C3 Quantitative Chemistry

• What are isotopes?

  Different versions of an atom
• What do isotopes of lithium have in common?

  Same number of protons and electrons
• What is the difference between isotopes of lithium?

  Number of neutrons and mass number
• What is relative atomic mass (Ar)?

  Average mass of atom considering isotopes
• What is relative formula mass (Mr)?

  Mass of the molecule from all atoms
• How is relative formula mass (Mr) calculated?

  Add relative atomic mass of each atom
• How do you calculate the percentage mass of an element in a compound?

  Ar x no. of atoms / Mr x 100
• How do you calculate the number of moles?

  moles = mass / Ar or Mr
• What does the law of conservation of mass state?

  No atoms are lost or made in a reaction
• How is atom economy calculated?

  Mr of product / Sum of Mr of reactants x 100
• what is avogadro's constant?

  6.02 x 10 to the power of 23