1 Notes on Gases: A Summary of Chapters 13 & 14 Section 1: Properties of Gases Section 2: Gas Laws Section 3: Gas Stoichiometry

2 Gas Properties Kinetic Molecular Theory: 1)Gases consist of large numbers of particles that are far apart. 2)When particles collide, they do not lose energy. 3)Gas particles are in continuous, rapid, random motion. 4)There are no forces of attraction between gas particles. 5)Average temperature of a gas depends on the temperature.

3 More Properties… Expansion: -No definite shape or volume. Gases naturally expand to fill their containers. Fluidity: Gas particles glide past one another causing them to “flow” like liquids. (Liquids and gases are FLUIDS.)

4 More Properties… Low Density: Particles are so far apart compared to solids and liquids the density is really low…therefore, gases float! Compressibility: Gas particles can be squeezes closer together (causing the volume to decrease and the pressure to increase).

5 More Properties… Diffusion: Natural mixing of gas particles caused by random motion. Effusion: Process of gas particles passing through a tiny opening. Ex. – Hole in a bike tire.

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7 What is Pressure? Pressure (P) is the force applied over a surface area. Measured in newtons (N). P = force area Barometers are used to measure atmospheric pressure. Measured in… 1.Millimeters of mercury (mm Hg) 2.Atmospheres (atm) 3.Torricelli (torr) *invented the barometer* 4.Pascal (Pa) or kilopascal (kPa)

8 Units for Pressure (All calculations must be in atm!!!) Atmospheric pressure at sea level: 1 atm = 760 mm Hg = 760 torr = kPa Units for Temperature (All calculations must be in Kelvin!!!) Converting from Kelvin  Celsius C = K – 273 Converting from Celsius  Kelvin K = C + 273

9 Standard Temperature and Pressure Oftentimes, chemists want to use the same conditions for several experiments…so a standard temperature and pressure was agreed upon. STP = 0 ºC and 1 atm

10 The Gas Laws 1.Boyle’s Law (Pressure-Volume) 2.Charles’s Law (Temperature-Volume) 3.Gay-Lussac’s Law (Temperature-Pressure) 4.Combined Gas Law (P-T-V) 5.Ideal Gas Law (P-T-V-Moles)

11 Boyle’s Law (Pressure-Volume) P 1 V 1 = P 2 V 2 If pressure increases, volume will ________. If pressure decreases, volume will ________. This relationship is ________.

12 Boyle’s Law (Pressure-Volume) P 1 V 1 = P 2 V 2 If pressure increases, volume will decrease. If pressure decreases, volume will increase. This relationship is inverse. Lungs Video Marshmallows Video

13 Charles’s Law (Temperature-Volume) V 1 = V 2 T 1 T 2 If temperature increases, volume will _______. If temperature decreases, volume will _______. This relationship is ________.

14 Charles’s Law (Temperature-Volume) V 1 = V 2 T 1 T 2 If temperature increases, volume will increase. If temperature decreases, volume will decrease. This relationship is direct. Liquid Nitrogen + Balloon 55-Gallon Can

15 Gay-Lussac’s Law (Temperature-Pressure) P 1 = P 2 T 1 T 2 If temperature increases, pressure will ______. If temperature decreases, pressure will ______. This relationship is ________.

16 Gay-Lussac’s Law (Temperature-Pressure) P 1 = P 2 T 1 T 2 If temperature increases, pressure will increase. If temperature decreases, pressure will decrease. This relationship is direct. Fountain Egg + Bottle

17 Wouldn’t it be easier if we only had one formula? COMBINED GAS LAW P 1 V 1 = P 2 V 2 T 1 T 2 If one of these variables is constant, block it out and use the equation that is left. If temperature is constant (no T) = Boyle’s Law If pressure is constant (no P) = Charles’s Law If volume is constant (no V) = Gay-Lussac’s Law

18 Summary of Formulas Boyle’s Law : P 1 V 1 = P 2 V 2 Charles’s Law : V 1 = V 2 T 1 T 2 Gay-Lussac’s Law : P 1 = P 2 T 1 T 2 Combined Gas Law : P 1 V 1 = P 2 V 2 T 1 T 2

19 PRACTICE – 1 of 4 COMBINED GAS LAW P 1 V 1 = P 2 V 2 T 1 T 2 Q1: A sample of Neon gas occupies a volume of 752mL at 25ºC. What volume will the gas occupy at 50ºC if the pressure remains constant? What law will we use?

20 PRACTICE – 2 of 4 COMBINED GAS LAW P 1 V 1 = P 2 V 2 T 1 T 2 Q2: A sample of oxygen gas has a volume of 150.mL when its pressure is 0.947atm. What will the volume of the gas be if the pressure increases to 0.987atm? (Temperature remains constant.) What law will we use?

21 PRACTICE – 3 of 4 COMBINED GAS LAW P 1 V 1 = P 2 V 2 T 1 T 2 Q3: The gas in an aerosol can is at a pressure of 3.00atm at 25ºC. Directions on the can warn the user not to keep the can in a place when the temperature exceeds 52ºC. What would the pressure in the can be at 52ºC? (Assume volume remains constant.) What law will we use?

22 PRACTICE – 4 of 4 COMBINED GAS LAW P 1 V 1 = P 2 V 2 T 1 T 2 Q4: A helium-filled balloon has a volume of 50.0L at 25ºC and 1.03atm. What volume will it have at 0.855atm and 10ºC ? What law will we use?

23 The Ideal Gas Law A law relates pressure, volume, temperature, and the number of moles of a gas. PV = nRT P = pressure (in atm) V = volume (in L) n = number of moles (in moles) R = Ideal Gas Constant ( always) T = temperature (in Kelvin)

24 PRACTICE – 1 of 3 Ideal Gas Law PV = nRT Q1: What is the pressure (in atm) exerted by a mol sample of nitrogen gas in a 10.0L container at 298K?

25 PRACTICE – 2 of 3 Ideal Gas Law PV = nRT Q2: What is the volume (in liters) of moles of oxygen gas at 20.0ºC and atm of pressure?

26 PRACTICE – 3 of 3 Ideal Gas Law PV = nRT Q3: How many moles of chlorine (Cl 2 ) is contained in a 10.0L tank at 27ºC and 3.50atm of pressure?

27 Final Summary of Formulas Boyle’s Law : P 1 V 1 = P 2 V 2 Charles’s Law : V 1 = V 2 T 1 T 2 Gay-Lussac’s Law : P 1 = P 2 T 1 T 2 Combined Gas Law : P 1 V 1 = P 2 V 2 T 1 T 2 Ideal Gas Law : PV = nRT

28 FINAL SECTION: Gas Stoichiometry Same rules as Reaction Stoichiometry… We are simply adding one value – standard molar volume. The volume occupied by one mole of gas at STP (Standard Temperature and Pressure) L/mol standard molar volume = 22.4 L/mol of gas.

29 PRACTICE – 1 of 4 Gas Stoichiometry Q1: A chemical reaction produces mol of oxygen gas. What volume (in liters) is occupied by the gas at STP? (Remember the value 22.4L/mol.)

30 PRACTICE – 2 of 4 Gas Stoichiometry Q2: A chemical reaction produced 98.0 mL of sulfur dioxide gas (SO 2 ) at STP. What was the mass in grams of the gas produced? (Remember the value 22.4L/mol.)

31 PRACTICE – 3 of 4 Gas Stoichiometry CaCO 3  CaO + CO 2 Q3: How many grams of calcium carbonate must be decomposed to produce 5.00L of carbon dioxide gas at STP? (Use PV=nRT)

32 PRACTICE – 4 of 4 Gas Stoichiometry WO 3 (s) + 3H 2 (g)  W (s) + H 2 O (l) Q4: How many liters of hydrogen gas at 35ºC and atm are needed to react completely with 875 g of tungsten oxide? (PV=nRT)

33 YouTube Videos – GAS HELP 1. Gas Stoichiometry #1Gas Stoichiometry #1 2. Gas Stoichiometry #2Gas Stoichiometry #2 3. Molar Volume ExplanationMolar Volume Explanation 4. How to Collect a Gas ExperimentallyHow to Collect a Gas Experimentally 5. Ideal Gas Law ExampleIdeal Gas Law Example 6. Diffusion of Gas DemosDiffusion of Gas Demos 7. Effusion of Heavy Gas (Sulfur hexafluoride)Effusion of Heavy Gas (Sulfur hexafluoride) 8. Effusion of Light Gas (Hydrogen)Effusion of Light Gas (Hydrogen) 9. Kinetic Molecular Theory of GasesKinetic Molecular Theory of Gases 10. Properties of GasesProperties of Gases

34 Review Topics for the Test I.Properties of Gases a) Kinetic Molecular Theory (5 parts) b) Fluidity, Expansion c) Compressibility, Density d) Effusion/Diffusion e) Units for Temperature and Pressure f) STP

35 Review Topics for the Test II. Gas Laws Boyle’s Law : P 1 V 1 = P 2 V 2 Charles’s Law : V 1 = V 2 T 1 T 2 Gay-Lussac’s Law : P 1 = P 2 T 1 T 2 Combined Gas Law :P 1 V 1 = P 2 V 2 T 1 T 2 Ideal Gas Law : PV = nRT

36 Review Topics for the Test III. Gas Stoichiometry Converting from moles  Liters Converting from Liters  moles Converting from grams  Liters Converting from Liters  grams Using a balanced equation to predict grams or Liters by using PV=nRT

37 Remember: - Scientific Calculator - Pencil - Scratch paper - 3x5 Note Card (front/back)