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Difficulty: MediumNoble Gases: Isolation, Electronic Structure, and Uses

Helium is used in deep-sea diving gas mixtures (heliox) to prevent decompression sickness and in meteorological balloons to provide lift. Which set of properties makes helium suitable for both of these applications?

  1. Low solubility in blood under pressure, low density, and non-flammabilityAnswer
  2. B
    High solubility in blood under pressure, low boiling point, and strong reducing ability
  3. C
    High density, rapid reaction with oxygen, and high thermal conductivity
  4. D
    Ease of liquefaction at room temperature, high solubility, and low ionization energy

Answer

Low solubility in blood under pressure, low density, and non-flammability
Helium's 1s21s^2 stable electronic duplet makes it non-flammable and chemically inert. Its small molar mass (4 g/mol4\text{ g/mol}) makes it less dense than air, providing lift for weather balloons. Furthermore, its exceptionally low solubility in blood under pressure prevents decompression sickness ('the bends') in deep-sea divers.

Step-by-Step Solution

1
Analyze the requirements for deep-sea diving gas mixtures (heliox).
The gas mixed with oxygen must have low solubility in blood at high underwater pressures to prevent nitrogen narcosis and painful bubble formation upon decompression.
Helium replaces nitrogen in heliox because of its minimal blood solubility under pressure.
2
Analyze the requirements for meteorological (weather) balloons.
The gas must be less dense than air to provide upward buoyant force and non-flammable to prevent explosion hazards.
Helium has a molar mass of 4 g/mol (much lower than air's average of 29 g/mol) and a complete 1s21s^2 valence shell, making it non-flammable and safe compared to hydrogen.
3
Synthesize the properties into a single matching choice.
The combination of low blood solubility under pressure, low density, and chemical non-flammability correctly describes helium's behavior.
This set of physical and chemical properties uniquely qualifies helium for both applications.

Key Concept

Properties and Applications of Helium
Estimated Time:1m 0s
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Topics

Noble Gases: Isolation, Electronic Structure, and Uses

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