The Gas Laws

11.2

Boyle’s Law•Boyle’s Law – the volume of a fixed mass of gas varies inversely with the pressure at constant temp.

•PV = k•You can relate 2 different gases w/ k

•P1V1 = P2V2

Practice

•A sample of O2 gas has a vol of 150.00 mL when it’s P is 0.947 atm. What will the vol of the gas be at a P of 0.987 atm if the T remains constant?

•Make sure both P and V units are the same!

Practice

•A balloon filled with He gas has a vol of 500 mL at a P of 1 atm. The balloon is released and reaches an altitude of 6.5 km, where the P is 0.5 atm. If the T has remained the same, what volume does the gas occupy at this height?

Temperature

•Absolute zero – the T of -273.15 °C is given a value of 0 in the Kelvin scale.

•K = 273.15 + °C •Charles’ Law = the vol of a fixed mass of gas at constant P varies directly with the Kelvin Temp

Charles’ Law

•V = kT•V = k T•V1 = V2

T1 = T2

Practice•A sample of neon gas occupies a volume of 752 mL at 25°C. What V will the gas occupy at 50°C if the P is constant?

•A sample of N2 gas is contained in a piston w/a freely moving cylinder. At 0°C, the V of the gas is 375 mL. To what T must the gas be heated to occupy a V of 500.0 mL?

Gay-Lussac’s Law•The P of a fixed mass of a gas at constant V varies directly with the Kelvin T

•P = kT P = kT

Set K equal to get…P1 = P2

T1 = T2

Practice

•The gas in a container is at a P of 3.00 atm at 25°C. Directions on the container warn the user not to keep it in a place where the T exceeds 52°C. What would the P be at 52°C?

Practice•At 120.0 °C, the pressure of a sample of nitrogen is 1.07 atm. What will the pressure be at 205 °C, assuming constant volume.

•A sample of He gas has a P of 1.20 atm at 22 °C. At what Celsius Temp will the He reach a P of 2.00 atm, assuming constant V.

The Combined Gas Law

•Combines Charles’, Boyle’s, and G-L

•CGL – expresses the relationship b/t P, V, and T of a fixed amt of gas

PV = k P1V1 = P2V2

T T1 T2

•T must be in Kelvin!!!!!

Practice•A helium Balloon has a volume of 50.0 L at 25°C and 1.08 atm. What V will it have at 0.855 atm & 10.0°C?

•A 700.0 mL gas sample at STP is compressed to a V of 200.0 mL, and the T is increased to 30.0 °C. What is the new P of the gas in Pa?

•Complete S.R. on page 375 # 1-5