Which gas is colorless, odorless, and lighter than air, with an explosive range of 5%-15%?

Methane is the correct choice because it is a colorless and odorless gas that is lighter than air, typically having a molecular weight of about 16 g/mol, which allows it to rise in the atmosphere. One of the crucial safety aspects of methane is its explosive range, which falls between 5% and 15% in the air. This means that if the concentration of methane in the air is within this range, there is a risk of combustion if an ignition source is present.

Understanding these characteristics is vital for working safely in environments where methane may be present, particularly in confined spaces. Monitoring for methane and ensuring proper ventilation can reduce the risk of explosive atmospheres, thereby protecting workers from potential hazards.

In contrast, carbon dioxide does not have an explosive range and is denser than air; nitrogen is also colorless and odorless, but it is not flammable; hydrogen peroxide is a liquid at room temperature and is not classified as a gas.