5.3 - Amounts of Gases

• gas laws

  volume of a gas sample depends on:

  temperature

  pressure

  amount of gas in moles
• molar gas volume equation

  volume/number of moles

  = 24dm^3 at RTP
• ideal gas equation

  pV = nRT

  p: pressure (Pa) t: temperature (K) r: gas constant - 8.31 J K-1 mol -1

  v: volume(m³) n: number of moles
• measuring molar masses of gases

  used to use ideal gas equation to find molecular formula:

  inject weighed sample of liquid into syringe heated in an oven

  measure volume, temperature and pressure of vapour

  measurements are converted into SI units and put in ideal gas equation to find number of moles
• avogadro's law

  volume of a gas is directly proportional to the number of moles when pressure and temperature are constant

  under equal temperatures and pressure equal volumes of gases have equal number of moles
• gay-lussac's law

  pressure is directly proportional to temperature
• charles' law

  volume is directly proportional to temperature
• boyle's law

  pressure is inversely proportional to volume
• molar volume

  volume of one mole of at stated conditions

  24dm³ at r.t.p.
• molar volume of gases at standard temperature and pressure

  22.4 dm³
• ideal gas

  gases that obey ideal gas equation
• real gases

  gases that don't obey ideal gas equation
• gases close to behaving like ideal gases

  helium, oxygen, nitrogen, hydrogen

  at room temperature they are well above their boiling points
• gases that deviate from ideal behaviour

  gases that boil only a little below room temperature and can be liquefied by raising the pressure

  ammonia, butane, sulfur dioxide and cabon dioxide
• converting from kelvin to degrees Celsius

  -273
• converting from degrees Celsius to kelvin

  +273
• volume equation

  number of moles × molar volume (dm³)