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Gases

Gases. Kinetic Molecular Theory. Particles of matter are in constant motion. The state of a substance at room temperature depends on the strength of the intermolecular forces between the particles. 5 assumptions of Kinetic Theory. 1. gases are tiny particles

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Gases

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  1. Gases

  2. Kinetic Molecular Theory • Particles of matter are in constant motion

  3. The state of a substance at room temperature depends on the strength of the intermolecular forces between the particles.

  4. 5 assumptions of Kinetic Theory • 1. gases are tiny particles • 2. particles have elastic collisions with each other • 3. particles in constant motion • 4.no forces between particles • 5. speed of particles determined by temperature

  5. Bonding (Intramolecular) ionic bond- transfer of electrons between cation (+) and anion(-) Subtract electronegativities to predict bond type

  6. Covalent bond- sharing of electrons • Nonpolar- equal sharing of electrons • Polar –unequal sharing of electrons

  7. Polar molecule has a slightly + and – side due to the difference in electronegativities of the elements involved.

  8. Intermolecular forces • Occur between 2 molecules (polar covalent) • 3 major types: 1.dispersion • 2. dipole to dipole 3. hydrogen bond

  9. Dispersion force- temporary and weak strong polar molecule causes a nonpolar molecule to become slightly polar

  10. Dipole to Dipole • slightly + end of one molecule is attracted to the slightly – end of another molecule • Shape can cancel out polarity

  11. Hydrogen bond- attraction between molecules • Uses H,F, O, N. (generally the strongest attraction)

  12. Fluidity, expansion, diffusion occur due to the weak or none attraction between molecules • Which states of matter have these properties?

  13. Which diffuses faster? • High molar mass or low molar mass? • Polar or nonpolar molecules? • High IMF or low IMF?

  14. Ideal gases have NO attraction between molecules • Real gases have some attraction between molecules

  15. A change of state occurs when IMF are formed or broken • Increase in heat? • Decrease in heat?

  16. Changing gases into liquids • Increase pressure • Decrease temperature • This causes increase in IMF

  17. Ideal Gases are gases that follow the Kinetic Molecular theory

  18. Real Gases (all gases) deviate from the KMtheory

  19. Gases behave more ideally when? • what pressure? • what temperature?

  20. 3 categories of gases • Noble gases • Nonpolar gases • Polar gases

  21. Noble Gases • Have an octet • How many valence electrons? • Attract electrons? Why?

  22. Nonpolar gases • nonpolar bonding– equal sharing of electrons • Example– diatomics • List these? • Do these gases form IMF with other molecules? • Why?

  23. Polar Gases • Polar bonding- unequal sharing of electrons • Form IMF with other molecules • Examples- ammonia (NH3) Water vapor

  24. Pressure- force/area • units of pressure- these are equivalent • 1 atmosphere (atm) • 760 torr • 760 mmHg • 101.3 kpascal

  25. Convert 2.25 atm=_______ mmHg 895 mmHg = ______ atm 850 mmHg = _____ torr

  26. Temperature • Temperature must use the kelvin scale • Kelvin scale is based on absolute zero • Particles are motionless

  27. Measure in celsius and convert to kelvin • C + 273 = kelvin • Kelvin – 273 = celsius

  28. STP • Standard temperature 273 kelvin or 0 c • Standard Pressure= 1 atm • STP is used to compare gases and results

  29. Boyles Gas Law • Pressure varies inversely with volume • Pressure increases volume _______ • Volume increases  pressure ______ • Formula P1V1 = P2V2

  30. Charles Gas Law • Volume is directly related to temperature • volume increases temperature _____ • Temperature increases  volume ________ • Formula :

  31. Gay Lussac Gas Law • Pressure is directly related to temperature • Increase in temperature  ____ pressure • Increase in pressure  _______ temperature • Formula:

  32. Combined Gas Law • Takes into consideration all 3 variables (Page 375 in your book) • Formula:

  33. Problem • What is the new volume at STP if the gas that was originally collected at a pressure of 795 mmHg and a temperature of 30 C has a volume of 355 mL?

  34. problem • A gas was collected at 1.65 atm with a volume of 65.0 ml, what is the new volume if the pressure is changed to 2.00 atm? The temperature remains constant.

  35. Dalton’s Law of partial pressures • Total pressure of the gas is equal to the sum of all of the pressures. • PT= P1 + P2 + P3

  36. Collected over Water • PT= Pgas + Pwater • Pgas = Ptotal - Pwater • Water table of the back of Periodic Table • Page 859

  37. Avogadro’s Law • Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules

  38. Standard Molar Volume of a gas at STP is • 22.4 liter/mole regardless of the gas

  39. All collected at STP • 2.67 moles of an unknown gas = ______ liters • 3.56 liters of gas = __________ moles

  40. Molar mass g/mole • A gas has a mass of .953 grams with a volume of 333 mL. What is the molar mass of this gas at STP? (remember must use liters)

  41. .334 grams of an unknown gas has a volume of 250 mL when collected at STP. What is the molar mass of this gas?

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