1 / 37

Unit 10: Gases

Unit 10: Gases. Chapter 14 Chemistry 1L Cypress Creek High School. Table of Contents. Chapter 14: Gases 14.4: Gas Stoichiometry 14.1: KMT 14.2: The Combined Gas Laws 14.3: The Ideal Gas Law. 14.4. Gas Stoichiometry. The Mole. 14.4. Gas Stoichiometry. Avogadro’s Principle.

anja
Télécharger la présentation

Unit 10: Gases

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Unit 10: Gases Chapter 14 Chemistry 1L Cypress Creek High School

  2. Table of Contents • Chapter 14: Gases • 14.4: Gas Stoichiometry • 14.1: KMT • 14.2: The Combined Gas Laws • 14.3: The Ideal Gas Law

  3. 14.4 Gas Stoichiometry The Mole

  4. 14.4 Gas Stoichiometry Avogadro’s Principle • Don’t forget that Mole Ratios indicate the molar relationship between two chemicals in an equation • In the early 1900s, Avogadro proposed that equal volumes of gases at the same conditions contain the same number of particles. • Avogadro’s principle states that one mole (6.02 x 1023 particles) of any gas at STP occupies a volume of 22.4 L. • Avogadro’s principle allows you to interrelate mass, moles, pressure, volume, and temperature for any sample of gas.

  5. 14.4 Gas Stoichiometry Gas Stoichiometry • 1 mole = 22.4 L of a gas at STP • All stoichiometric calculations will be done at STP 2 2 2 . . .

  6. 14.4 Gas Stoichiometry STP • Standard temperature and pressure (STP) has been designated as: • Temperature at 273 K • Pressure at 1 atm • 1 mole = 22.4 L • Used to compare gases • Creates ideal conditions for describing behavior of gases.

  7. 14.4 Gas Stoichiometry Stoichiometric Calculations • There are three basic gas stoichiometric calculations: • mole-to-volume conversions • volume-to-volume conversions • mass-to-volume conversions. • All stoichiometric calculations begin with a balanced equation and mole ratios.

  8. 14.4 Gas Stoichiometry Mole-to-Volume Conversions • A zeppelin combusts H2 and O2 to form water. There are 25 moles of hydrogen gas in a zeppelin. How many liters of water vapor does it produce at STP? • Given: 25 moles X L H2 (g) + O2 (g)  H2O (g) • Equation: 1 mol 1*(22.4L) X L H2O = 25 mol H2 1*22.4 L H2O 1 mol H2 = 25 L H2O

  9. 14.4 Gas Stoichiometry Volume-to-Volume Conversions • When you are grilling steaks, how many liters of oxygen are required to burn 1.5 liters of propane in the reaction: C3H8 + 5O2 3CO2 + 4H2O? • Given: 1.5 L x L C3H8 + 5O2 3CO2 + 4H2O • Eq.: 1*(22.4L) 5*(22.4L) X L O2 = 1.5 L C3H8 5* 22.4L O2 1*22.4L C3H8 = 7.5 L O2

  10. The following reaction shows the production of ammonia. How many L of nitrogen are required to produce 85 grams of ammonia? Given: X L 85 g Equation: 1*(22.4L) 2*(17g) X L N2 = 85g NH3 1*22.4L N2 2*(17 g NH3) = 56 L NH3 Mass-to-Volume Conversions 14.4 Gas Stoichiometry

  11. 14.4 Gas Stoichiometry Gas Stoichiometry Practice • Ammonium sulfate can be prepared by a reaction between ammonia gas and sulfuric acid as follows. • What volume of NH3 gas, measured at 78°C and a pressure of 1.66 atm, will be needed to produce 5.00 x 103 g of (NH4)2SO4?

  12. 14.4 Gas Stoichiometry Gas Characteristics • Gases have no definite shape or volume • Gases diffuse rapidly • Gases have low density • Gases are compressible/expandable • Gases exert pressure on their containers

  13. 14.1 KMT Kinetic Molecular Theory • KMT explains the behavior of all matter (solids, liquids, and gases) at a particle level - kinetic means ‘motion’ • As related to gases, there are several basic principles of kinetic molecular theory (KMT): • Gas particles are in constant, random motion • Gas particles do not attract or repel each other • Gas particles have elastic collisions, meaning they do not lose kinetic energy when they collide • Gas particles’ kinetic energy depends on their temperature

  14. 14.1 KMT Physical Properties: Temperature • Temperature is a measure of the average kinetic energy of particles in a system • Different from heat - amount of energy in a system • Temperature is measured in units of: • Fahrenheit (oF) • Celsius (oC) • Kelvin (K) • Temperature is measured by a thermometer How does temperature change? As a result of its change, what does it effect?

  15. 14.1 KMT Physical Properties: Temperature • When working with gases, we never use Celsius – only Kelvin! • Converting Celsius to Kelvin • K = oC + 273 • Ex: Room temperature is about 22oC. In Kelvin, this would be 296 K. • Absolute Zero (0 Kelvin or -273oC) is the temperature at which all particle motion ceases • Absolute zero can never be achieved artificially, though it is possible to reach temperatures close to it through the use of cryocoolers.

  16. 14.1 KMT Physical Properties: Volume • Volume is the space matter occupies • Gases always occupy the volume of their container • Volume of gas is measured in units of liters (L) or milliliters (mL)  1 L = 1000 Ml • Gas volume can be expanded or compressed due to changes in… • Temperature • Pressure • Amount of particles • (mass or moles) • Describe the similarities and differences between the balloons. What accounts for their differences?

  17. 14.1 KMT Physical Properties: Pressure • Pressure is the force over a given area • If someone stepped on your foot, which shoe would you prefer they wore? • Pressure is measured in units of: • Atmospheres (atm) • Pascals (Newtons/m2) • psi (pounds per square inch) • mmHg (mm of Mercury) • Pressure is measured by: • Barometer • Manometer

  18. 14.1 KMT Physical Properties: Pressure • Gas pressure can be altered due to changes in… • Volume • Temperature • Amount of particles(mass or moles) • The more often gas particles collide with the walls of their container, the greater the pressure. Describe the similarities and differences between the two basketballs. What accounts for their differences? Click box to view movie clip.

  19. 14.1 KMT Dalton’s Law • The total pressure of a gas mixture is the sum of the partial pressures of each individual gas • Air is a mixture! I’m John Dalton

  20. 14.1 KMT Dalton’s Law • Ex: The pressure on a tank of air with… • 20.9 atm oxygen • 78.1 atm nitrogen • 0.97 atm argon • 1.28 atm water vapor • 0.05 atm carbon dioxide = 101.3 atm Ptotal = P1 + P2 + P3…

  21. 14.2 The Gas Laws Gas Laws • The gas laws apply to ideal gases, which are described by the kinetic theory in the following five statements. • Gas particles do not attract or repel each other. • Gas particles are much smaller than the spaces between them. • Gas particles are in constant, random motion. • No kinetic energy is lost when gas particles collide with each other or with the walls of their container. • All gases have the same kinetic energy at a given temperature. • The following laws explain the relationships between temperature, volume, and pressure:

  22. 14.2 The Gas Laws Boyle’s Law • Explains the effect pressure has on volume • Temperature stays constant • Inverse relationship • As pressure increases, volume decreases PV • As pressure decreases, volume increases PV V P I’m Robert Boyle

  23. 14.2 The Gas Laws Boyle’s Law • KMT connection: the less space particles have to move, the more forces they exert on each other

  24. 14.2 The Gas Laws Boyle’s Law Click box to view movie clip. • Practice: • If the pressure is tripled, what happens to the volume? • If the pressure is halved, what happens to the volume? • Example: • Squeezing syringe

  25. 14.2 The Gas Laws Charles’ Law • Explains the effect temperature has on volume • Pressure stays constant • Direct relationship • As temperature increases, volume increases TV • As temperature decreases, volume decreases TV V T I’m Jacques Charles

  26. 14.2 The Gas Laws Charles’ Law • KMT connection: the more avg. kinetic energy particles have, the greater the distance between particles

  27. 14.2 The Gas Laws Charles’ Law • Practice: • If the temperature is quadrupled, what happens to the volume? • If the temperature is decreased by 1/3, what happens to the volume? • Example: • Hot air balloon Click box to view movie clip.

  28. 14.2 The Gas Laws P P Gay-Lussac’s Law • Explains the effect temperature has on pressure • Volume stays constant • Direct relationship • As temperature increases, pressure increases TP • At higher temperatures, the particles in a gas have greater kinetic energy. • As temperature decreases, pressure decreases TP I’m Joseph Louis Gay-Lussac

  29. 14.2 The Gas Laws Gay-Lussac’s Law • KMT connection: the more avg. kinetic energy particles have, the more forces they exert on each other

  30. 14.2 The Gas Laws Gay-Lussac’s Law • Practice: • If the temperature is doubled, what happens to the pressure? • If the temperature is decreased by 1/4, what happens to the pressure? • Example: • Pressure cooker

  31. 14.2 The Gas Laws Combined Gas Law • The gas laws may be integrated into a single equation called the combined gas law • Where… • P = pressure in atm • V = volume in L • T = temperature in K • “1” means initial • “2” means final • Steps to solving • Assign variables • Convert oC to K (if necessary) • “Drop” constants (see example) • Solve problem

  32. 14.2 The Gas Laws Combined Gas Law • Example: In the fall, at a temperature of 32oC, you fill your tires to a pressure of 2.18 atm. A cold front blows through, with temperatures dropping to 5oC, and your tires become flat. Knowing that the volume of your tires has not changed, what is the new pressure of the tires? • P1 = 2.18 atm • V1 = constant • T1 = 32oC + 273 = 305 K • P2 = ? atm • V2 = constant • T2 = 5oC + 273 = 278 K P1V1 = P2V2 substitute 2.18 atm = ? atm T1 T2 305 K 278 K P2 = 1.987 atm What law best illustrates what happened to the tires in this problem?

  33. 14.2 The Gas Laws Applying the Combined Gas Law • A sample of nitrogen monoxide has a volume of 72.6 mL at a temperature of 16°C and a pressure of 104.1 kPa. • What volume will the sample occupy at 24°C and 99.3 kPa?

  34. 14.3 The Ideal Gas Law Ideal Gas Law • Ideal gases are theoretical • Real gases behave like ideal gases at STP • The ideal gas law relates pressure, temperature, volume, and number of moles • The equation includes universal gas constant R, which “corrects” conditions to STP • Where… • P = pressure in atm • V = volume in L • n = number of particles in moles • R = universal gas constant • T = temperature in K 0.0821 L · atm mol · K

  35. 14.3 The Ideal Gas Law Ideal Gas Law • Example: Tyler is scuba diving along a coral reef. His 10 liter air tank contains 2 moles of oxygen gas at 20oC. What is the pressure of his oxygen tank? • P = ? atm • V = 10 L • n = 2 moles • R = 0.0821 L · atm mol · K • T = 20oC + 273 = 293 K • PV = nRT ? atm * 10 L = 2 mol * 0.0821 L · atm * 293 K mol · K P = 4.811 atm

  36. 14.3 The Ideal Gas Law Applying the Ideal Gas Law • What pressure in atmospheres will 18.6 mol of methane exert when it is compressed in a 12.00-L tank at a temperature of 45°C? • Determine the molar mass of an unknown gas if a sample has a mass of 0.290 g and occupies a volume of 148 mL at 13°C and a pressure of 107.0 atm.

  37. End of Unit 10 Be Prepared for Unit 10 Test on Feb 25th.

More Related