rates of reaction 2.2 Flashcards
define rates of reaction
rate of reaction is the change in concentration of a reactant or product per unit time
what is a catalyst
a substance which speeds up the rate of reaction without being chemically changed at the end
how do catalysts affect the rate of reaction
a catalyst increases the rate of reaction because it provides an alternate pathway with lower activation energy. more particles have energy eqaul to or greater than the activation energy so more frequent successful collisions will occur
how can a catalyst be identified in a reaction
they are chemically unchanged so can be distinguished from the product. they are not involved in the reaction equation as they are not used up
what is collision theory
for a chemical reaction to take place:
- reactant particles must collide with the correct orientation
- reactant particles must have the activation energy
define activation energy
the minimum amount of energy required for a reaction to take place between two particles
how can you calculate rate of reaction
rate of reaction =
amount of reactant used/ product formed
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time (s)
what units could be used for rates of reaction
g/s
cm^3/s
mol/s
what conditions can be changed to increase the rate of reaction
increase temperature
increase pressure (gas)
increase surface area of reactants (solid)
increase concertation of reactants (solution)
a catalyst
light (photosynthesis etc.)
how does temperature affect rate of reaction
increasing temperature increases the rate of reaction because the reactants have more energy so more particles have energy greater than or equal to the activation energy so there will be more successful reactions. collisions also occur more frequently because the particles have more kinetic energy
how does increasing surface area affect the rate of reation
increasing surface area increases the rate of reaction because more recasting particles are exposed so there are more frequent successful collisions
how does concentration affect the rate of reaction
increasing concentration increases the rate of reaction because there are more reacting particles in the same volume. this means more frequent successful collisions occur
how does pressure affect the rate of a gaseous reaction
increasing the pressure of a gaseous reaction increases the rate of reaction because there are more reacting particles un the same volume of gas (or the same number of reacting particles in a smaller volume) so there are more frequent successful collisions
how do you calculate rates (give units)
rates=
change in concentration / time
moldm-3s-1
