A system of ideal gas has an initial pressure of 111 kPa and occupies a volume of 5.00 liters. Doubling the system’s absolute temperature by means of a constant-pressure process would require an amount of work W. Instead, you decide to double the absolute temperature by carrying out two processes in sequence, a constant-pressure process followed by a constant-volume process. In this case, the total work done in the two-process sequence is W/2. Calculate the final pressure of the system.

Respuesta :

Answer:

The final pressure is 148 kPa

Solution:

As per the question:

Initial Pressure of the gas, P = 111 kPa

Initial Volume, V = 5.00 l

Now,

In order to calculate the final pressure of the system:

At constant pressure, the work done is 'W'

If the absolute initial temperature be T

When the absolute temperature is doubled, T' =2T

Total work done in the processes, W = [tex]\frac{W}{2}[/tex]

Now,

From the ideal gas eqn:

PV = nRT

PV ∝ T                      (1)

In constant pressure process, work done is given by:

W = [tex]P\Delta V[/tex]                   (2)

Thus from eqn (1) and (2):

[tex]\frac{V}{V'}= \frac{T}{T'}[/tex]

In the first process, temperature is doubled:

[tex]\frac{V}{V'}= \frac{T}{2T}[/tex]

V = 2V'

Thus

[tex]V' = \frac{V}{2}[/tex]

In the process, the change in volume is [tex]\frac{V}{2}[/tex] given by:

[tex]V_{t} = V + \frac{V}{2} = \frac{3V}{2}[/tex]

Now,

[tex]\frac{PV}{P'V'} = \frac{T}{T'}[/tex]

[tex]\frac{PV}{P'\frac{3V}{2}} = \frac{T}{2T}[/tex]

[tex]\frac{P}{P'\frac{3}{2}} = \frac{1}{2}[/tex]

[tex]P' = \frac{4}{3}P[/tex]

[tex]P' = \frac{4}{3}\times 111 = 148\ kPa[/tex]