Question

Air(ideal gas) at 292.15k is expended by a piston from 600cm^3 to 900cm^3 at a temperature of 550k at 900kpa pressure. find the pressure before expansion.

Answer 1

The pressure before expansion is 717.1 kPa.

Step-by-step explanation:

We need to use the Ideal Gas equation to find the initial pressure:

`PV = nRT`

Where:

P: is the pressure

V: is the volume

n: is the number of moles

R: is the gas constant

T: is the temperature

Since the number of moles does not change after the expansion, we need the following number of moles:

`n = (P_(f)V_(f))/(RT_(f))` (1)

Where "f" is for final

Before the expansion, the pressure is:

`P_(i) = (nRT_(i))/(V_(i))` (2)

By entering equation (1) into (2) we have:

`P_(i) = ((P_(f)V_(f))/(RT_(f)))((RT_(i))/(V_(i)))`

`P_(i) = (P_(f)V_(f)T_(i))/(T_(f)V_(i)) = (900 kPa*900 cm^(3)*292.15 K)/(550 K*600 cm^(3)) = 717.1 kPa`

Therefore, the pressure before expansion is 717.1 kPa.

I hope it helps you!