Common Gases PROPERTIES OF GASES. Gases and Environmental Concerns. Kinetic Theory of Gases

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1 Common Gases Of the elements on the periodic table, some exist as a gas at room temperature, these include the Noble Gases, Group 8A (18), Chapter PROPERTIES OF GASES H 2, N 2, O 2, F 2, Cl 2, and many oxides of nonmetals such as CO, CO 2, NO, NO 2, SO 2, and SO 3. 2 Gases and Environmental Concerns Some gases are responsible for environmental and health concerns including methane, CH 4 (green house gas, flammable, respiratory concerns) chlorofluorocarbons (CFCs) (destroys the ozone layer) nitrogen oxides found in smog (respiratory concerns) volatile organic compounds (VOCs), such as compounds found in paint thinners (just plain old really bad stuff) Kinetic Theory of Gases A gas consists of small particles that move randomly with high velocities. have essentially no attractive (or repulsive) forces toward each other. have a very small volume compared to the volume of the containers they occupy. are in constant motion. have kinetic energies that increase with an increase in temperature. 3 4

2 Properties of Gases Gases are described in terms of four properties: 1. pressure (P) 2. volume (V) 3. temperature (T) 4. amount (n) Chapter GAS PRESSURE 5 Gas Pressure Gas pressure is the force acting on a specific area. Pressure P Atmospheric Pressure Atmospheric pressure is the pressure exerted by a column of air from the top of the atmosphere to the surface of the Earth. has units of atm, mmhg, torr, lb/in. 2, and kilopascals(kpa). 1 atm = 760 mmhg (exact) 1 atm = 760 torr (exact) 1 atm = 14.7 lb/in. 2 1 atm = kpa 7 8

3 Atmospheric Pressure Altitude and Atmospheric Pressure Atmospheric pressure is about 1 atmosphere at sea level. depends on the altitude and the weather. is lower at high altitudes where the density of air is less. is higher on a rainy day than on a sunny day Barometer Barometer A barometer measures the pressure exerted by the gases in the atmosphere by the height of mercury in the column (mmhg). A barometer: The pressure exerted by the gases in the atmosphere is equal to the downward pressure of a mercury column in a closed glass tube. 11

4 Maximum Depth for Water is 29 feet Chapter PRESSURE AND VOLUME (BOYLE S LAW) BOYLE S LAW Robert William Boyle ( ) Born 25 January 1627 Lismore, County Waterford, Ireland Died 31 December 1691 (aged 64) London, England Nationality Irish Fields Physics, chemistry Education Eton College 15

5 Boyle s Law Boyle s law states that the pressure of a gas is inversely related to its volume when temperature (T) and amount of gas (n) are constant. if the pressure (P) increases, then the volume (V) decreases. PV Constant in Boyle s Law In Boyle s law, the product P V is constant as long as T and n do not change. P 1 V 1 = 8.0 atm x 2.0 L = 16 atm*l P 2 V 2 = 4.0 atm x 4.0 L = 16 atm*l it can be stated that since P V is a constant. P 1 V 1 = P 2 V 2 = constant (T, n constant) Boyle s Law and Breathing: Inhalation During inhalation, the lungs expand, the pressure in the lungs decreases, and air flows towards the lower pressure in the lungs. Boyle s Law and Breathing: Exhalation During exhalation, lung volume decreases, pressure within the lungs increases, and air flows from the higher pressure in the lungs to the outside

6 7.75 At a restaurant, a customer chokes on a piece of food. You put your arms around the person s waist and use your fists to push up on the person s abdomen, an action called the Heimlich maneuver. a. How would this action change the volume of the chest and lungs? b. Why does it cause the person to expel the food item from the airway? Chapter TEMPERATURE AND VOLUME (CHARLES LAW) Charles s Law Jacques Alexandre César Charles, 1820 Born November 12, 1746 Beaugency, Orléanais Died April 7, 1823 (aged 76) Paris Nationality France

7 Charles s Law Charles s law states that, the Kelvin temperature of a gas is directly related to the volume of the gas, P and n are constant, and = Constant Charles s Law: V and T Charles s law states that when the temperature of a gas increases, making the molecules move faster, the volume of the gas must increase to maintain constant pressure. as the temperature of a gas increases, the molecules move faster and its volume increases to maintain constant P Gay-Lussac s Law Chapter TEMPERATURE AND PRESSURE (GAY-LUSSAC S LAW) Joseph Louis Gay-Lussac Born 6 December 1778 Saint-Léonard-de-Noblat Died 9 May 1850 (aged 71) Paris, France Nationality French Fields Chemistry

8 Gay-Lussac s Law: P and T Gay-Lussac s law states that the pressure exerted by a gas is directly related to the Kelvin temperature. V and n are constant. an increase in temperature increases the pressure of a gas. = Constant A fire extinguisher has a pressure of 10. atm at 25 C. What is the pressure, in atmospheres, if the fire extinguisher is used at a temperature of 75 C and V and n remain constant? 7.81 A sample of hydrogen (H 2 ) gas at 127 C has a pressure of 2.00 atm. At what temperature ( C) will the pressure of the H 2 decrease to 0.25 atm, if V and n remain constant? P T P T 10 atm K P K 348 K 298 K 10 atm P P 12 atm P P T T 2.00 atm 0.25 atm K T 0.25 atm 2.00 atm 400 K T T 50 K 220

9 7.82 A sample of nitrogen (N 2 ) gas has a pressure of 745 mmhg at 30. C. What is the pressure when the temperature rises to 125 C? Vapor Pressure In a closed container, the vapor above a liquid accumulates and creates pressure called vapor pressure. P T P T 745 mm Hg K P K 398 K 303 K 745 mm Hg P P 979 mm Hg Each liquid exerts its own vapor pressure at a given temperature. As temperature increases, more vapor forms, and vapor pressure increases. 36 Vapor Pressure and Boiling Point Boiling Point of Water A liquid reaches its boiling point when its vapor pressure becomes equal to the external pressure. The boiling point of water depends on the vapor pressure. is lower at higher altitudes. is increased by using an autoclave to increase external pressure

10 Chapter THE COMBINED GAS LAW Combined Gas Law The combined gas law uses Boyle s Law P 1 V 1 = P 2 V 2 = constant Charles s Law Gay-Lussac s Law = constant = constant P V T P V T

11 Combined Gas Law The combined gas law: = constant Combined Gas Law By using the combined gas law, we can derive any of the gas laws by omitting those properties that do not change. 44 Review Gas Laws Boyles Law Constant Temperature PV = constant Charles Law Constant Pressure V/T = constant Gay Lussacs Law Constant Volume P/T = constant Combined Gas Law PV/T = constant Ideal Gas Law PV=nRT Constant Amount of Gas P V P V T T Remember 1 atm = 760 mmhg atm 425 ml K atm atm V 2170 ml atm V K 178 K 297 K 425 ml V 7.78 Your spaceship has docked at a space station above Mars. The temperature inside the space station is a carefully controlled 24 C at a pressure of 745 mmhg. A balloon with a volume of 425 ml drifts into the airlock where the temperature is 95 C and the pressure is atm. What is the new volume, in milliliters, of the balloon if n remains constant and the balloon is very elastic?

12 7.80 A weather balloon has a volume of 750 L when filled with helium at 8 C at a pressure of 380 torr. What is the new volume of the balloon when the pressure is 0.20 atm, the temperature is 45 C, and n remains constant? P V P V T T Remember 1 atm = 760 mmhg 380 torr 750 L K 380 torr 150 torr V 1,600L torr V K 228 K 281 K 750L V Chapter VOLUME AND MOLES (AVOGADRO S LAW) Avogadro s Law: Volume and Moles Avogadro s Law Avogadro s law states that the volume of a gas is directly related to the number of moles (n) of gas. T and P are constant. = constant 49 Amedeo Avogadro Born 9 August 1776 Turin, Piedmont-Sardinia Died 9 July 1856 (aged 79) Turin, Piedmont-Sardinia Nationality Italian

13 STP Molar Volume To make comparisons between different gases, we use arbitrary conditions called standard temperature (273 K) and standard pressure (1 atm). Standard temperature and pressure is abbreviated as STP. The molar volume of a gas measured at STP (standard temperature and pressure) is 22.4 L for 1 mole of any gas. Standard temperature (T) = 0 C or 273 K Standard pressure (P) = 1 atm (760 mmhg) 51 Avogadro s law indicates that 1 mole of any gas at STP has a volume of 22.4 L. 52 Molar Volume as a Conversion Factor Gases in Chemical Reactions The molar volume at STP has about the same volume as 3 basketballs. can be used to form 2 conversion factors. The volume or amount of a gas at STP in a chemical reaction can be calculated from STP conditions L 1 mole and 1 mole 22.4 L mole mole factors from the balanced equation

14 7.87 When heated, calcium carbonate decomposes to give calcium oxide and carbon dioxide gas. If 56.0 g of CaCO 3 react, how many liters of CO 2 gas are produced at STP? 7.88 Magnesium reacts with oxygen to form magnesium oxide. How many liters of oxygen gas at STP are needed to react completely with 8.0 g of magnesium? CaCO 3(s) CaO (s) + CO 2(g) 2Mg (s) + O 2(g) 2MgO (s) CaCO CaO CO n 56.0 gcaco 1 mole CaCO 100 g CaCO moles CaCO moles CaCO moles CO moles moles CO 22.4 L 1 mole 12.5 L CO 2Mg O 2MgO 1 mole Mg n 8.0 g Mg 0.33 moles Mg 24.3 g Mg 2 moles Mg 1 moles O 0.16 moles O 22.4 L 0.16 moles O 1mole 3.8LO 7.89 In the Haber process, H 2 and N 2 react to produce ammonia (NH 3 ). How many grams of N 2 are needed to produce 150 L of ammonia at STP? 7.90 How many liters of H 2 gas at STP can be produced from the reaction of 2.45 g of Al with excess HCl? 2Al (s) + 6HCl (aq) 2AlCl 3(aq) + 3H 2(g) 3H 2(g) + N 2(g) 2NH 3(g) 3H N 2NH 1 mole 150 L NH 22.4 Liters 6.7 moles NH 1 moles N 6.7 moles NH 3.3 moles N 2 moles NH 3.3 moles N 28.0 grams N 1 mole N 94 grams N 2Al 6HCl 2AlCl 3H 1 mole Al 2.45 g Al moles Al 27.0 g Al moles Al 3 moles H 2 moles Al moles H 22.4 Liters moles H 3.05LH 1mole

15 7.91 Aluminum oxide can be formed from its elements. What volume, in liters, of oxygen at STP is needed to completely react 5.4 g of Al? 7.92 Glucose, C 6 H 12 O 6, is metabolized in living systems to CO 2 and H 2 O. How many grams of water can be produced from 12.5 L of O 2 at STP? 4Al (s) + 3O 2(g) 2Al 2 O 3(s) C 6 H 12 O 6(s) + 6O 2(g) 2CO 2(g) + 6H 2 O (l) 5.4 g Al 4Al 3O 2Al O 1 mole Al 27.0 g Al 3 moles O 4 moles Al 22.4 L O 1 mole O 3.4LO C H O 6O 2CO 6H O 12.5 L O 1 mole O 6molesH O 18.0 g H O 10.0 g 22.4 L O 6molesO 1moleH O 7.94 What is the molar mass, g/mole, of a gas if 1.15 g of the gas has a volume of 225 ml at STP? 7.95 Nitrogen dioxide reacts with water to produce oxygen and ammonia. How many liters of O 2 are produced when 0.42 mole of NO 2 reacts at STP? 4NO 2(g) + 6H 2 O (g) 7O 2(g) + 4NH 3(g) L 1 mole moles 22.4 L Molar Mass Grams Mole 1.15 grams moles 114 grams mole 4NO 0.42 mole NO 6H O 7O 4NH 7 moles O 22.4 L O 16LO 4 moles NO mole O

16 7.96 What is the volume, in liters, of H 2 gas produced at STP from the reaction of 25.0 g of Al? 2Al (s) + 3H 2 SO 4(aq) Al 2 (SO 4 ) 3(aq) + 3H 2(g) 7.97 A weather balloon is partially filled with helium to allow for expansion at high altitudes. At STP, a weather balloon is filled with enough helium to give a volume of 25.0 L. How many grams of helium were added to the balloon? 25.0 g Al 2Al 3H SO Al SO 3H 1 mole Al 27.0 grams Al 3 moles H 2 moles Al 22.4 L H 1 mole H 31.1 L H 25.0 L He 1 mole He 4.00 g He 22.4 L He 1moleHe 4.46gHe Ideal Gas Law Chapter THE IDEAL GAS LAW The four properties used in the measurement of a gas, pressure (P), volume (V), temperature (T), and amount (n), can be combined to give a single expression called the ideal gas law. PV = nrt 70

17 R, Ideal Gas Constant Unit Summary for R, the Ideal Gas Constant PV nrt Rearranging the ideal gas law equation shows that the four gas properties equal a constant, R. PV nt = R To calculate the value of R, we substitute the STP conditions for molar volume into the expression: R atm L 1 mole 273 K L atm mole K In 1783, Jacques Charles launched his first balloon filled with hydrogen gas, which he chose because it was lighter than air. The balloon had a volume of 31,000 L when it reached an altitude of 1000 m, where the pressure was 658 mmhg and the temperature was 8 C. PV nrt n PV How many kilograms of hydrogen RT were used to fill the balloon at STP? 658 mm Hg 31,000 L 1 atm n atm L mole K K 760 mm Hg 1,200 moles 1,200 moles H 2.0 g H 1 kg 1 mole H 1,000 g 2.4 KgH n PV nrt n PV RT 1.2 atm 35.0L atm L K mole K n 1.8moles 7.83 How many moles of CO 2 are in 35.0 L of CO 2(g) at 1.2 atm and 5 C?

18 7.84 A container is filled with 0.67 mole of O 2 at 5 C and 845 mmhg. What is the volume, in milliliters, of the container? 7.85 A 2.00 L container is filled with methane gas (CH 4 ) at a pressure of mmhg and a temperature of 18 C. How many grams of methane are in the container? V PV nrt V nrt P 0.67 mole atm L mole K K 845 mm Hg 760 mm Hg/atm V 14 L V 14,000 ml PV nrt n PV RT mm Hg 2.00 L 1 atm n moles atm L mole K K 760 mm Hg moles CH 16.0 g CH 1kg 1moleCH 1,000 g 4.40gCH P PV nrt P nrt V n 50.0 gn 1 mole N 28.0 g N 1.79 moles atm L 1.79 moles mole K 15.0 L P 2.91 atm 7.86 A steel cylinder with a volume of 15.0 L is filled with 50.0 g of nitrogen gas at 25 C. What is the pressure, in atmospheres, of the N 2 gas in the cylinder? K PV nrt n PV RT 748 torr 0.941L n 1 atm moles atm L mole K K 760 torr Molar Mass Grams 1.62 grams Mole moles 42.1 grams mole 7.93 A sample of gas with a mass of 1.62 g has a volume of 941 ml at a pressure of 748 torr and a temperature of 20 C. What is the molar mass, g/mole, of the gas?

19 7.98 At an altitude of 30.0 km, where the temperature is 35 C, a weather balloon containing 1.75 moles of helium has a volume of 2,460 L. What is the pressure, in mmhg, of the helium inside the balloon? P PV nrt P nrt V atm L 1.75 moles K mole K atm 2,460 L atm 760 mm Hg 10.6 mm Hg 1 atm Chapter PARTIAL PRESSURES (DALTON S LAW) Partial Pressure, Dalton s Law In a gas mixture, each gas exerts its partial pressure, which is the pressure it would exert if it were the only gas in the container. Dalton s Law of Partial Pressures Dalton s Law of Partial Pressures indicates that pressure depends on the total number of gas particles. P He = 2.0 atm P Ar = 4.0 atm P total = P He + P Ar = 2.0 atm atm = 6.0 atm Dalton s law states that the total pressure of a gas mixture is the sum of the partial pressures of the gases in the mixture. P P P + P 81 82

20 Total Pressure For example, at STP, one mole of a pure gas will exert the same pressure as one mole of a gas mixture in a 22.4 L container. V = 22.4 L Gas mixtures Composition of Air Air is a mixture of gases, including nitrogen, oxygen, carbon dioxide, argon, and water gases. 1.0 mole N mole O mole He 1.0 mole 0.5 mole O mole He 0.2 mole Ar 1.0 mole 1.0 atm 1.0 atm 1.0 atm Blood Gases Blood Gases In the lungs, O 2 enters the blood, at the same time that CO 2 is released. In the tissues, O 2 enters the cells, which release CO 2 into the blood. In the body, O 2 flows into the tissues because the partial pressure of O 2 is higher in blood and lower in the tissues. CO 2 flows out of the tissues because the partial pressure of CO 2 is higher in the tissues and lower in the blood. Partial Pressures (mmhg) in Blood and Tissue Gas Oxygenated Deoxygenated Tissues Blood Blood O mmhg 40 mmhg 30 mmhg or less CO 2 40 mmhg 46 mmhg 50 mmhg or greater 86

21 Changes in Partial Pressures of Blood Gases During Breathing 7.76 An airplane is pressurized to 650. mmhg. a. If air is 21% oxygen, what is the partial pressure of oxygen on the plane? 650 mm Hg x 21% O 140 mm Hg is the partial pressure of O b. If the partial pressure of oxygen drops below 100. mmhg, passengers become drowsy. If the total cabin pressure is lowered this happens and oxygen masks are released. What is the total cabin pressure at which oxygen masks are dropped? mm O 21% O 480 mm Hg total cabin pressure 7.99 A gas mixture contains oxygen and argon at partial pressures of 0.60 atm and 425 mm Hg. If nitrogen gas added to the sample increases the total pressure to 1,250 torr, what is the partial pressure, in torr, of the nitrogen added? A gas mixture contains helium and oxygen at partial pressures of 255 torr and atm. What is the total pressure, in mmhg, of the mixture after it is placed in a container onehalf the volume of the original container? 760 torr Partial Pressure due to O 0.60 atm 460 torr 1 atm 1 torr Partial Pressure due to Ar 425 mm Hg 425 torr 1mmHg Partial Pressure due to N 1, torr 360 torr 1 mm Hg Partial Pressure due to He 255 torr 255 mm Hg 1 torr 760 mm Hg Partial Pressure due to O atm 342 mm Hg 1 atm Total Pressure original container mm Hg 597 mm Hg P V P V If the volume is cut in half, then the pressure will be doubled Total Pressure half container mm Hg 1190 mm Hg

22 SLO Student Learning Objectives Class Learning Objectives: Conceptualize, model and explain chemical processes qualitatively at the molecular level. Extract appropriate information, analyze and synthesize experimental results to reach correct conclusions. Perform laboratory techniques safely and accurately and maintain a laboratory notebook according to standard scientific guidelines. College Student Learning Objectives: Written and Oral Communication Problem Solving Math Competency Assessment Method: Embedded questions in exams. Evaluation of lab reports and lab notebooks. Regarding the test covering chapters 7, 8 & 10 Stuff that will be provided 1 gram = ounces 1 kg = 2.20 lbs (exact) 2.54 cm = 1 inch (exact) 1 liter = 1.06 quarts 1 ml = 1 cm3 (exact) 1 ml H 2 O = 1 g (exact) 1 cal = 1 g C for water (exact) T F = 1.8Tc + 32 (exact) 1 cal = joules Carbohydrate 4 kcal/g Fat 9 kcal/g Protein 4 kcal/g 1 atm = 760 mm Hg R = atml/molek 22.4L = 1 mole at STP A periodic Table Solubility Rules Someone needs to me. All the paper you will need Stuff you need to bring A writing instrument A calculator Did I miss anything? And Finally The final is on Thursday May 31 st in this classroom at 5:30 PM Please get sleep the night before the final. Please eat decent food before the test. Please relax and take you time during the final. Grades will be sent out in approximately two weeks. Thank you each and every one on you. You have greatly enriched my life by attending these classes. I hope that you continue your education and are successful in life. Sincerely, Prof.M.