GASES AND THEIR BEHAVIOR

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GASES AND THEIR BEHAVIOR

• Chapter 5

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Properties of Gases

• Only 4 quantities are needed to define the state
  of a gas
• 1). The quantity of the gas, n (in moles)
• 2). The temperature of the gas, T (Kelvin)
• 3). The volume of a gas , V (Liters) 1000mL1L
• 4). The pressure of the gas, P (atmospheres)

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Gas Pressure

• A measure of the force that it exerts on its
  container. Force is the physical quantity that
  interferes with inertia. Gravity is the force
  responsible for weight.
• Force Mass x acceleration, Newtons 2nd law.
• N kg x m/s2
• Pressure Force/unit area N/m2

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• Barometer invented by Evangelista Torricelli in
  1643. Uses the height of a column of mercury to
  measure gas pressure (especially atmospheric)
• 1mmHg 1torr
• 760mmHg 760torr 1atm 101.325kPa
• 101.325kPa 14.7psi (pounds per square inch)

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Practice problems

• 515mmHg in kPa
• 727mmHg into kPa
• 52.5kPa into atm

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Your problems

• 1. 52.5kPa into atm
• 2. 0.729atm into mmHg
• 3. 522torr into kPa
• 4. 1.10atm into psi
• 5. 800mmHg into atm
• 6. 125kPa into torr
• 7. Rank the following pressures in decreasing
  order of magnitude (largest first, smallest
  last) 75kPa, 300torr, 0.60atm and 350mmHg

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Gas Laws The experimental basis

• Boyles law The father of chemistry.
• His law states the volume of a confined gas is
  inversely proportional to the pressure exerted on
  the gas.
• Pressure and volume are inversely proportional
• Temperature is constant
• For a given quantity of a gas at constant
  temperature, the product of pressure and volume
  is a constant.
• P1V1 P2V2

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Example

• A Sample of carbon dioxide with a pressure of
  55mmHg and a volume of 125mL is placed in a new
  flask. The pressure of the gas in the new flask
  is 78mmHg. What is the volume of the new flask?

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Charles law

• If a given quantity of gas is held at a constant
  pressure, then its volume is directly
  proportional to the Absolute temperature. Must
  use Kelvin
• V1T2V2T1

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Avogadros Law

• Avogadros law says that for a gas at constant
  temperature and pressure , the volume is directly
  proportional to the number of moles of gas.
• V1n2V2n1
• V1 Initial volume
• n1 initial number of moles
• V2 final volume
• n2 final number of moles

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• A 5.20L sample at 18C and 2.00 atm pressure
  contains 0.436 moles of a gas. If we add an
  additional 1.27moles of the gas at the same
  temperature and pressure, what will the total
  volume occupied by the gas be.

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• Suppose we have a 12.2L sample containing 0.50mol
  oxygen gas(O2) at a pressure of 1atm and a
  temperature of 25C. If all this 02 were
  converted to ozone at the same temperature and
  pressure, what would be the volume of the ozone?

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• Charless Law
• 1) If I have 45 liters of helium in a balloon at
  250 C and increase the temperature of the balloon
  to 550 C, what will the new volume of the balloon
  be?

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• 3) I have 130 liters of gas in a piston at a
  temperature of 2500 C. If I cool the gas until
  the volume decreases to 85 liters, what will
  temperature of the gas be?

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• 2) Calcium carbonate decomposes at 12000 C to
  form carbon dioxide and calcium oxide. If 25
  liters of carbon dioxide are collected at 12000
  C, what will the volume of this gas be after it
  cools to 250 C?