Quantitative Chemistry

• Conservation of mass: In a chemical reaction, atoms are not created or destroyed, just rearranged.

  Total mass before the reaction = Total mass after the reaction
• When a metal forms a metal oxide the mass appears to increase because atoms from gaseous oxygen have been added.
• When an acid reacts with a metal the mass appears to decrease because a gas is produced and escapes.
• Relative formula mass is the sum of the relative atomic masses of each atom in a substance.
• State symbols:

  • (s) solid
  • (l) liquid
  • (g) gas
  • (aq) aqueous or dissolved in water
• A symbol equation is balanced when the number of atoms of each element is the same on both sides.
• A mole is the mass of a substance that contains 6.02 x 10^23 particles.
• The Avogrado constant: 6.02 x 10^23
• Moles = mass/Mr
• mass = moles x Mr
• A limiting reactant is the reactant that is completely used up in a reaction.
• The unit for concentration is g/dm^3
• concentration (g/dm^3) = mass (g) / volume (dm^3)
• volume (dm^3) = mass (g) / concentration (g/dm^3)
• mass (g) = concentration (g/dm^3) x volume (dm^3)
• To go from cm^3 to dm^3 divide by 1000
• If the amount of solute in a solution increases, concentration increases.
• If the amount of water in a solution increases, concentration decreases.