GASES

• One of the criteria that scientists use to assess the probability of life on other planets is the presence of a habitable atmosphere
• The Earth's atmosphere is one in a million (if not billion), that's why we're able to live on what we call the blue planet
• Atmosphere


  The layers of gases that surround any planet in general
• The composition of the Earth's troposphere (lowermost layer of the atmosphere) is most suitable for supporting life
• Ideal gas


  A gas that satisfies the following conditions:

  1. The gas particles have negligible volume

  2. The gas particles are equally sized and do not interact with neighboring gas particles

  3. The gas moves in a random motion

  4. Collisions between gas particles are perfectly elastic
• It is almost impossible to have an ideal (or perfect) gas, but we can "force" the gas to behave ideally under low-pressure and high-temperature conditions
• Boyle's Law


  At a constant temperature, the pressure of a fixed amount of gas is inversely proportional to the volume of the gas
• Pushing the syringe further

  Decreases the volume occupied by the gas, which results in an increased pressure exerted by the gas towards the plunger
• Charles's and Gay-Lussac's Law

  The volume of a fixed amount of gas maintained at constant pressure is directly proportional to the absolute temperature of the gas
• When working with temperatures in gas laws, the temperature must be on the Kelvin scale
• As the temperature increases

  The kinetic energy of gas molecules increases, which causes the gas to exert more pressure against the container
• Keeping the volume occupied by the gas constant and letting the expanding gas exert more pressure on its container leads to the alternative form of Charles's law, which some references call Gay-Lussac's or Amonton's law
• Kelvin scale


  Absolute temperature scale where 0 K is the lowest possible temperature
• Converting temperatures in ℃ to Kelvin

  T (in K) = T (in ℃) + 273
• This animation demonstrating Charles's law by NASA's Glenn Research Center is in the public domain
• As temperature increases


  Kinetic energy of gas molecules increases, causing the gas to exert more pressure against the container
• Pressure is constant


  Increase in pressure applied by the gas is manifested as an increase in the volume occupied by the gas
• Alternative form of Charles's law (Gay-Lussac's or Amonton's law)

  P1/T1 = P2/T2
• CHARLEP


  Mnemonic to remember Charles' Law, constant Pressure
• Avogadro's law


  At constant temperature and pressure, the volume of a gas is directly proportional to the number of moles of gas present
• Avogadro's law equation


  V1/n1 = V2/n2
• Ideal gases are like clothes - if you increase the amount of gas under constant temperature and pressure, the gas tends to increase its volume
• Avogadro's law is named after Italian chemist Lorenzo Romano Amedeo Carlo Avogadro
• Combined gas law


  P1V1/T1 = P2V2/T2
• The combined gas law was obtained by combining Boyle's law, Charles' law, and Amonton's law
• Gas is compressed to half of its original volume

  Ratio of final temperature over final volume = (P2/P1)*(V1/V2)
• Ideal gas equation


  PV = nRT
• A mole of ideal gases, regardless of identity, occupies a molar volume of 22.414 L at 273.15 K (0 ℃) with a pressure of 1 atm (standard temperature and pressure, STP)
• At standard ambient temperature and pressure (SATP), the temperature is 298.15 K (25 ℃), and the pressure is 1 bar
• Determining volume of 0.67 mol SF6 (146 g/mol) at SATP


  V = (nRT)/P