1. Rate and extent of chemical change

    Cards (11)

    • Mean rate of reaction 

      • quanitiy of reactant used OR product formedtime taken\frac{quanitiy\ of\ reac\tan t\ used\ OR\ product\ formed}{time\ taken}
      Rate of reaction - g/s or cm3^3/s
      Reactant / product formed Ready- cm3^3
      Time - s
    • factors affecting the rates of chemical reactions
      • concentration of reactants
      • pressure of reactants
      • surface area of reactants
      • temperature
      • catalyst
    • collision theory
      • chemical reactions can occur only when reacting particles collide with each other and with sufficient energy
    • activation energy
      • minimum amount of energy that particles must have to react
    • Catalysts
      • change the rate of chemical reactions but are not used up
      • increase the rate of reaction by proving a different pathways for the reaction that has a lower activation energy
      • Different reactions need different catalyst
    • Reversible reactions
      • products of the reaction can react to produce the original reactants:
      -A + B \leftrightarrowC+D
      • direction of reversibl reaction a can be changed by changing conditions:
      -Ammonium chloride \leftrightarrowammonia + hydrogen chloride
      (forward reaction heat)
      (Reverse reaction cool)
    • reversible reactions (Endo / EXO)
      • hydrated copper sulfate (blue) \leftrightarrowanhydrous copper sulfate + water (white)
      (Forward reaction is endo)
      (Reverse reaction is exo)
      • if a reversible reaction is exothermic in one direction and endothermic in the opposite direction, the same amount of energy is transferred in each case
    • equilibrium
      • forward and reversible reactions occur at exactly the same rate
      • if any changes is made to any of the conditions, the system counteracts the change
    • changing concentration
      • if concentration of reactants is increased, more products will be formed until equilibrium is reached again
      • if concentration of products decrease, more reactants will react
    • changing temperature
      • if temperature increases , favours endothermic
      • if temperature decreases , favours exothermic
    • changing pressure
      • increase pressure
      -equilibrium shifts to the side with fewer molecules
      • decrease pressure
      -equilibrium positions shift to side with larger number of molecules
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