Helium mixed with oxygen is used by the sea divers in preference to nitrogen-oxygen mixture , because

Options

A. Helium is much less soluble in blood than nitrogen
B. nitrogen is much less soluble in blood than helium
C. due to high pressure nitrogen reacts with oxygen to give poisonous nitricoxide
D. nitrogen is highly soluble in water

Answer

**Step-by-Step Solution:**

1. **Understanding the Context**: Sea divers often work at great depths where the pressure is significantly higher than at sea level. This increased pressure affects the solubility of gases in the blood.

2. **Identifying the Gases**: The two gas mixtures in question are:
- Helium mixed with oxygen (He-O2)
- Nitrogen mixed with oxygen (N2-O2)

3. **Solubility in Blood**:
- Helium is known to be much less soluble in blood compared to nitrogen. This means that when divers breathe helium, less of it dissolves in their blood.
- Nitrogen, on the other hand, is more soluble in blood. When divers ascend too quickly after breathing nitrogen, the dissolved nitrogen can form bubbles in the bloodstream, leading to decompression sickness (also known as "the bends").

4. **Safety Considerations**:
- Because helium is less soluble, it reduces the risk of nitrogen narcosis and decompression sickness. This makes it a safer choice for divers who need to avoid the complications associated with nitrogen.

5. **Conclusion**: Therefore, the primary reason sea divers prefer a helium-oxygen mixture over a nitrogen-oxygen mixture is that helium is much less soluble in blood than nitrogen, which minimizes the risk of dangerous conditions associated with high-pressure diving.

**Final Answer**: Helium mixed with oxygen is used by sea divers in preference to nitrogen-oxygen mixture because helium is much less soluble in blood than nitrogen.

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