Estimation of reducing substances by the use of standard `I_(2)`,
`I_(2)+2S_(2)O_(3)^(2-)rarr S_(4)O_(6)^(2-)+2I^(Theta)` is called

Options

A. Ioimetry
B. Iodometry
C. Oxidising
D. Reducing

Answer

To solve the question regarding the estimation of reducing substances using standard iodine (I₂), we will analyze the provided reaction and the definitions of related terms.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
The reaction given is:
\[ I_2 + 2 S_2O_3^{2-} \rightarrow S_4O_6^{2-} + 2 I^{-} \]
In this reaction, iodine (I₂) is reacting with thiosulfate ions (S₂O₃²⁻) to produce tetrathionate ions (S₄O₆²⁻) and iodide ions (I⁻).

2. **Identifying the Process**:
The process involves the use of iodine (I₂) to estimate the amount of reducing substances present in a solution. The iodine acts as an oxidizing agent and gets reduced to iodide ions (I⁻) in the process.

3. **Differentiating Between Terms**:
- **Iodimetry**: This term refers to the estimation of reducing agents by using iodine (I₂) as a titrant. It involves the direct titration of reducing substances with standard iodine.
- **Iodometry**: This term refers to the estimation of oxidizing agents by adding iodide ions to form iodine, which is then titrated. Here, iodine acts as an oxidizing agent.

4. **Conclusion**:
Since the question specifically asks for the estimation of reducing substances using standard iodine, the correct term for this process is **Iodimetry**.

### Final Answer:
The estimation of reducing substances by the use of standard I₂ is called **Iodimetry**.

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