When `Na_(2)S_(2)O_(3)` is reacted with `I_(2)` to form `Na_(2)S_(4)O_(6)` and Nal then which statement is correct ?

Options

A. n-factor for `Na_(2)S_(2)O_(3)` is one
B. n-factor for `I_(2)` is two
C. 2 moles of `Na_(2)S_(2)O_(3)` is reacted with one mole of `I_(2)`
D. n-factor for `Na_(2)S_(4)O_(6)` is one

Answer

To solve the problem, we need to analyze the reaction between sodium thiosulfate (Na₂S₂O₃) and iodine (I₂) to form sodium tetrathionate (Na₂S₄O₆) and sodium iodide (NaI). We will evaluate each statement provided in the question.

### Step 1: Write the Balanced Chemical Equation
The reaction can be represented as:
\[ 2 \text{Na}_2\text{S}_2\text{O}_3 + \text{I}_2 \rightarrow \text{Na}_2\text{S}_4\text{O}_6 + 2 \text{NaI} \]

### Step 2: Determine the Oxidation States
1. **For Na₂S₂O₃:**
- Sodium (Na) = +1 (2 atoms contribute +2)
- Oxygen (O) = -2 (3 atoms contribute -6)
- Let the oxidation state of sulfur (S) be \( x \).
- The equation for the oxidation state becomes:
\[ 2 + x + x - 6 = 0 \]
\[ 2x - 4 = 0 \]
\[ 2x = 4 \]
\[ x = +2 \] (for each sulfur atom in Na₂S₂O₃)

2. **For Na₂S₄O₆:**
- Sodium (Na) = +1 (2 atoms contribute +2)
- Oxygen (O) = -2 (6 atoms contribute -12)
- Let the oxidation state of sulfur (S) be \( y \).
- The equation for the oxidation state becomes:
\[ 2 + 4y - 12 = 0 \]
\[ 4y - 10 = 0 \]
\[ 4y = 10 \]
\[ y = +2.5 \] (for each sulfur atom in Na₂S₄O₆)

### Step 3: Calculate the Change in Oxidation States
- For sulfur in Na₂S₂O₃: +2 to +2.5
- Change = \( 2.5 - 2 = 0.5 \)
- Since there are 2 sulfur atoms in Na₂S₂O₃, the total change is:
\[ \text{n factor} = 2 \times 0.5 = 1 \]

### Step 4: Calculate the n Factor for Iodine
- For iodine (I₂):
- Oxidation state changes from 0 (in I₂) to -1 (in NaI).
- Change = \( 0 - (-1) = 1 \)
- Since there are 2 iodine atoms, the n factor is:
\[ \text{n factor} = 1 \times 2 = 2 \]

### Step 5: Calculate the n Factor for Na₂S₄O₆
- For Na₂S₄O₆:
- Change in oxidation state for sulfur is from +2 to +2.5.
- Change = \( 2.5 - 2 = 0.5 \)
- Since there are 4 sulfur atoms, the n factor is:
\[ \text{n factor} = 4 \times 0.5 = 2 \]

### Step 6: Evaluate Each Statement
- **Statement A:** n factor of Na₂S₂O₃ is 1. **(Correct)**
- **Statement B:** n factor for iodine is 2. **(Correct)**
- **Statement C:** 2 moles of Na₂S₂O₃ react with 1 mole of iodine. **(Correct)**
- **Statement D:** n factor for Na₂S₄O₆ is 1. **(Incorrect, it is 2)**

### Conclusion
The correct statements are A, B, and C.

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