As an expert in the field of chemical physics, I can provide you with a detailed explanation regarding the density of hydrogen gas compared to air. Hydrogen gas is indeed less dense than air. The density of a gas is determined by its molar mass and the conditions under which it is measured, such as temperature and pressure. Under standard temperature and pressure (STP), the density of hydrogen is approximately 0.08988 g/L, while the density of air is about 1.225 g/L. This significant difference in density is what makes hydrogen an ideal candidate for applications where lift is required, such as in lighter-than-air ships or balloons.

The principle behind the buoyancy of these vessels is based on the Archimedes' principle, which states that an object submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced by the object. Since hydrogen is much less dense than air, a volume of hydrogen will displace a weight of air greater than its own weight, resulting in a net upward force, or lift.

Historically, hydrogen was used in lighter-than-air ships, such as the Hindenburg, due to its low density. However, the use of hydrogen came with significant risks, as it is highly flammable and can form explosive mixtures with air. This was tragically demonstrated by the Hindenburg disaster in 1937.

In modern times, helium has largely replaced hydrogen for lighter-than-air applications due to its non-flammability and similar lifting properties. Helium has a slightly higher density than hydrogen, approximately 0.1786 g/L at STP, but it is still less dense than air and does not pose the same explosion risks.

The reference to helium having a mass of 4 grams per 22.4 liters is correct and aligns with the molar volume of an ideal gas at STP, which is 22.4 liters. This volume contains one mole of any ideal gas, and for helium, with a molar mass of approximately 4 grams per mole, this results in the density mentioned.

In summary, hydrogen is much less dense than air, which is why it was historically used in lighter-than-air ships. However, due to safety concerns, helium is now preferred for these applications despite being twice as dense as hydrogen but still less dense than atmospheric air and not explosive.

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making it much less dense than air. This is what made Hydrogen the choice of gas for the lighter than air ships. ... Now lighter than air ships use Helium with a mass of 4 grams./ 22.4 liters of volume. Twice as dense Hydrogen but still less dense than the atmospheric air and not explosive.Sep 29, 2016read more >>