C3 - Quantitative Chemistry

• What is the symbol for atomic mass?

  Ar
• What is the symbol for relative atomic mass?

  Mr
• How do you find the Mr?

  Add together the relative atomic masses of all the atoms in that compounds molecular formula
• How do you find the percentage mass?

  Ar of the element you're looking for, x number of atoms in that element, divided by the Mr of the compound
• What are moles?

  Moles is the unit we use to measure the amount of chemical we have.
• What is one mole of a substance in numbers?

  6.02 x 10^23 particles
• Why is the mole that specific number?

  Because the mass of that many particles of any substance will be exactly the same number as that substances relative atomic mass, in grams
• What is the equation for moles?

  Moles = mass/Mr
• What should the big numbers in chemical formulas be thought of as?

  ratios
• What is the conservation of mass?

  In a chemical reaction, mass is always conserved, no atoms are created or destroyed.
• How can this concept be seen in real life?

  When balancing equations

  When comparing the relative formula masses of each side of the equation

  When comparing the actual masses of each side
• Why might the masses appear to change in a reaction?

  When the reaction involves a gas, the mass might seem to change, because the gas can come from the air, or float out to the air.
• How can the masses not change when the reaction involves a gas?

  If you do the experiment within a sealed container, the gas would be trapped in the container, so when you measure the reactants mass, it will take into account the gases too.
• What is the limiting reactant?

  The limiting reactant limits how much product can be used
• What is dm cubed?


  Decimeters cubed. It's a measure of volume, and is equal to 1000cm cubed
• What is the equation to work out concentration?


  Concentration = mass/volume