Chapter 11 Gases Pages

The Gas Laws Robert Boyle discovered that doubling the __________ on a sample of gas at a constant temperature (because temperature can affect volume) reduces its ___________ by one half. As one variable _________ the other ________. When the volume of a container is decreased, but the same number of gas molecules is present at the same temperature, what happens to the pressure?

The Gas Laws Boyle’s law stats that the _______ of a fixed mass of gas varies inversely with the pressure at constant temperature. BOYLE’S EQUATION  P 1 V 1 = P 2 V 2 where pressure is “P” and volume is “V”. PRACTICE: A sample of oxygen gas has a volume of 150 mL when its pressure is atm. What will the volume of the gas be at a pressure of atm if the temperature remains constant? P 1 = atm V 1 = 150 mL P 2 = atm V 2 = ????

The Gas Laws Example worked on the chalk board by teacher. Take these notes as they will be scored on the next notebook check! For reflection practice, work the practice problem using Boyle’s law: a balloon filled with helium 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?

The Gas Laws __________________ states that the volume of a fixed mass of a gas at constant pressure varies directly with the temperature. While Boyle’s law deals with pressure and volume, Charles’ law deals with temperature and volume. To calculate temperature using Charles’ law, one must first convert temperature to Kelvin. If given Celsius temperature, how do we convert a temperature from Celsius to Kelvin? When given a temperature in Celsius, to convert to Kelvin, add 273 to the amount given. The formula for Charles’ law is V 1 = V 2 T 1 T 2 T 1 T 2 PRACTICE: A sample of neon gas occupies a volume of 752 mL at 25 degrees C. What volume will the gas occupy at 50 degrees C if the pressure remains constant?

The Gas Laws

The __________________ expresses the relationship between pressure, volume and temperature of a fixed amount of gas. The formula for the combined gas law is P 1 V 1 = P 2 V 2 T 1 T 2 T 1 T 2 Remember, for gas calculations, you must convert temperatures given in degrees Celsius to Kelvin! To do this, always add 273 to the amount given for degrees Celsius. A helium-filled balloon has a volume of 50 L at 25 degres C and 1.08 atm. What volume will it have at atm and 10 degrees C? Calculation will be worked on the chalk board by teacher.

The Ideal Gas Law The ________________________ is the mathematical relationship among pressure, volume, temperature and the number of moles of a gas. The Ideal gas law equation is PV = nRT Where P is pressure V is volume n is the number of moles R is a constant T is the temperature These types of calculations will require extensive algebraic manipulation!

The Ideal Gas Law The gas constant R is L x atm mol x K mol x K PRACTICE: What is the pressure in atmospheres exerted by a 0.5 mol sample of nitrogen gas in a 10 L container at 298K? PV = nRT P= ? V= 10L n= 0.5 mol R= L x atm mol x K mol x K T= 298K