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Chapter 11B Gases

Learn how to calculate gas laws using pressure, temperature, volume, and number of moles. Explore the concepts of the Combined Gas Law and Ideal Gas Law and their applications in relating pressure, volume, temperature, and moles. Includes examples and conversion formulas.

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Chapter 11B Gases

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  1. Chapter 11BGases West Valley High School General Chemistry Mr. Mata

  2. Standard 4e • Students will know how to calculate gas laws using pressure, temperature, volume, and number of moles.

  3. Essential Question • How are the Combined gas law and Ideal gas law used to relate pressure, volume, temperature, and number of moles?

  4. S.C.U.B.A. diving in Catalina • What does S.C.U.B.A. stand for??? • Self Contained Underwater Breathing Apparatus • Where is Mr. Mata in the photo above???

  5. Standard Temperature & Pressure • standard conditions = Reference conditions for gases. • Standard Temp = 273 K or 0oC. • Standard Press =1atm = 760 mm Hg • Together 273 K and 1 atm is called: • Standard Temperature and Pressure (STP)

  6. Combined Gas Law • Boyle’s Law & Charles’ Law may be combined into one formula, the Combined Gas Law: P1V1 = P2V2 T1 T2 • Relates pressure, volume & temperature.

  7. Problem #1 • A Helium balloon has a volume of 3.0 L at 1 atm and 273 K. Calculate its volume at 2 atm and 27oC. • V1 = 3 L V2 = ? • P1 = 1 atm • T1 = 273 K • P2 = 2 atm • T2 = 27 +273 = 300K

  8. Problem #1 (cont’d) P1V1 = P2V2 T1 T2 • V2 = P1V1T2 T1P2 • V2 =(1 atm)(3 L)(300 K) (273 K )(2 atm) • V2 = 1.7 L

  9. Problem #2 • A hydrogen balloon has a temperature of 320 K and a volume of 7.5 L and 3 atm of pressure. Calculate its pressure at 58 C and 10.5 L. • V1 = 7.5 L V2 = 10.5 L • P1 = 3 atm • T1 = 320 K • P2 = ? • T2 = 58 +273 = 331 K

  10. Problem #2 (cont’d) P1V1 = P2V2 T1 T2 • P2 = P1V1T2 T1V2 • P2 =(3 atm)(7.5 L)(331 K) (320 K )(10.5 L) • P2 = 2.2 atm

  11. Standard Molar Volume • The volume of 1 mole of any gas at STP is 22.4 L. • This is called the standard molar volume. • The volume of any gas at STP can be calculated if the number of moles is known: • V = (moles) x 22.4 L

  12. IDEAL GAS LAWPV = nRT • P = PRESSURE (in atm) • V= VOLUME (in L) • n = MOLES OF GAS • R= GAS CONSTANT, 0.0821 L* atm/mol * K • T= TEMPERATURE (in K) • Be consistent with units!

  13. Problem #1 • Calculate the temp of 7.5 g H2 gas if the volume is 52.5 L and pressure is 0.8 atm. • First convert values to proper units: • n = 7.5 g H2 x 1 mol H2 = 3.8 mol H2 2 g H2 • T = ? V = 52.5 L • P = 0.8 atm R = 0.0821 L atm / mol K

  14. Problem #1 (cont’d) • PV = nRT • T = PV nR • T= (0.8 atm)(52.5 L) (3.8 mol)(.0821 L atm/ mol K) • T= 134.6 K

  15. Problem #2 • Calculate the pressure of 60 g NH3 gas if the volume is 40 L and temp is 72 C. • First convert values to proper units: • n = 60 g NH3 x 1 mol NH3 = 3.5 mol NH3 17 g NH3 • T = 72 C + 273 = 345 K V = 40 L • P = ? R = 0.0821 L atm / mol K

  16. Problem #2 (cont’d) • PV =nRT • P = nRT V • P= (3.5 mol)(.0821 L atm/ mol K)(345 K) (40 L) • P= 2.5 atm

  17. Conversion Formulas • K = C + 273 • 760 torr = 1 atm = 760 mm Hg

  18. Chapter 11B SUTW Prompt • Describe how the Combined gas law & Ideal gas law relate pressure, volume, temperature, and moles. • Complete an 8 -10 sentence paragraph using the SUTW paragraph format. Hilight using green, yellow, and pink. • Due Date: Tomorrow (start of class).

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