Final answer:
A fire extinguisher's charge level is typically checked using a pressure gauge. For a CO₂ extinguisher exposed to a temperature increase, the final internal pressure can be calculated using the combined gas law, relating the initial and final temperatures and pressures.
Step-by-step explanation:
To check if a fire extinguisher is fully charged, you typically look at the pressure gauge that most extinguishers are equipped with. This gauge often has a green zone indicating that the pressure is within the safe operating range.
If you want to calculate the internal pressure after a change in temperature, as in the case of a CO₂ fire extinguisher left in a hot car, you can use the combined gas law. This law relates temperature, pressure, and volume when the amount of gas is constant. For the scenario provided, where a fire extinguisher is filled with CO₂ at 20.0 atm and 21°C, and later the temperature inside the car rises to 71.1°C, we can use the formula:
P1/T1 = P2/T2
Where P1 and T1 are the initial pressure and temperature (in Kelvin), and P2 and T2 are the final pressure and temperature. Calculating this, we can find the internal pressure of the CO₂ fire extinguisher under those temperature conditions.