moles and volumes

• Standard solution


  A solution of known concentration.
• Concentration

  The amount of solute, in moles, dissolved in 1 dm³ (1000 cm³) of solution
• Molar gas volume, V

  The volume per mole of gas molecules at a stated temperature and pressure
• Mole

  The amount of any substance containing as many elementary particles as there are carbon atoms in exactly 12 g of the carbon-12 isotope, i.e. 6.02 x 10^23 particles
• Avogadro constant N

  6.02 x 10^23 mol-1, the number of atoms per mole of carbon-12
• ideal gas equation

  pV = nRT
• what is R in pV = nRT?

  gas constant
• ideal gas equation units

  • p = pressure (Pa)
  • V = volume (m3)
  • n = moles (mol)
  • R = gas constant
  • T = temperature (K)
• gas constant, R

  8.314
• to convert cm3 to m3 you must multiply by 10^-6
• to convert dm3 to m3 you must multiply by 10^-3
• to convert from celsius to kelvin +273
• kPa to Pa x 1000
• 1 dm3 = 1000 cm3 = 1000 ml = 1 litre
• RTP is 20C and 101kPa (1 atm) pressure
• At RTP 1 mole of gas molecules has a volume of approx 24 dm3 = 24,000 cm3
• Molar gas volume at RTP is 24 dm3 mol-1
• mol = volume/molar gas volume
• when the volume (V) is in dm3, divide volume by 24
• when the volume (V) is in cm3, divide volume by 24,000
• moles (n) = concentration (c) x volume (V)
• You will usually measure volumes in cm3 so you will need to convert into dm3 by dividing by 1000
• To work out the mass concentration (g dm-3) , you need to convert between moles and grams. So do moles x Mr = mass