Question

It is required to reduce the volume of a gas by 20% by compressing it at a constant pressure. To do so the gas has to be cooled. If the gas attains a final temperature of 157 degrees C, find the initial temperature of the gas.

Answer 1

P1V1/T1 = P2V2/T2 , but omit P because it is constant.

For volume you can use a ratio: 100 to 80 or 1 to 0.8 whichever you find convenient. I will use 1 to 0.8 Now substitute into the equation , temperature in K : 157°C = 430K

V1/T1 = V2/T2
1/T1 = 0.8/430
T1 = 430/0.8
T1 = 537.5 K
Original temperature = 537.5- 273 = 265°C