A colourless, nonirritant, highly toxic gas that impairs respiration is

Options

A. `SO_(2)`
B. `NO_(2)`
C. `CO_(2)`
D. CO

Answer

**Step-by-Step Solution:**

1. **Identify the Characteristics of the Gas**: The question describes a gas that is colorless, non-irritant, and highly toxic, which impairs respiration.

2. **Consider Common Gases**: Think about gases that fit these characteristics. Common gases that are colorless and can be toxic include carbon monoxide (CO) and carbon dioxide (CO2).

3. **Analyze Carbon Monoxide (CO)**:
- Carbon monoxide is colorless and odorless.
- It is non-irritant, meaning it does not cause immediate irritation upon inhalation.
- It is highly toxic and can impair respiration by binding to hemoglobin in the blood, forming carboxyhemoglobin, which reduces the blood's ability to carry oxygen.

4. **Analyze Carbon Dioxide (CO2)**:
- Carbon dioxide is also colorless but is not classified as highly toxic in normal concentrations.
- It can cause respiratory issues in high concentrations, but it is not as acutely toxic as carbon monoxide.

5. **Conclusion**: Based on the analysis, the gas that fits all the criteria of being colorless, non-irritant, and highly toxic while impairing respiration is carbon monoxide (CO).

**Final Answer**: The gas is carbon monoxide (CO).

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