Which one is incorrect statement ?

Options

A. He is used in gas cooled nuclear reactors
B. He is used as a cryogenic agent for carrying out experiments at low temperature
C. He is used to produce and sustain powerful super conducting magnet
D. He is used to fill gas bolloons instead of `H_(2)` because it is lighter than `H_(2)` and non-inflammable

Answer

To determine which statement about helium is incorrect, we will analyze each of the provided statements one by one.

### Step-by-Step Solution:

1. **Statement 1: Helium is used in gas-cooled nuclear reactors.**
- Helium is indeed used as a coolant in gas-cooled nuclear reactors due to its inert nature and high thermal conductivity.
- **Conclusion:** This statement is **true**.

2. **Statement 2: Helium is used as a cryogenic agent for carrying out experiments at low temperature.**
- Helium is widely used in cryogenics because it remains in a liquid state at extremely low temperatures, making it ideal for cooling applications in scientific experiments.
- **Conclusion:** This statement is **true**.

3. **Statement 3: Helium is used to produce and sustain powerful superconducting magnets.**
- Helium is essential in the cooling of superconducting magnets, as it helps maintain the low temperatures required for superconductivity to occur.
- **Conclusion:** This statement is **true**.

4. **Statement 4: Helium is used to fill balloons instead of hydrogen because it is lighter than hydrogen and non-inflammable.**
- This statement contains an error. While helium is indeed non-inflammable and is used to fill balloons, it is **not lighter than hydrogen**. In fact, hydrogen is lighter than helium. Helium is used in balloons primarily because it is non-flammable, making it safer than hydrogen.
- **Conclusion:** This statement is **incorrect**.

### Final Answer:
The incorrect statement is: "Helium is used to fill balloons instead of hydrogen because it is lighter than hydrogen and non-inflammable."

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