Topic 9- Kinetics Flashcards
What equation is used to calculate rate?
rate= change in concentration/time
What is the unit for rate of reaction?
moldm-3s-1
What must particles do in order to react?
collide with sufficient energy (activation energy) and the correct orientation
Do most collisions result in a reaction?
no
What factors affect the rate of reaction?
- temperature
- concentration
- catalyst
- pressure
- surface area
What is the effect of increasing temperature on rate of reaction?
increasing temperature –> increased rate of reaction because… a higher proportion of particles have energy greater than the activation energy –> more collisions per second –> increased rate
What is the effect of increasing the concentration/pressure on rate?
increased conc/pressure= increased rate
there are more particles in a given volume –> more frequent collisions –> increased rate
What are the variables in an experiment that can be monitored to calculate the rate of reaction?
- concentration of reactant or product
- gas volume of products
- mass of substances formed
How to calculate rate from a concentration time graph?
-draw a tangent
-work out gradient of tangent using….
gradient=change in y/change in x
What is a catalyst?
a substance which increases the rate of reaction but isn’t used up in the reaction
How do catalysts work and how do they increase the rate of reaction?
- they provide an alternative reaction pathway, with a lower activation energy
- due to lower activation energy, more particles have energy greater than the activation energy, so more frequent collisions and increased rate
What does homogeneous catalyst mean?
a catalyst that is in the same phase as the reactants
What does heterogeneous catalyst mean?
catalyst used in the reaction is in different phase to the reactants
What are the economic benefits of using a catalyst in industrial reactions?
catalysed reactions can occur at lower temperatures so less fuel needed so fewer fuel emissions
enables use of an alternative process with a higher atom economy so fewer raw materials are needed and less waste products produced
Define activation energy
the minimum energy required for particles to collide for a reaction to occur
Name some important features of a Boltzmann distribution curve
- area under the curve= total number of particles
- area under the curve doesn’t change when conditions alter
- curve starts at the origin
- curve does not touch or cross the energy axis
- only the molecules with energy higher than the activation energy can react
What are the axis in a Boltzmann distribution curve?
x-axis = energy y-axis = fraction of molecules
