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GAS LAWS!

GAS LAWS!. By: Michael Ferraiolo Chemistry Period 3 Miss Lee. Kinetic Molecular Theory of Gases (A Model). A “model” is an approximation that attempts to explain observable behavior, allows for future predictions in experimentation.

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GAS LAWS!

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  1. GAS LAWS! By: Michael Ferraiolo Chemistry Period 3 Miss Lee

  2. Kinetic Molecular Theory of Gases (A Model) • A “model” is an approximation that attempts to explain observable behavior, allows for future predictions in experimentation. • Based on behavior of individual gas particles: (atoms: Ne,He ; molecules H2,Cl2,CO2)

  3. Kinetic Molecular Theory of Gases (A Model) Continued • 4 Postulates 1. The volume of individual particles is assumed to be negligible (zero). 2. The Particles are at great distances from each other – between them, empty space. 3. The particles are assumed to exert no forces on each other, nor do they attract or repel each other.

  4. Kinetic Molecular Theory of Gases (A Model) Continued 4. The average KE of a “collection” of gas particles is assumed to be directly proportional to Kelvin. • ***This model works only for ideal gases*** • Real Gases do have volume, they take up space, and they do exert forces on each other b/t them (melting/boiling) • We use Ideal gases + their behaviors in Chem. 1

  5. TEMPERATURE • The Kelvin Scale: - An index of gas motion - NOT a measurement of heat 2. T, temperature is directly proportional to KE, kinetic energy, energy in motion. - heat a gas sample T ^, KE ^, motion ^

  6. TEMPERATURE CONTINUED - “absolute zero” – 0K – all motion stops - a gas sample at 100K has half the KE of a gas sample at 200K - K = Degrees Celsius + 273 - 273K is standard temperature

  7. Pressure • Individual gas particles exert a force on the side of their containers (balloon). • Atmospheric Pressure: Gravity pulling particles • Atmospheric pressure can change with altitude, greater elevation, less pressure, less gas molecules

  8. Real Gases vs. Ideal Gases Continued • Kinetic Theory works for IDEAL gas behavior – theoretical for almost all situations of T + P • Remember! T – in Kelvin, measure of KE of gas particles

  9. Real Gases vs. Ideal Gases • Remember… Kinetic theory asserts 2 assumptions about gas particles. 1. Gases have no volume, REAL gases do, they are matter therefore they take up some space, though very little. 2. No attractive forces exist b/t gas molecules, but REAL gases do have them, otherwise how could they take condense back to the liquid state.

  10. 3) Units of Pressure – standard conditions 1 ATM = 760 mmHg = 760 torr = 101.3 KPa • ATM= atmospheres • mmHg= millimeters of mercury • Torr= Torricelli's • KPa= kilo Pascal's Ex: convert 9.23 atmospheres of pressure to KPa 9.23 atm x 101.3 KPa = 9.35 x 102 KPa 1 atm Ex: 99.2 KPa to mmHg 99.2 KPa x 760 mmHg = 744 mmHg 101.3 KPa

  11. Dalton’s Law of Partial Pressures • Dalton’s Law of Partial Pressures - PTotal = P1 + P2 + P3 + …. + P8 at a constant T and V The total pressure exerted by a mixture of gases is the sum of the partial pressure of each gas.

  12. .… example • Air is a mix of gas. The partial pressures are: PN2= 593.4mmHg, PCO2= 0.3mmHg, Pothers= 7.1mmHg, oxygen is also a component. Calculate partial pressure of oxygen at a barometric pressure of 1 atm.

  13. Boyle’s Law for Pressure • Boyle’s Law for Pressure – P1V1=P2V2 Constant Temperature, an inverse relationship b/t P + V, as P increases V decreases and vice versa.

  14. Boyle’s Law • P1V1 = P2V2 Example) A 153 cm3 sample of N2 gas originally at a P of 82.34 KPa will occupy what volume at standard pressure?

  15. Charles Law for Temperature • Charles Law for Temperature – Volume Changes V1 = V2 T1 T2 Constant P, a direct relationship b/t V + T, as V increases, T must also increase and vice versa. T in Kelvin (can’t have a negative volume or motion)

  16. Charles’ Law V1 = V 2 T1 T2 Example) A balloon has a volume of 98 cm3 on a 32 C day. If the temperature the following day is 48C, what is the volume?

  17. Guy-Lussac’s Law for Pressure • Guy-Lussac’s Law for Pressure – Temperature Changes P1 = P2 T1 T2 Constant V, a direct relationship b/t P + T , as one increases/decreases so does the other

  18. Combined Gas Law • Combined Gas Law: P1V1 = P2V2 T1 T2 Ideal Gas Law • Ideal Gas Law: PV=nRT or gRT/FM

  19. Combined Gas Law • P1V1 = P2V2 T1 T2 Ex) A sample of diborane gas, B2H6, a substance that bursts into flame when exposed to air, has a P of 345 torr at a T of -15C and a V of 3.48 L. If conditions are change such that the T is 36C and the P is 0.616 atm, what will be the V?

  20. The Ideal Gas Law • PV=nRT n=# of moles How many moles of Argon gas can be found in a cylindrical light tube with a volume of 3.7 L and a under a pressure of 162 KPa. The T in the tube is 350 K.

  21. Ideal gases with mass of gas and FM • PV= g (R)(T) FM Ex) How many grams of carbon dioxide are in your lungs at a T of 37C and under a pressure of 768 mmHg. Your lung capacity is 4.8 L.

  22. …including density • PFM = g = d RT V Ex) Calculate the density of NO2 at 300K if its under a P of 6 atm in a 5.0 L container.

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