CHE 101 Lecture outlines Chapter 10 Chapter 10 Gases Material to Learn on Your Own I do not have time to cover Sections 10 1 10 2 in lecture A Pre recorded lecture is located on UB Learns located Gulde Folder PreRecorded Folder Chapter10 IntroGases You MUST watch this prior to next lecture Turn to Page 3 Gas Laws of lecture Notes Gas Substances Air of many gases Common gases Usually have Noble gases Diatomics Ozone O3 Molecular compounds Ex CO CO2 N2O Solids or liquids can be forced to exist as gases called Ex H2O Physical Characteristics of Gases 1 Automatically take the of its container Molecules are in a gas than either a solid or a liquid Lots of between molecules 2 Highly Able to gases into volumes 3 Always make mixtures 1 CHE 101 Lecture outlines Chapter 10 Gases Exert Pressure Pressure P exerted by molecules in motion pulls atmospheric gases to Earth s surface Exerting psi lbs in2 Perspective car tires usually psi Felt How come we aren t crushed under this pressure Pressure our bodies this pressure SI Unit Pascal Pa Pascal proposed atmospheric pressure w altitude Other common units Atmospheres atm pressure at 1 atm 1 x105 Pa Millimeter of mercury mmHg from barometer Also known as torr Torricelli invented barometer 1 mmHg 1 torr 1 atm 760mmHg If increase Air Pressure Height 2 CHE 101 Lecture outlines Chapter 10 3 CHE 101 Lecture outlines Chapter 10 Gas Laws 4 variables describe gases Pressure P Volume V Temperature T Amount n of moles 1 Bolye s Law P V If pressure increases volume decreases P 1 V constant n and T PV constant 2 Charles s Law V T If increase temp volume increases Think hot air balloon V T constant n and P V T constant Temp must be in Kelvin 3 Avogadro s Law V n NOTE 1st proposed by Louis Gay Lussac but better interpreted by Amedeo Avogadro If increase moles volume increases Think blowing up a balloon V n constant T and P V n constant 4 CHE 101 Lecture outlines Chapter 10 5 CHE 101 Lecture outlines Chapter 10 Gas Constant What is the constant in each Gas Law 1 Boyle s 2 Charles s 3 Avogadro s PV constant V T constant V n constant Ideal universal gas constant R How do you know which to use Depends on the units Rewritten PV R V TR V nR L atm R 0 08206 mol K or J R 8 314 mol K Ideal Gas Law Combines all 3 gas laws into 1 PV nRT Required units for this equation P atm V L n moles T K TK TC 273 Question 10 1 Which value of the gas constant should always be used with the Ideal Gas Law A 0 08206 B 8 314 6 CHE 101 Lecture outlines Chapter 10 Standard Temp Press FOR GASES Standard Temperature Pressure special set of conditions Temperature 0oC Pressure 1 00 atm If have 1 00 mole of gas at STP what is the volume Standard molar volume 22 4L Sample Problem If 12 3g of steam is confined to 18 0 mL what is the temp C if the pressure is 1 75x106 torr PV nRT 12 3 g H2O 18 02 g 683 mols H2O 18 mL 0180 L 1 75x10 6 Torr 2 30x10 3 atm T 2300 atm 0180 L 683 mol 0 0826 T 739K 466oC 7 CHE 101 Lecture outlines Chapter 10 8 CHE 101 Lecture outlines Chapter 10 Combined Gas Law Combined Gas Law shows relationships for the gas at different Use Ideal gas equation make a Solve for what s set that to each other PV nRT GENERIC example Sample Problem A 5 50 L volume of gas has a pressure of 0 950 atm at 25 C What is the volume if the gas is at STP Question 10 2 The pressure in a balloon is maintained at 2 20 atm On a day when the temperature is 15 C the volume of gas in the balloon is 3 25x103 m3 What is the volume of the same quantity of gas on a day when the temperature is 31 C Which equation is best to use A PV nRT C B D 9 CHE 101 Lecture outlines Chapter 10 Molar Mass Ideal Gas Law Exp 10 Can find Molar mass Mm of unknown gas Mm grams m units Mm solve for n mol n Substitute into Eq PV nRT Solve for Mm Density Ideal Gas Law Can also determine the density of a gas d m V Close look at Mm eq Solve for d Note correlation when P T are constant Mm the the density Picture conditions 1atm 15 C 10 CHE 101 Lecture outlines Chapter 10 Sample Problem 1 What is the density of CO2 at 745 torr and 65 C Gases in Chemical Rxns Stoichiometry Use to relate information between reactants products Note to use gas law compound MUST BE a 11 CHE 101 Lecture outlines Chapter 10 Sample Problems 1 Air bags in cars are inflated by the decomposition of solid sodium azide NaN3 to form nitrogen gas If 74 0g NaN3 at 26 C decomposes resulting in an air bag having a volume of 36L what is the resulting gas pressure 2NaN3 s 2Na s 3N2 g 2 If 3 07L of oxygen gas at 0 993atm burns with liquid methane CH4 in a 250 0mL flask to produce carbon dioxide and liquid water at 297K what is the pressure of CO2 that is produced 12 CHE 101 Lecture outlines Chapter 10 Gas Mixtures Gases usually found as ie Air Partial Pressure each gas in a mixture exerts its own pressure John Dalton 1803 lifelong study of Dalton s Law total pressure PT of a mixture of gases is the of the partial pressures of the individual gases Ex ALL containers are 5L What if don t have partial pressures P1 or P2 Could solve for in for each gas Factor out b c they are constant Resulting in another way to solve for PT 13 CHE 101 Lecture outlines Chapter 10 Each gas contributes a portion or of the total number of moles in a mixture The more larger the gas has in the mixture the a greater the pressure and b greater the contribution to the pressure Mole fraction X of moles of one gas to the total X 1 n1 nT Relate partial total pressure 14 CHE 101 Lecture outlines Chapter 10 Sample Problems 1 6 00g O2 g is mixed with 0 841 atm of Ne g in a 15 0 L vessel at 0 C What is the partial pressure of O2 gas and what is the total pressure in the vessel 2 If you have 78 0 mols N2 and 21 0 mols O2 what are the partial pressures of these two gases at 760 torr 15 CHE 101 Lecture outlines Chapter 10 3 If one reacts a pressure of 70 0 atm of H2 and 30 0 atm of N2 into a 10 0 L reactor at 100 C how …