C2 amount of substance

Cards (22)

  • relative atomic mass is the average mass of an atom of an element, relative to 1/12 the mass of a carbon-12 atom
  • relative molecular mass is the average mass of a molecule, relative to 1/12 the mass of a carbon-12 atom
  • relative formula mass is the relative mass of an ionic compound as this does not exist as a molecule
  • the avogadro constant is the number of atoms/particles in one mole of a substance
  • the avogadro constant is 6.022 x 10^23
  • a mole is the amount of substance that contains 6.022*10^23 atoms/particles
  • moles = mass / Mr
  • concentration represents how much solute is dissolved in a known volume of solution, it is measured in moldm^-3
  • concentration = moles / volume
  • the ideal gas equation is pV=nRT
  • in pV=nRT:
    p = pressure in Pa
    V = volume in m^3
    n = number of moles
    R = gas constant, 8.31
    T = temperature in K
  • no gases obey the ideal gas equation exactly, so no real gases are ideal gases
  • the empirical formula is the simplest whole number ratio of atoms of each element in a compound
  • to find empirical formula, draw a table:
    • first row write masses or percentage by mass
    • second row write Mr
    • third row use moles = mass / Mr to write moles
    • fourth row divide by the smallest
    • scale up to get integers
  • the molecular formula is the actual number of atoms of each element in a compound
  • to find the molecular formula, divide the Mr of the compound by the Mr of the empirical formula, then multiply the empirical formula by this value
  • chemical equations need to be balanced before you can use them in calculations
  • rules for balancing equations:
    • do not change any of the formulae
    • only add coefficients, no other numbers
    • coefficient represents number of moles of that substance
    • if the equation is ionic, the charges on each side must also be balanced
  • atom economy = (mass of desired product / total mass of reactants) * 100
  • a high atom economy means less waste is produced, making it more economically viable
  • percentage yield = (experimental yield / theoertical yield) * 100
  • a high percentage yield means less product has been lost throughout the manufacture process