Chem Topic 3

• What are moles?

  Something used to compare quantities of substances

  1 mole = 6.02 x 10^23 atoms/molecules
• What is Relative formula mass?

  Sum of the relative atomic masses of all the atoms in a formula unit.

  E.g H2O = 12 + (2x16) = 44
• What does the conservation of mass state?

  The total mass of reactants must equal the total mass of products
• What is the formula for moles?

  Number of moles = Mass / relative atomic or formula mass
• What is stoichiometry?

  The ratio of moles of one substance to another in a reaction.
• What is limiting reactants?

  In order for no reactants to be left over, there must be the correct number of moles of both reactants in order to react completely, according to their stoichiometry.
• What happens when a substance is dissolved in water?

  It dissociates into its ions (e.g H+ & Cl-), as does the water into (H+ & OH- ions)
• What can concentration be given in?

  g/dm^3 or mol/dm^3
• How to convert volume of water?

  cm^3 (or ml) divided by 1000 gives dm^3
• What is the formula for concentration?

  Concentration (mol/dm^3) = moles/volume (dm^3)
• What is percentage yield & how can it be calculated?

  What mass of product is made in a reaction in reality, compared to maximum theoretical mass that could be made.

  % yield = total mass of products/total mass of reactants x 100
• What is atom economy & how can it be calculated?

  How much of a desired product can be made in a reaction compared to the total mass of reactants

  Atom economy = RAM of desired product/total RAM of reactants x 100
• How much volume does one mole of any gas take up?

  24dm^3

  
  

  This is true for RTP (room temperature & pressure):

  20 degrees Celsius, 1 atm
• How do we convert from moles of gas to volume?

  moles of gas -> volume (dm^3) we x24

  volume (dm^3) -> moles of gas we /24