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G ASES Chapters 12.1 and 13. 12.1 Main Idea Gases expand, diffuse, exert pressure, and can be compressed because they are in a low-density state consisting.

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Presentation on theme: "G ASES Chapters 12.1 and 13. 12.1 Main Idea Gases expand, diffuse, exert pressure, and can be compressed because they are in a low-density state consisting."— Presentation transcript:

1 G ASES Chapters 12.1 and 13

2 12.1 Main Idea Gases expand, diffuse, exert pressure, and can be compressed because they are in a low-density state consisting of tiny, constantly moving particles

3 Objectives Predict the behavior of gases using the kinetic-molecular theory Explain how mass affects the rates of diffusion and effusion Calculate the partial pressure of a gas Measure gas pressure

4 Review Vocabulary Kinetic energy Molar mass

5 New Vocabulary Kinetic-molecular theory Elastic collision Temperature Diffusion Graham’s Law Pressure Barometer Manometer Pascal (Pa) Dalton's law of partial pressure Atmosphere (atm)

6 Kinetic-Molecular (KM) Theory Assumptions – Particle size is very small Particles take up relatively no space – Particles are far apart Very little interaction of particles – Collisions are elastic No kinetic energy is lost in a collision

7 Particle Energy Determined by mass and velocity Temperature- the average kinetic energy of particles in matter

8 Behavior of Gases Pressure- gases will expand to fill the space they occupy

9 Behavior of Gases Compression and expansion- density of material can be changed by changing the available volume

10 Behavior of Gases Diffusion- movement of one material through another – Concentration gradient – Effusion- gas escaping from a confined space through tiny openings –

11 What is the ratio of the rate of diffusion for ammonia and hydrogen chloride?

12 Calculate the ratio of effusion rates for nitrogen gas and neon R H /R He = 0.849

13 Pressure Pressure (P) is defined as the force per unit area on a surface. (P=F/A) Gas pressure is caused by collisions of the gas molecules with each other and with surfaces with which they come into contact. The pressure exerted by a gas depends on volume, temperature, and the number of molecules present. – The greater the number of collisions of gas molecules, the higher the pressure will be.

14 Gas Pressure Barometer – Barometers measure atmospheric pressure – open system Manometer – Manometers measure gas pressure in a closed system

15 Gas Pressure Units – Pascal (1 Pa = 1 /m 2 ) – Atmosphere (1 atm = kPa) – mm Hg (1 atm = 760 mm Hg) – Torr (1 torr = 1 mm Hg)

16 Dalton’s Law of Partial Pressures total pressure is the sum of the partial pressures P tot =P 1 + P 2 + P 3 + … P n

17

18 A mixture of O 2, CO 2 and N 2 has a total pressure of 0.97 atm. What is the partial pressure of O 2 if the partial pressure of CO 2 is 0.70 atm and the partial pressure of N 2 is 0.12 atm? 0.97 atm = 0.70 atm atm + x X = 0.15 atm

19 Can you… Predict the behavior of gases using the kinetic-molecular theory Explain how mass affects the rates of diffusion and effusion Calculate the partial pressure of a gas Measure gas pressure

20 T HE G AS L AWS Chapter 13.1

21 13.1 Main Idea For a fixed amount of gas, a change in one variable- pressure, volume or temperature- affects the other two.

22 13.1 Objectives State the relationships among pressure, volume, temperature, and the amount of gas Apply gas laws to problems involving pressure, volume, temperature, and the amount of gas Create graphs of the relationships among pressure, volume, temperature, and the amount of gas Solve problems related to fixed amounts of gases

23 Review Vocabulary Scientific law Directly related Indirectly (inversely) related Kelvin

24 New Vocabulary Ideal gas Absolute zero Boyle’s law Charles’s law Gay-Lussac’s law Combined gas law

25 Ideal gas Non-existent, but assumes the following: – Completely elastic collisions – Particles occupy no volume – Large number of particles – No attractive or repellent forces between particles – Molecules are in completely random motion

26 Boyle’s Law Constants: amount of gas (n) and temperature (T) Boyle's Law in Motion

27 A diver blows a 0.75 L air bubble 10 m under water. As it rises, the pressure goes from 2.25 atm to 1.03 atm. What is the volume of the bubble at the surface? P 1 V 1 =P 2 V atm 1.03 atm 0.75 L = 1.6 L

28 Charles’s Law Constants: amount of gas (n) and pressure (P) Temperature is in Kelvin (K) K= C Charles' Law in Motion

29 A helium balloon in a closed car occupies a volume or 2.32 L at 40°C. If the temperature rises to 75°C, what is the new volume of the balloon? V 2 =V 1 T 2 /T K K 2.32 L = 2.58 L

30 Gay-Lussac’s Law Constants: amount of gas (n) and volume (V) T must be in Kelvin Gay-Lussac in Motion

31 The pressure of oxygen gas inside a canister is 5.00 atm at 25°C. the canister is placed in a cold environment where the temperature is -10°C; what is the new pressure in the canister? P 2 =P 1 T 2 /T K K 5.00 atm = 4.41 atm

32 Predict The relationship between pressure and amount of gas at a fixed temperature and volume Pressure-Moles relationship The relationship between volume and the amount of gas at a fixed temperature and amount of gas Volume-Moles relationship

33 Combined Gas Law Combination of Boyle’s, Charles’, and Gay- Lussac’s laws

34 A gas at 110 kPa and 30.0°C fills a flexible container with an initial volume of 2.00L. If the temperature is raised to 80.0°C and the pressure increases to 440 kPa, what is the new volume? 0.58 L

35 Gas Law Summary LawBoyle’sCharles’Gay-Lussac’sCombined Formula ConstantMoles, tempMoles, pressureMoles, volumeMoles Graphic VolumeTemperaturePressureVolumeTemperaturePressureVolumeTemperaturePressureVolumeTemperaturePressure

36 Can you… State the relationships among pressure, volume, temperature, and the amount of gas Apply gas laws to problems involving pressure, volume, temperature, and the amount of gas Create graphs of the relationships among pressure, volume, temperature, and the amount of gas Solve problems related to fixed amounts of gases

37 I DEAL G AS L AW 13.2

38 13.2 Main Idea The ideal gas law relates the number of particles to pressure, temperature, and volume

39 13.2 Objectives Relate the number of particles and volume using Avogadro’s principle Relate the amount of gas present to its pressure, temperature, and volume using the ideal gas law Compare and contrast the properties of real gases and ideal gases Solve problems using the ideal gas law

40 Review Vocabulary Mole Molar mass (M)

41 New Vocabulary STP Avogadro’s principle Molar volume Ideal gas constant (R) Ideal gas law

42 STP Standard temperature and pressure – Standard temperature °C = K – Standard pressure 1 atm = 760 torr = kPa

43 Avogadro’s Principle Equal volumes of (ideal) gases, at the same temperature and pressure, contain equal numbers of particles 1 mol gas = 22.4 L at STP

44 How much volume do the following gases fill at STP 1 mol CO 2 1 mol H 2 O 1 mol CH 4 1 mol Ne 2 mol He 1 mol O 2

45 Molar Volume The main component of natural gas used for home heating and cooking is methane (CH 4 ). Calculate the volume that 2.00 kg of methane will occupy at STP. M = m/n – M = molar mass – m = mass – n = number of moles

46 The main component of natural gas used for home heating and cooking is methane (CH 4 ). Calculate the volume that 2.00 kg of methane will occupy at STP. Molar mass (M) = g/mol (C + 4H)

47 The main component of natural gas used for home heating and cooking is methane (CH 4 ). Calculate the volume that 2.00 kg of methane will occupy at STP. Molar mass (M) = g/mol (C + 4H) Number of moles (n) = ?? M = m/n n = m/M 2000 g CH 4 1 mol = 125 mol g

48 The main component of natural gas used for home heating and cooking is methane (CH 4 ). Calculate the volume that 2.00 kg of methane will occupy at STP. Molar mass (M) = g/mol (C + 4H) Number of moles (n) = 125 mol 2000 g CH 4 1 mol = 125 mol g

49 The main component of natural gas used for home heating and cooking is methane (CH 4 ). Calculate the volume that 2.00 kg of methane will occupy at STP. Molar mass (M) = g/mol (C + 4H) Number of moles (n) = 125 mol Molar volume = ?? 125 mol22.4 L = 2800 L 1 mol

50 Ideal Gas Law PV=nRT – P = pressure (atm) – V = volume (L) – n = number of moles of gas (mol) – R = gas constant (L atm)/(mol K) – T = temperature (K)

51 Calculate the number of moles of ammonia gas contained in a 3.0 L vessel at 300 K with a pressure of 1.50 atm. P = 1.50 atm; V = 3.0 L; n = ?; T = 300 K R = (L atm)/(mol K) N= PV/RT 1.50 atm (mol K)3.0 L = 0.18 mol 300 K ( L atm)

52 Molar mass and density PV=nRT – n=m/M – PV=mRT/M – M=mRT/PV D=m/V – D=MV/RT

53 Ideal gas and Real gases Ideal gas Particles occupy no volume All collisions are perfectly elastic Infinitely large number of molecules No forces between molecules Real gas Particles occupy volume KE is lost during collisions Limited numbers of molecules Inter-molecular forces exist

54 Can you… Relate the number of particles and volume using Avogadro’s principle Relate the amount of gas present to its pressure, temperature, and volume using the ideal gas law Compare and contrast the properties of real gases and ideal gases Solve problems using the ideal gas law

55 G AS S TOICHIOMETRY 13.3

56 Main Idea When gases react, the coefficients in the balanced chemical equation represent both molar amounts and the relative volumes.

57 13.3 Objectives Determine volume ratios for gaseous reactants and products by using coefficients from chemical equations Apply gas laws to calculate amounts of gaseous reactants and products in a chemical reaction

58 Review Vocabulary Stoichiometry Coefficient Chemical equation

59 Stoichiometry with Gases Only works with gases! 2H 2 (g) + O 2 (g)  2 H 2 O (g) – 2 moles of hydrogen + 1 mole of oxygen react to form 2 moles of water – 2 liters of hydrogen + 1 liter of oxygen react to form 2 liters of water

60 What volume of oxygen gas is needed for the complete combustion of 4.00 L of propane gas assuming that pressure and temperature are constant? C 3 H 8 (g) + 5 O 2 (g)  3 CO 2 (g) + 4 H 2 O(g) 4.00 L C 3 H 8 = 20.0 L O 2 1 L C 3 H 8 5 L O 2

61 Can you… Determine volume ratios for gaseous reactants and products by using coefficients from chemical equations Apply gas laws to calculate amounts of gaseous reactants and products in a chemical reaction

62 Can you… Predict the behavior of gases using the kinetic-molecular theory Explain how mass affects the rates of diffusion and effusion Calculate the partial pressure of a gas Measure gas pressure State the relationships among pressure, volume, temperature, and the amount of gas Apply gas laws to problems involving pressure, volume, temperature, and the amount of gas Create graphs of the relationships among pressure, volume, temperature, and the amount of gas Solve problems related to fixed amounts of gases Relate the number of particles and volume using Avogadro’s principle Relate the amount of gas present to its pressure, temperature, and volume using the ideal gas law Compare and contrast the properties of real gases and ideal gases Solve problems using the ideal gas law Determine volume ratios for gaseous reactants and products by using coefficients from chemical equations Apply gas laws to calculate amounts of gaseous reactants and products in a chemical reaction


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