Which one of the following statements regarding helium is incorrect?

Options

A. It is used to produce and sustain powerful superconducting magnets
B. It is used to fill gas balloons instead of hydrogen because it is lighter and non - inflammable
C. It is used as a cryogenic agent for carrying out experiments at low temperatures
D. It is used in gas - cooled nuclear reactors.

Answer

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

### Step-by-Step Solution:

1. **Statement Analysis**:
- **Statement 1**: "It is used to produce and sustain powerful superconducting magnets."
- **Analysis**: This statement is correct. Liquid helium, which has a boiling point of 4.2 K, is used to cool superconducting magnets in applications like MRI machines and NMR spectrometers.

2. **Statement 2**: "It is used as the cryogenic agent for carrying out experiments at low temperatures."
- **Analysis**: This statement is also correct. Helium is indeed used as a cryogenic agent due to its low boiling point, allowing for experiments at very low temperatures.

3. **Statement 3**: "It is used in filling balloons for meteorological observations because it is lighter and non-inflammable."
- **Analysis**: This statement is correct as well. Helium is lighter than air and non-flammable, making it suitable for filling balloons used in meteorological observations.

4. **Statement 4**: "It is used as the diluent for oxygen in modern diving apparatus because of its high solubility."
- **Analysis**: This statement is incorrect. Helium is used in diving apparatus because of its **low solubility** in blood, not high solubility. The low solubility helps prevent conditions like decompression sickness (the bends) that can occur with nitrogen.

### Conclusion:
The incorrect statement regarding helium is **Statement 4**. It should state "because of its low solubility" instead of "because of its high solubility."