Question

Explain how $C{O_2}$ is able to control fire.

Answer 1

Hint: We need to know some properties of carbon-dioxide and how it is used to control fire. Carbon-dioxide is a molecule consisting of a carbon atom bonded to two oxygen atoms covalently. It is found naturally in the earth’s atmosphere. It acts as a greenhouse gas, and produced by the air we exhale and through other human beings such as burning of fossil fuels. It is a non-flammable gas and can be used to control fire.

Complete answer:
The most important supporter of combustion is oxygen. Normal air consists of about \[21\% \] of oxygen and the requirement of oxygen for combustion is about $16\% $ . It helps in combustion by supporting the processes that happen during the burning of fire. Oxygen itself is not flammable but supports the process.
Carbon-dioxide being a non-combustible gas also does not support combustion. It is able to control fire in the following ways:
Carbon dioxide is heavier than oxygen due to the presence of a carbon and hence can suppress the oxygen which acts as a combustion supporter.
Carbon dioxide being heavier than oxygen acts like a blanket on top of the fire thereby cutting off the contact between the oxygen and the fire.
Carbon dioxide has the capacity to expand enormously in volume and also bring a cooling effect. Hence when allowed to spread over burning fire, it expands and brings down the temperature of the fire.

Note:
It must be noted that Carbon dioxide used to control fire is available commercially in the form of fire extinguishers. These are cylinders where carbon dioxide is stored under high pressure. Due to the high pressure, the carbon dioxide liquifies and hence present in liquid form in fire extinguisher cylinders. They are handy and thus can be used in emergency situations. They are often kept in kitchens, garages and fuel pumps where there is a higher risk of combustion.