Kinetics, Equilibra And Redox Reactions
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Formula for rate of reaction
Rate of reaction= Amount of reactant used or product formed/ time
What are particles in liquids and gases always doing?
Moving and colliding with each other
Do they react every time they collide?
No only when conditions are right
What two things must be true according to collision theory for a reaction to occur?
Collide in the right direction they need to be facing each other in the right way Collide with at least the activation energy required
What’s activation energy?
The minimum amount of kinetic energy that particles need to react
Why is activation energy required to start off a reaction?
Need at least the energy needed to break their bonds and start the reaction
What reactions happen easily?
Ones with low activation energy
What reaction happen don’t happen easily?
Ones with a high activation energy so you need to give particles extra energy by heating them
How much energy do molecules in a gas have?
Some don’t have much kinetic energy and move slowly Others have loads of kinetic energy and whizz along but molecules are sometimes in between
If you plot a graph of number of molecules in a gas with different kinetic energy what do you get?
Maxwell-Boltzmann distribution
Area under Maxwell-Boltzmann distribution?
The total number of molecules
Where does the curve of maxwell-Boltzmann begin?
(0,0) no molecules have zero energy
Peak of curve maxwell-Boltzmann?
Represents most likely energy of any single molecule
Mean (average) energy is where?
All the molecules a bit right to a peak
Which molecules react?
Some molecules have more than the activation energy. These are the only ones that can react
Increasing the temperature of a reaction does what? Maxwell-Boltzmann
The particles will on average have more kinetic energy and move faster
What does a higher temperature mean for the proportion?
Greater proportion of molecules will have at least the activation energy and be able to react Changes shape of maxwell-Boltzmann distribution curve pushing it over to the right
Total number of molecules is the same for?
Each of these reactions meaning the area under the curve must be the same
Why does a slight increase in temperature result in quite a large increase in reaction rate?
Molecules move faster so collide more More molecules have the activation energy required Together can lead to large increase in reaction rate
What does increasing pressure do the rate of reaction?
Increase concentration of reactants in a solution the particles will be on average closer together If closer they will collide more often. If collisions occur more frequently they’ll have jute chance to react meaning increasing concentration increases reaction rate
Pressure does what to the rate of reaction?
If a reaction involved gases, increasing pressure works in just the same way as increasing concentration Raising pressure pushes all gas Particles together making them more likely to collide so collisions take place more frequently and reaction rate increases
What’s a catalyst?
A substance that increases the rate of reaction providing an alternative reaction pathway with a lower activation energy. The catalyst is chemically unchanged at the end of the reaction
Why are catalysts great?
They don’t get used up so you only need a tiny bit of catalyst to catalyse a huge amount of stuff. They do take part in reactions but they’re remade at the end
Why are catalyst fussy about which reactions they catalyse?
They often only work on a single reaction