C3 - Chemical Economics

rates of reaction (1)
1. how long it takes for a product to form (react)
  1. fast at the start and slows to the end
2. it can be worked out from the gradient of a graph
  1. slope of gradient = y/x
  2. the limiting reaction is the reaction NOT in excess that gets used by but the end of the reaction
    1. the amount of product formed in a reaction is directly proportional to the amount of the limiting reactant used
      1. reaction occurs when particles collide together. if the number of reacting perticles of one reactant is limited, the number of collisions is limited
rates of reaction (2)
1. the higher the number of collisions that take place, the faster the reaction
  1. it can increase by increasing the concentration: raising the temp or the pressure
    1. particles become more crowded -> more collisions
      1. kinetic energy -> move around more quickly
  2. collision frequency: this describes the number of successful collisions between reacting particles each second
rate of reaction (3)
1. explosions and surface area
  1. combustible powders can cause explosions
    1. breaking up a block into smaller pieces increases the surface area
2. catalysts
  1. a catalysts speeds up a reaction. it doesn't change at the end of a reaction
reacting masses
1. relative formula mass
  1. relative atomic mass(A) in the periodic table, the elements all have two numbers. the bigger one is the relative atomic mass (on top)
  2. relative formula mass(M) is all the relative atomic masses added together
2. conservation of mass: during a reaction there are the same number and types of atoms on each side. becuase of this we say the mass is conserved
percentage yield and atom economy
1. percentage yield = (actual yield/predicted yield) x 100
2. the percentage yield tells you about the overall success of an experiment. it compares what you think you should get with what you actually get
3. industrial processes need a high % yield so that they: -reduce waste of reactants, which is costly and wasteful -reduce their costs
  1. they want a high atom economy to make the process more sustainable by making better use of reactants, conserving raw materials and avoiding need to get ride of waste products
4. atom economy = (M of desired products/sum of M of all products) x 100
5. atom economy is the % of reactants changed to useful products
energy
1. bonds BREAKING is an ENDOTHERMIC process
2. bonds MAKING is an EXOTHERMIC process
3. energy is needed to break reactants into separate atoms
  1. atoms join to form new bonds, releasing energy
    1. if more energy is released then needed, the reaction is exothermic
      1. if more energy is needed then released, the reaction is endothermic
4. energy transferred by a fuel
  1. energy transferred (in J) = mass x specific heat capacity x temp change
  2. energy in a gram of fuel = energy released (in J)/ mass of fuel burnt (in g)
batch or continuous
1. disadvantage
  1. continuous
    1. inefficientif not in constant use
      1. there is a high initial building and set-up costs for the chemical platns
  2. batch
    1. each batch has to be supervised so labour costs rise
      1. time is needed for cleaning if product line if changed
        it is inefficient if product is not used all the time.
2. advantages
  1. continuous
    1. makes large amounts of products 24/7
      1. takes place in large chemical plants with good transport links
        plants are automated so have minimum labour costs, making product cheaper
        less energy to maintain
  2. batch
    1. makes a fix amount
      1. allows batches to be stored until needed
        easy to change production to a different product
        can be sold within a given time ('sell by' date)
allotropes of carbon and nanochemistry
1. allotropes are just different structural forms of the same element in the same physical state

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C3 - Chemical Economics

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