Chemistry 2b

Chemistry 2b

Rates of Reaction
1. Reaction rate=amount of reactant used up /time
  1. Could measure (at timed intervals)...
    1. Volume of gas formed
    2. Number of bubbles formed
    3. Time of for one reactant to dissolve
2. What effects it?
  1. Temperature
    1. Increases energy and therefore kinetic energy
  2. Concentration
    1. Increase collision freqeuncy
      1. more particles for same volume
  3. surface area
    1. Collisions occur on surfaces
  4. Catalysts
    1. Include transition metals and their compounds
      1. Different in different reactions
    2. Reduce costs in industrial reactions
      1. Molecules absorbed on catalyst surface
3. Reaction types
  1. Exothermic
    1. energy to surroundings
  2. endothermic
    1. energy from surroundings
  3. Reversible= Exothermic one way, endothermic the other
    1. Equilibrium occurs when reactions occur at same rate/both directions
      1. Depends on conditions e.g. temperature
4. Yield
  1. The amount of product obtained in a reaction
    1. Better if:
      1. Exothermic
      2. High pressure
      3. removing products and replenishing reactants
Electrolysis
1. Free ions
  1. metals= positive
    1. move to neg. electrode
      1. Cathode
  2. Non-metals= negative
    1. move to pos. electrode
      1. Anode
  3. When molten, free to move
2. Equations
  1. 1/2 equations
    1. Represent oxidations and reductions
      1. e.g. Sodium chlordie
        Na+ (aq) + e- --> Na (s)
        Reuction, pos/neg charge cancel out
        Na+ gains 1 electron, has no charge
        2Cl-(aq)-->Cl2 (g) + 2e-
        Oxidation, neg/pos charge balanced
        2cl- loses 2 electrons
3. Uses
  1. If the metal in the reaction...
    1. Is less reactive than hydrogen
      1. Metal comes out at cathode
      2. Hydrogen stays in solution
        any metal more reactive than hydrogen can react with an acid
    2. Is more reactive than hydrogen
      1. We get hydrogen!
      2. Metal stays in solution
  2. Sulfate solutions give oxygen at anode
Salts, Acids and Alkalis
1. Bases
  1. metal oxides and hydroxides
  2. React with acids
  3. Make salts
    1. acid+metal=metal salt+hydrogen
    2. acid+ammonia= ammonium slat
    3. acid+soluble/insoluble base=metal salt +water
2. Ammonia forms alkaline solution in water
  1. Would be good fertiliser, except to alkaline
    1. React with acid and get neutral salt- perfect
3. All acids contain hydrogen ions
  1. H+
4. All Alkalis contain Hydroxide ions
  1. OH-
5. In neutralisation reactions...
  1. Hydrogen and hydroxide ions react to make water
  2. They always produce a salt
6. Precipitates
  1. Insoluble salts- can be made as precipitates
  2. Iron impurities
    1. make into insoluble salts to remove from water

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	Created by Alfie Ross over 10 years ago