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Gas Law Notes Chemistry Semester II

Gas Law Notes Chemistry Semester II. Ideal Gas Law Combined Gas Law And Guy Lussac’s Law. Ideal Gas Equation. The variables of the physical nature of gases: n : the number of particles (moles) P : pressure V : volume T : temperature expressed always in K. Ideal Gas Equation.

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Gas Law Notes Chemistry Semester II

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  1. Gas Law NotesChemistrySemester II Ideal Gas Law Combined Gas Law And Guy Lussac’s Law

  2. Ideal Gas Equation • The variables of the physical nature of gases: • n : the number of particles (moles) • P : pressure • V : volume • T : temperature expressed always in K

  3. Ideal Gas Equation • Charles stated that volume varies directly with temperature • Boyle stated volume varies inversely with pressure • So…combining these notions, we can set pressure times volume as equal to a constant times the temperature, where the constant is the same every time it is calculated. • Mathematically this is shown…

  4. Ideal Gas Law Boyle’s Law pressure times volume = a constant Charles’ Law: volume is proportional to temperature Combining the two yields the ideal gas law Restated Ideal Gas Law: …

  5. Ideal Gas Law nRis a constant, n is the moles and R is the universal gas constant R =8.31 L kPa /mol K

  6. Ideal Gas Law Problem • What is the volume of a container holding 2.00 moles of a substance at 831.67 kPa and 500K?

  7. Problem Set Up • P = 831.67 kPa • V = ? n = 2.00 moles T = 500K R = 8.31 L kPa/moles K • PV = nRT

  8. Problem cont’d • 831.67*V = 2.00*8.31*500 • V = 9.99 L

  9. Combined Gas Law • Lab experiments are rarely at STP, usually mathematical corrections must be made. • Corrections are made by multiplying of the original volume (V1) by 2 ratios (1 for temp. and the other for pressure) • The math derivation looks like this:

  10. Combined Gas Law Or… Since n is the same on both sides of the equation…

  11. Combined Gas Law

  12. Combined Gas Law Problems • A 7.51 m3 volume @ 59.9 kPa and 5 °C should be corrected to STP. What is the new volume? • P1V1 = P2V2 T1 T2

  13. Set Up • V1 = 7.51 m3 • P1 = 59.9 kPa • T1 = 5 °C • P2 = 101.3 kPa • T2 = 0 °C • V2 = ? Find this • Remember convert T to Kelvin! • Now solve it!

  14. Solution • 59.9 * 7.51 = 101.3 * V2 278 273 • 59.9 * 7.51 * 273 = V2 278 * 101.3 • V2 = 4.36 m3

  15. next question… • Another problem: A helium balloon with volume = 410mL is cooled from 27 °C to -27 °C. P is reduced from 110 kPa to 25 kPa. What is the new V of gas @ the lower temp. and pressure?

  16. Set Up • V1 = 410 mL • P1 = 110 kPa • T1 = 27 °C • P2 = 25 kPa • T2 = -27 °C • V2 = ? Find this

  17. Answer • V2 = 1479 mL

  18. Guy Lussac’s Law Guy Lussac’s Law relates pressure and temperature…. To be used when volume and moles are kept constant

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