Chemistry

  • Created by: AOconnor
  • Created on: 14-05-18 18:25
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  • Chemistry
    • Equations
      • Half equations
        • Show what happens to a reactant in a reaction
        • Electrons written as e-
        • Fe ---> Fe(2+) + 2e(-)
      • Ionic equations
        • Used to simplify equations
        • Only show species involved in reaction
          • Spectator ions aren't included
        • AgNO3 + NaCL ---> AgCl + NaNO3
          • Ag(+) + Cl(-) ---> AgCl
      • Species refers to different atoms/molecules/ions involved in reaction
    • Conservation of mass
      • Law states that total mass of products is equal to total mass of reactants
        • No atoms created or destroyed
      • There can be apparent changes of mass
        • This occurs when a reaction happens in a non-closed system and a gas can enter/leave
          • When magnesium burns in air to produce magnesium oxide the mass increases because it combines with the oxygen in the air
    • Amount of substances
      • Mole is a measure of the number of particles contained in a substance
        • One mole contains the same number of particles (Avogadro's constant)
          • 6.02 x 10(23)
        • Mol = mass/Ar
      • Limiting Reactants
        • When a chemical reaction stops it is because one reactant is completely used up
          • This is the limiting reactant
            • The other reactant is said to be in excess
      • Concentration of solutions
        • Concentration = mol/volume
    • Energy Transfers
      • Exothermic
        • Heat energy transferred to surroundings
          • Temperature rise
          • Negative energy change
          • Combustion, oxidation and neutralisation reactions
      • Endothermic
        • Heat energy taken in from surroundings
          • Temperature fall
          • Positive energy change
          • Thermal decomposition reactions
      • Energy changes in reactions
        • In exothermic, the nergy required to break bonds is less than the energy released when new bonds are fromed
          • Excess energy released to surroundings
        • In endothermic, the energy required to break bonds is more than the energy released when new bonds are formed
          • Requires energy so it takes it from the surroundings
        • Catalysts reduce activation energy and make the reaction go faster

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