Quantitative chemistry

• balanced equation same number of atoms in the reactants & products
• Ar- relative atomic number
• Mr - relative formula mass
• Percentage mass of an element in a compound = Ar X number of that element in the compound / Mr of the compound X 100
• Number of moles for element = mass (g) / At
• Number of moles for compound = mass (g) / Mr
• Avagardos constant - 6.02 x 10 ^23
• the law of conservation of mass

  • no atoms are created or destroyed in a chemical reaction, which means the mass of the reactants = the mass of products
  • a balanced chemical equation obeys this law, showing the same number & types of atoms on both sides
• when masses change

  • if mass increases, it could be due to gas from the air becoming part of the products in an unsealed container
  • If mass decreases, a gas may be formed & escaped from the mixture in a a non - closed system
• limiting reactant

  • in a chemical reaction, you have a excess reactant & limiting reactant
  • The excess reactant is more than you need
  • The limiting reactant is used all the way up before the access reactant
  • Limiting reactant used the excess reactant
  • The amount of product then forms depending on the amount of limiting reactant
• explain how mass of a solute & the boiling of a solution is related to the con of a solution

  • if we increase the mass of a solute & the volume stays the same the concentration of solution increases
  • If we increase the volume & the mass is the same the concentration of the solution decrease