Chemical Calculations With Mass

• What is conservation of mass?

  In a chemical reaction, atoms are not created or destroyed, just rearranged, so total mass before = total mass after reaction
• When a metal forms a metal oxide, why does the mass increase?

  Atoms from a gaseous oxygen have been added
• When an acid react with a metal, why does the mass decrease?

  A gas is produced and escapes
• What is relative formula mass?

  The sum of the relative atomic masses of each atom in a substance
• What are the four state symbols and what do they stand for?

  (s) solid, (L) liquid, (g) gas, (aq) aqueous or dissolved in water
• How can you tell when a symbol equation is balanced?

  The number of atoms of each element is the same on both sides
• What is a mole?

  Mass of a substance that contains 6.02x1023 particles
• Give the value for Avogardo's constant

  6.02x1023
• Which formula is used to calculate the number of moles from a mass and Mr?

  Moles=Mass÷Mr
• Which formula is used to calculate the mass of a substance from number of moles and Mr?

  Mass=MolesxMr
• What is a limiting reactant?

  The reactant that is completely used up in a chemical reaction
• What is the unit for concentration?

  g/dm3 or mol/dm3
• Which formula is used to calculate concentration from mass and volume?

  Concentration=Mass ÷ Volume
• Which formula is used to calculate volume from concentration and mass?

  Volume=Mass ÷ Concentration
• Which formula is used to calculate mass from concentration and volume?

  Mass=Concentration X Volume
• How can you convert a volume reading in cm to dm

  Divide by 1000
• If the amount of solute in a solution is increased, what happens to its concentration?

  Increases
• If the volume of water in a solution is increased, what happens to its concentration?

  Decreases