Gay-Lussac's Law

This relationship between pressure and temperature was studied by Joseph Louis Gay-Lussac, a French Chemist. This law states that pressure is directly proportional to the absolute temperature when volume and amount of gas is held constant.
This law is mathematically expressed as:

P1 = P2

T1 T2

Sample Problem:

A sample of gas at 3000mm Hg inside a steel tank is cooled from500ºC to 0ºC. What is the final pressure of the gas inside the steel taank?

Given:

P1 = 3000 mm Hg

T1 = 500ºC + 273 = 773K

P2 = ?

T2 = 0ºC + 273 = 273K

Solution:

P1 = P2
T1 T2

(3000 mm Hg) = P2

(773K) (273K)

P2 = (3000 mm Hg)(273K)

773K

P2 = 1,059.51 mm Hg

Exercises:

1. A gas sample has a pressure of 950 torr at 120ºC. What is the final pressure of the gas after the temperature is dropped to 10ºC?
2. Pressure of a gas in a 10.0L steel cylinder is 890torr at 56ºC. To what temperature should the gas be cooled in order to reduce the pressure to 760 torr?