The Gas LawsBoyles Law 11.2

Boyles Law Pressure

Volume relationship The volume of a fixed mass of gas varies inversely with the pressure at constant temperature.

Boyles law

If we reduce the volume of the container by half, but still have the same number of molecules, then the number of molecules per unit volume doubles. If we have more molecules per unit volume then we will have more collisions within a given area of the walls, which will cause the pressure to increase.

Boyles Law

Boyles Law Mathematically

expressed as

V = k (1/P) or PV = k

Can

be used to compare changing conditions of a gas at constant temperature.P1V1 = P2V2

Example problemA sample of oxygen gas has a volume of 150. mL when its pressure is 0.947 atm. What will the volume be at a pressure of 0.987 atm if the temperature remains constant? Rearrange the Equation to solve for V2 V2 = P1V1 P2

Answer = 144 mL O2

Example problem 2A balloon filled with helium gas has a volume of 500 mL at a pressure of 1 atm. The balloon is released and reaches an altitude of 6.5 km, where the pressure is 0.5 atm. If the temperature has remained the same, what volume does the gas occupy at this height?

1000 mL He

Example problem 3The piston of an internal combustion engine compresses 450. mL of gas. The final pressure is 15 times greater than the initial pressure. What is the final volume of the gas, assuming constant temperature?

30.0 mL