Why is helium preferred over hydrogen for use in airships ?

Options

A. Helium has a low density
B. Helium has a high density
C. Helium is chemically less reactive
D. Helium is chemically more reactive.

Explanation

### Step-by-Step Solution:

1. **Understanding the Properties of Gases**:
- Hydrogen and helium are both lighter than air, which allows them to provide lift in airships. However, their chemical properties differ significantly.

2. **Flammability of Hydrogen**:
- Hydrogen is a highly flammable gas. It can easily ignite and cause explosions when mixed with air and exposed to a spark or flame. This poses a significant safety risk when used in airships.

3. **Non-flammability of Helium**:
- Helium, on the other hand, is a noble gas and is non-flammable. It does not react with other substances and will not catch fire, making it a much safer option for use in airships.

4. **Chemical Reactivity**:
- Helium is chemically inert, meaning it does not readily participate in chemical reactions. This stability adds to its safety profile, especially in applications where flammability is a concern.

5. **Conclusion**:
- Due to the flammability of hydrogen and the non-flammability of helium, helium is preferred over hydrogen for use in airships. This choice enhances safety and reduces the risk of fire-related accidents.

### Final Answer:
Helium is preferred over hydrogen for use in airships because helium is non-flammable and chemically inert, while hydrogen is highly flammable and poses a significant safety risk.

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