`H_(2)C_(2)O_(4)` acts as an acid as well as an oxidizing agent. The correct statement (s) about `H_(2)C_(2)O_(4)` is /are .

Options

A. a) it forms two series of salts
B. b) equivalent weight of `H_(2)C_(2)O_(4)` as an acid for complete neutralisation and as an oxidant are same.
C. c) 100 ml of `0.1 ` `M` solution of `Ca(OH)_(2)` will be completely neutralized by 50 ml of `0.2 M H_(2)C_(2)O_(4)`
D. d) 100 ml of `0.1` M solution of `KMnO_(4)` (acid) will be completely reduced by 50 ml of 1 M `H_(2)C_(2)O_(4)`

Answer

To determine the correct statements about oxalic acid (H₂C₂O₄), we will analyze each statement step by step.

### Step 1: Understanding the properties of H₂C₂O₄
Oxalic acid is a dicarboxylic acid, meaning it contains two carboxylic acid groups (-COOH). It can act as both an acid and an oxidizing agent.

### Step 2: Analyzing the first statement
**Statement 1:** "It forms two series of salts."

- **Explanation:** Oxalic acid can form two types of salts:
1. Acid salts (e.g., sodium hydrogen oxalate, NaHC₂O₄)
2. Normal salts (e.g., sodium oxalate, Na₂C₂O₄)

- **Conclusion:** This statement is **correct**.

### Step 3: Analyzing the second statement
**Statement 2:** "Equivalent weight of H₂C₂O₄ as an acid for complete neutralization and as an oxidant are the same."

- **Explanation:** The equivalent weight is calculated as the molecular weight divided by the number of replaceable hydrogen ions (basicity) or the number of electrons transferred (n-factor). For oxalic acid:
- Molecular weight = 126 g/mol
- Basicity = 2 (since it can donate two protons)

Thus, the equivalent weight as an acid = 126 g/mol / 2 = 63 g/equiv.

As an oxidizing agent, when it reacts, it also transfers 2 electrons (n-factor = 2). Therefore, the equivalent weight remains the same.

- **Conclusion:** This statement is **correct**.

### Step 4: Analyzing the third statement
**Statement 3:** "100 ml of 0.1 molar solution of calcium hydroxide will be completely neutralized by 50 ml of 0.2 molar H₂C₂O₄."

- **Explanation:**
- For calcium hydroxide (Ca(OH)₂), the n-factor = 2 (since it can donate 2 OH⁻ ions).
- For H₂C₂O₄, the n-factor = 2 (since it can donate 2 protons).

We can calculate the gram equivalents:

For Ca(OH)₂:
\[ \text{Gram equivalents} = n \times \text{Volume (L)} \times \text{Molarity} = 2 \times 0.1 \times 0.1 = 0.02 \text{ equivalents} \]

For H₂C₂O₄:
\[ \text{Gram equivalents} = n \times \text{Volume (L)} \times \text{Molarity} = 2 \times 0.05 \times 0.2 = 0.02 \text{ equivalents} \]

Since both gram equivalents are equal, complete neutralization is possible.

- **Conclusion:** This statement is **correct**.

### Step 5: Analyzing the fourth statement
**Statement 4:** "Potassium permanganate reacts with oxalic acid."

- **Explanation:** In the reaction between potassium permanganate (KMnO₄) and oxalic acid, KMnO₄ is reduced from Mn⁺7 to Mn⁺2, which involves the transfer of 5 electrons. The n-factor for KMnO₄ is 5, while for H₂C₂O₄, it is 2. Therefore, the gram equivalents will not be equal, and complete neutralization cannot occur.

- **Conclusion:** This statement is **incorrect**.

### Final Conclusion
The correct statements about H₂C₂O₄ are:
1. It forms two series of salts.
2. The equivalent weight of H₂C₂O₄ as an acid for complete neutralization and as an oxidant are the same.
3. 100 ml of 0.1 molar solution of calcium hydroxide will be completely neutralized by 50 ml of 0.2 molar H₂C₂O₄.