Answer :
Final answer:
Carbon dioxide fire extinguishers are effective against Class B and C fires by displacing oxygen, hence smothering the fire. The presence of liquid CO2 in the extinguisher depends on the temperature in relation to the critical temperature of CO2, which is 31 °C. Above this temperature, CO2 will not be liquid despite the pressure in the extinguisher.
Explanation:
Carbon dioxide fire extinguishers are effective in fighting Class B and Class C fires. These extinguishers work by displacing oxygen in the air around the fire, effectively smothering the flames and preventing the chemical reaction that is combustion. Carbon dioxide is a non-conductive gas, which is why it works well on electrical fires, classifying it as useful in extinguishing Class C fires.
The state of carbon dioxide in a fire extinguisher can be understood by considering its critical temperature. This is the temperature above which a gas cannot be liquefied, regardless of pressure. For carbon dioxide, the critical temperature is 31 °C (304 K). On a cool day, with temperatures below 31 °C, it is possible to have liquid CO2 inside the cylinder. However, on a hot summer day with temperatures above 31 °C, the CO2 will only exist as a gas inside the extinguisher, as it cannot be liquefied above its critical temperature.
