C4 - Quantitative Chemistry

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  • Quantitative Chemistry
    • The Mole
      • the name given to the amount of a substance
      • Avogadro's constant = 6.02 x 10'23
      • Moles =   mass (g) / Mr
      • the mole of an atom or compound is the RAM in grams
    • Limiting Reactants
      • reactants that get used up first and cause the reaction to stop
      • the amount of the product depends on the limiting reactant
      • the mass of a product can be calculated by using the mass of a limiting reactant and the balanced symbol equation
        • 1) write balanced equation
          • 2) work out Mr of the reactant and product you want
            • 3) work out moles
              • 4) use the number of moles to fin the mass
    • Relative Formula Mass
      • Compounds have a relative formula mass (RAM / Mr)
      • It is the sum of all atomic masses of the atoms in the compound
      • %mass of an element in a compound= (At x no atoms in element / Mr of compound ) x100
    • The Mole and Equations
      • moles can be used to calculate the mass in reactions
      • mass=    moles x Mr
      • the big numbers in symbol equation tell you the amount of moles for each reactant and product
        • if there is not a big number then the mole is 1
      • if you have the masses of the reactants and products you can work out the balanced symbol equation
        • 1) mass/RAM for each substance to find moles
          • 2) Mole / smallest mole in reaction
            • 3) make them all whole numbers if any are decimals
              • 4) write out the balanced equation using the whole numbers neatly
    • Conservation of Mass
      • in a closed chemical reaction the mass of the products is equal to the mass of the reactants
      • atoms cannot be created or destroyed
      • this is the reason we balance equations
      • if the mass changes in an open chemical reaction a gas is usually release, causing it to seem like the mass has decreased or increased
    • Concentration of solutions
      • concentration = mass of solute (g) / volume of solvent (dm3)
      • it is a measure of how crowded thing are

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