Absorbed into a solid porous material that results in an internal receptacle pressure of less than 101.3 kPa at 20°C and less than 300 kPa at 50°C describes which gas type?

• A. Gas
• B. Dissolved Gas
• C. Liquefied Gas
• D. Absorbed Gas

Answer: (D)

Absorbed gas is stored by being physically held inside the pores of a solid material. Because the gas is trapped within a porous solid rather than existing as a free gas or as a liquid, the pressure inside the receptacle stays relatively low and is governed by how much gas the material can adsorb at a given temperature. The stated pressures—less than atmospheric at 20°C and under 300 kPa at 50°C—fit this behavior, reflecting adsorption limits rather than the high pressures of compressed or liquefied gas. This description wouldn’t apply to a simple Gas (which would be a free gas phase at whatever pressure is present), a Dissolved Gas (gas dissolved in a liquid), or a Liquefied Gas (gas that exists as a liquid under pressure/low temperature).