The correct answer is 5.
Thermal conductivity is a measure of a material’s ability to conduct heat. It is defined as the amount of heat that flows through a material per unit area, per unit time, and per unit temperature difference.
The thermal conductivity of hydrogen is about 5 times that of air. This means that hydrogen is a much better conductor of heat than air. This is because hydrogen molecules are very small and have a low mass. This allows them to move quickly and easily, which helps to transfer heat.
Air molecules, on the other hand, are much larger and have a higher mass. This makes it more difficult for them to move, which reduces their ability to transfer heat.
As a result, hydrogen is a much better conductor of heat than air. This is why hydrogen is often used in heat transfer applications, such as in refrigerators and air conditioners.
Here is a brief explanation of each option:
- Option A: 2. Hydrogen is about 5 times more conductive than air, not 2 times more conductive.
- Option B: 3. Hydrogen is about 5 times more conductive than air, not 3 times more conductive.
- Option C: 5. Hydrogen is about 5 times more conductive than air.
- Option D: 7. Hydrogen is about 5 times more conductive than air, not 7 times more conductive.