Gay-Lussac’s Law

As temperature increases, in a rigid container with constant volume, the average speed of the gas molecules increases, creating more collisions with the walls of the container, and as a result the gas pressure increases.

Gay-Lussac’s Law

Pressure of a fixed amount of gas, at constant volume, is directly proportional to its Kelvin temperature

Pi Pf

Ti Tf

=

Graphically

A cylinder of chlorine gas is stored in a concrete-lined room for safety. The cylinder is designed to

withstand 50 atm of pressure. The pressure gauge reads 35.0 atm at 23.2°C. An accidental

fire in the room next door causes the temperature in the storage room to increase to 87.5 °C. What will the pressure gauge read at

this temperature?

1. What are you trying to determine?

What will the pressure gauge read at this temperature? Pf

Step 2: Identify what is given:Pi = 35.0 atm

Ti = 23.2 °C

Tf = 87.5 °C

Step 3: Convert temperatures from °C to K

Ti = 23.2 °C Tf = 87.5 °C

= 23.2 °C + 273 = 87.5 °C + 273

= 296 K = 360 K

Step 4: Use equation to determine final volume:

Pi Pf

Ti Tf

35.0 atm Pf

296 K 360 K

Pf = 42.7 atm

=

=