Question

When ${CO}_2$ under high pressure is released from a fire extinguisher, particles of solid $C$ despite the low sublimation temperature $(-{77}^{0}C)$ of ${CO}_2$ at 1.0 atm. It is:

• A. the gas does work pushing back the atmosphere using KE of molecules and thus temperature
• B. volume of the gas is decreased rapidly hence, temperature is lowered
• C. both $A$ and $B$
• D. none of the above

Answer 1

The correct option is A the gas does work pushing back the atmosphere using KE of molecules and thus temperature

• Carbon dioxide ($C{O}_2$) extinguishers contain a mixture of liquid and gaseous carbon dioxide (a nonflammable gas).
• $C{O}_2$ is normally a gas at room temperature and pressure. It has to be stored under high pressure to make it a liquid. When you release the pressure, the gas expands enormously and makes a huge white jet.
• $C{O}_2$ attacks the fire triangle in two ways: it smothers the oxygen and, when it turns from a liquid back to a gas, it "sucks" in a massive amount of heat from its surroundings (the latent heat of vaporization), which cools whatever you spray it on by removing heat.
• $C{O}_2$ is designed for Class B and C (flammable liquid and electrical) fires only.
• When $C{O}_2$ under high pressure is released from a fire extinguisher, particles of solid C despite the low sublimation temperature it is the gas does work pushing back the atmosphere using KE of molecules and thus temperature.
  
• Hence option A is correct answer.