G AS L AWS Chapter 13 C REATE A S MALL G RAPH FOR THE FOLLOWING D ATA POINTS Pressure (mmHg)Volume (L)Temperature (K) B OYLE S L AW Pressure and Volume Constant Temperature and # of moles P1V1P1V1 P2V2P2V2 Inversely proportional If we know the volume of a gas at a given pressure, we can predict the new volume if pressure is changed and temperature/amount of gas remains the same C REATE A S MALL G RAPH FOR THE FOLLOWING D ATA POINTS Pressure (atm)Volume (L)Temperature (K) C HARLES L AW Volume and Temperature Constant Pressure and # of moles Directly proportional (linear) W HY K ELVIN ? Soccer ball example: The volume of a soccer ball is 2.89L when it is indoors at room temperature, 25.0C What is the volume of the ball when it is taken outdoors, where it is -4.50C (all other factors remain constant)? The solid lines below are actual data points for different gases If gases cool enough, they eventually liquefy, so we cant experimentally determine points below a certain temperature But, we can extrapolate this data When we do that, strangely enough, when every gas hits 0L for volume, its temperature ends up at -273C Absolute zero- lowest possible temperature that matter can be cooled to C HARLES L AW #30, pg. 439 Suppose a 375 mL sample of neon gas at 78 degrees Celsius is cooled to 22 degrees Celsius at constant pressure. What will be the new volume of the neon sample? ( get in the habit of converting Celsius to Kelvin) C = Kelvin For example: If it is -3C, this is equal to = 270K C = Kelvin For example: If it is -3C, this is equal to = 270K G AY -L USAAC S L AW Volume is held constant P 1 = P 2 T1T1 T2T2 A VOGADRO S L AW ( SAME DUDE ) Volume and Number of Moles Constant Pressure Constant Temperature Predict the trend here and draw a sketch of a graph for Avogadros Law C OMBINED GAS LAW Used if # of moles (n) remains constant but P, V, and/or T are changing MUST USE KELVIN!! If anything remains constant, it can be removed I DEAL G AS L AW The Ideal Gas Law follow the Kinetic Molecular Theory. The KMT is based on four factors: PV = nRT P- pressure in atmospheres (atm) V- volume in liters (L) n- number of moles (mol) R- universal gas constant, Latm/Kmol T- temperature in Kelvin (K) Also can use the Combined Gas Law P 1 V 1 = P 2 V 2 T 1 T 2 U SING THE I DEAL G AS L AW UNDER C HANGING C ONDITIONS Suppose we have a mol sample of ammonia gas at 25C with a volume of 3.50 L at a pressure of 1.68 atm. The gas is compressed to a volume of 1.35 L at 25C. Use the ideal gas law to determine the final pressure. I DEAL G AS LAW UNDER CHANGING CONDITIONS A sample of diborane gas (B2H6), has a pressure of atm at a temperature of -15C and a volume of 3.48L. If conditions are changed so that the temperature is 36C and the pressure is atm, what will be the new volume of the sample? I DEAL G AS LAW UNDER CHANGING CONDITIONS A sample of diborane gas (B2H6), has a pressure of atm at a temperature of -15C and a volume of 3.48L. If conditions are changed so that the temperature and volume stay constant, but the pressure changes to atm, calculate in grams how much substance was added to the system? P 1 V 1 = nRT 1 n 1 = P 1 V 1 /(RT 1 ) n 1 = mol Step 1: find n 1 Step 2: find n 2 Step 3: find g of B 2 H 6 G AS S TOICHIOMETRY What is the volume of oxygen gas at STP that would be needed for the complete combustion of 10.0g of octane (not balanced)?: C 8 H 18 + O 2 CO 2 + H 2 O g O mol O L K INETIC M OLECULAR T HEORY Recall: Kinetic Energy, KE = mv 2 What happens to KE when you increase velocity? What happens to the velocity of particles when you increase temperature? So, what happens to KE when you increase temperature? The average KE of a gas is DIRECTLY PROPORTIONAL to the temperature of the gas in KELVIN This is how the Kelvin scale works and why we use it! *KM theory only fully applies to ideal gases C OMBINED G AS L AW ( MINI ) L AB Read through lab and complete the two mini- experiments Answer all lab questions and problems at the end of the packet Begin homework problems D ALTON S L AW OF P ARTIAL P RESSURES T HE L AW For a mixture of gases in a container, the total pressure exerted is the sum of the partial pressures of the gases present. The partial pressure is the pressure that one gas would exert if it were alone in the container. So when you mix gases, their individual pressures do not change T HE L AW P total = P 1 + P 2 + P 3 PV= nRT P = Pressure exerted by an ideal gas is only affected by the NUMBER OF GAS PARTICLES Pressure is independent (not affected by) of the nature of the gas particles (volume, temp, etc) Pressure exerted by an ideal gas is only affected by the NUMBER OF GAS PARTICLES Pressure is independent (not affected by) of the nature of the gas particles (volume, temp, etc) Pressure exerted by an ideal gas is only affected by the NUMBER OF GAS PARTICLES Mixtures of helium and oxygen are used in the air tanks of underwater divers for deep dives. For a particular dive, 12L of O 2 at 25C and 1.0atm and 46L of He at 25C and 1.0atm were both pumped into a 5.0L tank. Calculate the partial pressure of each gas and the total pressure in the tank at 25C O2O2 More Practice, Pg. 441, #67 (this is a future hmwk problem)