Which of the following halogen oxide is used for estimation of carbon monoxide in automobile exhaust gases?

Options

A. `Cl_(2)O_(7)`
B. `I_(2)O_(5)`
C. `ClO_(2)`
D. `BrO_(3)`

Explanation

To solve the question regarding which halogen oxide is used for the estimation of carbon monoxide in automobile exhaust gases, we can follow these steps:

### Step 1: Identify the Halogen Oxides
The options given are:
1. Cl2O7
2. I2O5
3. ClO2
4. BrO3

### Step 2: Understand the Reaction for Estimation of Carbon Monoxide
The estimation of carbon monoxide (CO) can be carried out using a specific halogen oxide. In this case, it is known that iodine pentoxide (I2O5) is used for this purpose.

### Step 3: Write the Reaction Involving I2O5
The reaction for the estimation of carbon monoxide using iodine pentoxide can be represented as follows:
\[ 5 \text{CO} + \text{I}_2\text{O}_5 \rightarrow 5 \text{CO}_2 + \text{I}_2 \]

### Step 4: Analyze the Products
In this reaction, carbon monoxide is oxidized to carbon dioxide, and iodine (I2) is liberated. The liberated iodine is violet in color and can be further used in titration.

### Step 5: Titration of Iodine
The liberated iodine can be titrated against a thiosulfate solution (hypo solution) as follows:
\[ \text{I}_2 + 2 \text{Na}_2\text{S}_2\text{O}_3 \rightarrow 2 \text{NaI} + \text{Na}_2\text{S}_4\text{O}_6 \]

### Step 6: Calculate Moles of Carbon Monoxide
From the stoichiometry of the reaction, we know that:
- 5 moles of CO correspond to 1 mole of I2.
- By determining the moles of I2 from the titration, we can calculate the moles of CO present in the sample.

### Conclusion
Based on the analysis, the halogen oxide used for the estimation of carbon monoxide in automobile exhaust gases is **I2O5** (option 2).

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