C3 - quantitative chemistry

• Relative formula mass (Mr) - sum of all the relative atomic masses (Ar) of the atoms in the molecular forces
• Percentage mass of an element in a compound = (( Ar × number of atoms in element) ÷ Mr of the compound) × 100
• Balanced equation - a symbol equation with the same number of atoms of each element on each side.
• One mole - 6.02 × 10²³ (Avogardo's constant). Mass in grams of one mole of atoms of an element = Ar of the element, but in a compound = the Mr of the compound.
• Number of moles (mol) = mass in g ÷ Mr
• Conservation of mass - no mass is created or destroyed in a chemical reaction, so the total masses of reactants and products are also the same.
• • Decrease in mass - a gas is made during the reaction and espaces the vessel so it's mass can no longer be accounted for.
  • Increase in mass - a gas from the air is a reactant, so it's mass is added in the vessel.
• Concentration - amount of a substance dissolved in a certain volume of solution.

  • Increase the amount of solute and the concentration increases.
  • Increase the amount of solvent and the concentration decreases.
• Concentration (g/dm³) = mass of solute ÷ volume of solvent
• Limiting reactant - a reactant that gets completely used up in a reaction so limits the amount of product formed. All the other reactants are in excess.
• Work out mass of product:

  write a balanced equation for reaction -> divide the mass of the limiting reactant by the Mr, to find number of moles -> use the balanced equation to find number of moles -> multiply this number of moles by the Mr of the product to find the mass