Summary Chemistry Notes - Kinetics As AQA - Questions and answers
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Unit 3.1.5 - Kinetics
Instelling
AQA
This documents includes every past paper question I could find for Kinetics As, with the answers. Active recall is really important when studying for exams which these notes really allow you to do. There is also only so many ways they can ask a question in Chemistry.
How to use these notes: Ju...
Explain the process that causes some molecules in this
sample to have very low energies
1. Collisions
2. Cause some particles to slow down
Explain why, even in a fast reaction, a very small percentage
of collisions leads to a reaction.
Only a small percentage of collisions have E >Ea
Other than by changing the temperature, state how the
proportion of successful collisions between molecules can
be increased. Explain why this method causes an increase
in the proportion of successful collisions.
1. Add a catalyst
2. This Lowers Ea
3. More molecules have energy > Ea
Define the term activation energy for a chemical reaction.
The minimum amount of energy required for a reaction to occur
Use these curves to explain why a small decrease in
temperature can lead to a large decrease in the rate of a
reaction
,As there are significantly fewer molecules with energy greater
than the Ea
Give one reason why most collisions between gas-phase
reactants do not lead to a reaction. State and explain two
ways of speeding up a gas-phase reaction other than by
changing the temperature.
1. Molecules do not collide with enough energy
2. Increase the pressure - there are more particles in a given
volume therefore there are more successful collisions in a
given time
3. Add a catalyst - Lowers Ea by providing an alternative
route
At any time, most of the molecules of G have energy less
than the activation energy.
Suggest why, at a constant temperature, most of G
eventually decomposes.
As the molecules gain energy due to collisions
State the effect, if any, of adding a catalyst on the time
required for G to decompose, compared with a similar
sample without a catalyst.
Explain in general terms how the catalyst has this effect.
1. Decreases
2. Lowers Ea by providing an alternative route
In order for two particles to react they must collide. Explain
, why most collisions do not result in a reaction.
As they do not collide with energy greater than the activation
energy
State one way in which the collision frequency between
particles in a gas can be increased without changing the
temperature.
Increase pressure
Suggest why a small increase in temperature can lead to a
large increase in the reaction rate between colliding
particles.
As there are significantly more molecules with energy greater
than the activation energy
Explain in general terms how a catalyst works.
1. Lowers Ea
2. By providing alternative route
The total area under the distribution curve represents
The total number of molecules present
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