Which gas has a heating value close to 2500 btu/cubic foot?

The heating value of a gas represents the amount of energy released when a given volume of that gas is combusted. Propane gas has a heating value close to 2500 BTU per cubic foot, making it suitable for applications where a higher energy input per volume is required.

Propane, which is derived from natural gas processing and crude oil refining, is known for its efficient combustion and higher energy content compared to many other gases, which is why it is often used in heating, cooking, and certain industrial applications.

In contrast, other gases listed, like nitrogen, have negligible heating values and are not fuel gases. Natural gas and methane, while closely related and primarily composed of methane, typically have higher heating values (around 1000-1100 BTU per cubic foot for natural gas) rather than the 2500 BTU mark presented in the question. Thus, propane stands out as the correct choice based on its heating characteristics.