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Gas Law Notes: Formulas

Gas Law Notes: Formulas. Avogadro’s Principle Boyles Law Charles Law Dalton’s Law of Partial Pressures. Avogadro’s Principle. At equal temps and equal pressures, equal volumes of gases contain the same number of particles (atoms, molecules, ions)

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Gas Law Notes: Formulas

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  1. Gas Law Notes: Formulas Avogadro’s Principle Boyles Law Charles Law Dalton’s Law of Partial Pressures

  2. Avogadro’s Principle • At equal temps and equal pressures, equal volumes of gases contain the same number of particles (atoms, molecules, ions) In 1 mole it would be 6.02 x 1023 particles • If V1 = V2, then n1 = n2 (T & P constant)

  3. Avogadro’s Principle • The number of gas particles in a container determines the volume at constant temperature and pressure. The volume is proportional to the number of moles present (V = kn) • mathematically: V1 / n1 = V2 / n2 • This is true for all gases at STP. • 1 mole of any gas will occupy 22.4 L at STP

  4. Pressure: collision of particles with their container. • Pressure exerted by a gas is related to: • # of particles in a set volume • volume • The average kinetic energy (temperature) • A change in either # of particles, volume or temperature will result in a change in the pressure

  5. Boyle’s Law: • If temperature and number of moles of a gas is constant, the pressure exerted by a gas varies inversely with volume. • P is proportional to 1/V (PV = k) • Mathematically stated P1V1=P2V2

  6. Boyle’s Law original pressure x original volume = 2nd pressure x 2nd volume • Example problem: A volume of 273cm3 is at 59.4 kPa pressure, what is the volume at Standard Pressure? P1V1=P2V2

  7. Boyle’s Law Problems • 273cm3 =V1 V2 = ? • P1 = 59.4 kPa • P2 = 101.3 kPa P1V1=P2V2 P1V1 /P2 = V2 =(59.4 kPa) 273cm3 101.3 kPa V2 = 160. cm3

  8. Boyle’s Law Problems • A 3.0 L balloon @ 3atm pressure is returned to STP, find the new volume. P1V1=P2V2 • (3.0atm)(3.0L) = (1.0atm) V2 • (3.0atm)(3.0L)= V2 (1.0atm) V2 = 9.0L

  9. Charles’ Law • Charles found that beginning at 0° Celsius, gas volumes double if raised by 273° Celsius or… for each 1 degree increase, the gas volume increased by 1/273 of its volume at 0 Celsius. • Volume is directly proportional to temperature (V = kT) • Stated mathematically Charles’ Law is: V1/T1 = V2/T2

  10. Charles’ Law Problems • A 2.50 L gas filled flexible container is at room temperature(298K), what volume will the substance occupy if the temperature is increased to 373K? V1/T1 = V2/T2 2.50L/298K = V2/373K V2 (298K)= (2.50)(373K) • V2= 3.13 L

  11. Charles’ Law Problems • A 100mL container is at 250K, what must the new temperature be if the volume is expanded to 600mL? V1/T1 = V2/T2 100mL/250K=600mL/T2 T2 = (250K)(600mL)/100mL T2 = 1500K

  12. Dalton’s Law of Partial Pressures • The total pressure in a container is the sum of the partial pressures of the gases in a container. • …or each gas exerts pressure independently & together they make up the pressure of the container.

  13. Dalton’s Law of Partial Pressures • Doubling the number of particles (while temperature and volume is unchanged) will double the number of collisions. • How does this affect pressure? Pressure doubles!!!

  14. Dalton’s Law of Partial Pressures Ptotal = Pgas1 + Pgas2 + Pgas3 …... • The volume of a gas collected over water must be corrected for the vapor pressure of water. Ptotal = Pwater+ Pgas

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