What is the specific gravity of Hydrogen compared to other gases?

The correct answer highlights that hydrogen is recognized as the lightest of all gases, which is reflected in its specific gravity of approximately 0.07 when compared to air. Specific gravity is a measure of the density of a substance relative to another substance, typically air in the case of gases. Since hydrogen is much less dense than air, its specific gravity is significantly lower than 1. This means that hydrogen will rise in air, which is a crucial consideration in mining and industrial scenarios where gas behavior can impact safety and operations.

The choice referencing hydrogen as the heaviest of all gases is incorrect because hydrogen, with its very low molecular weight, is far lighter than many other gases, such as carbon dioxide and even air itself. Additionally, stating that hydrogen has the same specific gravity as oxygen is misleading, as oxygen has a specific gravity of approximately 1.1, clearly indicating it is denser than hydrogen. The option mentioning a specific gravity of 0.91 does not align with hydrogen's known properties; thus, it misrepresents hydrogen's characteristic as being the lightest gas.