International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

Carbon dioxide is used in fire extinguishers primarily due to its ability to displace oxygen, which is essential for combustion. When CO2 is released from the extinguisher, it envelops the fire and reduces the concentration of oxygen in the vicinity. This helps to smother the flames and effectively suppress the fire. Additionally, CO2 is non-flammable and does not conduct electricity, making it safe for use in a variety of fire situations, including electrical fires.

In contrast, while options like pharmaceuticals, heating systems, and lubricants are important sectors in chemistry, they do not typically involve carbon dioxide in the same primary capacity as fire extinguishers. Pharmaceuticals may incorporate CO2 in certain processes, but it is not its main application. Similar reasoning applies to heating systems, where other gases or systems are more commonly utilized, and CO2 is not used as a heating agent. For lubricants, carbon dioxide does not play a direct role in their formulation or function compared to other substances better suited for that application.