SCIENCE: Physics - Charles' law, Gay-Lussac's law, gas law

Charles' law

Also known as the law of volumes, Gay-Lussac's law

V T curve is a straight line

At constant pressure, the volume of a fixed mass of gas varies directly with the absolute temperature

At constant volume, the gas pressure varies directly with the absolute temperature



V1/T1 = V2/T2  ---> if p = constant


p1/T1 = p2/T2  ---> if v = constant


where:

p1 = absolute pressure at point1

p2 = absolute pressure at point2

V1 = gas volume at point1

V2 = gas volume at point2

T1 = absolute temperature at point1

T2 = absolute temperature at point2



1. Problem:

Air occupies a volume of 70 L at 300 K. If the pressure remains constant, find the temperature of the air when the volume increased to 140 L.


find:

T2 = temperature of the air at V2 = 140 L


given:

p = c

V1 = 70 L

T1 = 300 K

V2 = 140 L


solution:

V1/T1 = V2/T2

70/300 = 140/T2

T2 = 300 * 140/70

T2 = 600 K

thus, direct proportion between volume and absolute temperature. The initial volume of 70 L was doubled to 140 L and therefore 300 K is also doubled giving 600 K.




2. Problem:

In a constant volume process, oxygen has a temperature of 80 C under a pressure of 4 atm. If the pressure is halved, calculate the final temperature.


find:

T2 = final temperature


given:

v = c

T1 = 80 + 273

T1 = 353 K

p1 = 4 atm

p2 = 2 atm


solution:

p1/T1 = p2/T2

4/353 = 2/T2

T2 = 353 * 2/4

T2 = 176.5 K ---> T2 also halved when p2 is halved