Question

A 60 ft3 rigid, insulated tank

(1.7 m3
) contains air at 75 psia (510.2 kPa) and 120oF (49oC). A valve
connected to the tank is opened, allowing air to escape until the pressure inside the tank drops to 30
psia (204.1 kPa). A resistor is used to heat the air inside the tank during the discharge process.
Consider ideal gas model with constant specific heats. The state of the air at the exit boundary is
defined by the average temperature between the beginning and end of the process. (A) Determine the electrical work in kJ
during the process. A: W = – 813.5 kJ.

Answer 1

The amount of work done by the system is approximately 10.0 kJ.

Step-by-step explanation:

To find the work done by the system, we can use the formula:

Work = Pressure * Change in Volume

Since the pressure is constant and given in atm, we need to convert it to Pa:

1. 1 atm = 1.01325 × 105 Pa
2. 40.0 atm = 40.0 * 1.01325 × 105 Pa

The change in volume can be calculated as the difference between the final and initial volumes:

Change in Volume = Final Volume - Initial Volume

Plugging in the values, we get:

Work = Pressure * Change in Volume = (40.0 * 1.01325 × 105 Pa) * (458 L - 177 L)

Finally, we can convert the work from Joules to kilo-joules:

Work (kJ) = Work (J) / 1000

Calculating this, the amount of work done by the system is approximately 10.0 kJ.