₂).