He is added to the oxygen supply used by sea divers because

Options

A. it is less soluble in blood than `N_(2)` a high pressure
B. it is lighter than `N_(2)`
C. it is readly miscible with `O_(2)`
D. it is less poisonous than `N_(2)`

Explanation

To answer the question of why helium is added to the oxygen supply used by sea divers, we can follow these steps:

### Step 1: Understand the context of diving
Sea divers often breathe a mixture of gases while underwater to ensure they can safely and effectively breathe at various depths. The pressure increases as divers go deeper, which affects how gases behave in the body.

**Hint:** Consider how pressure changes underwater and how it affects gas solubility.

### Step 2: Identify the gases used in diving
One common mixture used by divers is Trimix, which consists of helium, nitrogen, and oxygen. Each gas has specific properties that make it suitable for diving.

**Hint:** Think about the properties of helium, nitrogen, and oxygen, especially in relation to pressure.

### Step 3: Recognize the effects of nitrogen at high pressure
At greater depths, the increased pressure causes nitrogen to become more soluble in the blood. This can lead to nitrogen narcosis, a condition that can impair a diver's cognitive and motor functions.

**Hint:** Reflect on the implications of nitrogen solubility in the body under high pressure.

### Step 4: Understand the role of helium
Helium is less soluble in blood compared to nitrogen. By adding helium to the breathing gas mixture, divers can reduce the amount of nitrogen they breathe, thereby minimizing the risk of nitrogen narcosis and making breathing easier at depth.

**Hint:** Consider why a gas with lower solubility would be beneficial in a diving scenario.

### Step 5: Conclude the answer
Therefore, the reason helium is added to the oxygen supply used by sea divers is that helium is less soluble than nitrogen at high pressure, which helps to reduce the narcotic effects of nitrogen and enhances safety during deep dives.

**Final Answer:** Helium is added to the oxygen supply used by sea divers because it is less soluble than nitrogen at high pressure.