3.2.2 reaction rates
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describe the effect of concentration/pressure on rate of reaction
at higher concentrations/pressures there are more particles per unit volume and so the particles collide with a greater frequency and there will be a higher frequency of effective collisions
describe the effect of temperature on rate of reaction
at higher temperatures the energy of the particles increases and they collide more frequently and more often with energy greater than the activation energy
explain how catalysts speed up rate of reaction
catalysts lower Ea by providing a different pathway so more particles have energy above the Ea so more successful collisions occur
what goes on the vertical and horizontal axis for an maxwell boltzmann distribution diagram
vertical- number of molecules with a given energy horizontal- energy
explain increases temperature in a maxwell boltzmann distribution diagram
causes a significantly larger proportion of particles to have energy greater than Ea so frequency of successful collisions increases
how can you calculate reaction rates in a conc vs time graph
• draw a tangent to work out initial rate - (rate) gradient=change in y / change in x
heterogenous catalyst
different state from reactants usually solids whereas reactants are (aq) or (g), reaction occurs at surface of the catalyst
homogenous catalyst
same state as reactants, reaction happens through an intermediate species
describe benefits of catalysts
• speeds up rate of reaction • lower temperatures and pressures can be used to save cost • reduced energy demand -fewer CO2 emissions • enables better atom economy so there is less waste, undesired products and hazardous products