I completed the A-Level in one year teaching most of the course to myself, earning an A overall. This is a summary of the textbook chapter with all details you will need for the exam, I found this most useful as it streamlines the information and keeps everything I needed in one place. Comparing ma...
In order for a reaction to take place they must collide Catalysts increase the rate of reaction by providing an
with enough energy to break the bonds and at the correct alternative pathway with a lower activation energy, or they
orientation, therefore lots of collisions don’t lead to a hold the reactants at the correct orientation so that the rate
reaction. of successful collisions will increase.
It won’t change the shape of a maxwell=Boltzmann
Factors affecting the rate of reaction- distribution but the activation energy will move to the left
• increasing temperature, this increases the amount as more particles now have the energy to react.
of kinetic energy the particles so the amount of Catalytic converters reduce the levels of
collisions increases a polluting gas. It’s a honeycomb shape
• Increasing concentration, there’s more particles so that’s coated with platinum/ rhodium.
they’re more likely to collide and so rate increases. The honeycomb shape provides a large
However as the reaction occurs concentration surface area and the catalyst lowers the
decreases so rate will fall activation energy so the rate of reaction
• Pressure, only for gas reactions, same effect as can occur very fast.
increasing concentration 1. Gases form weak bonds with the metal atoms of the
• Increasing surface area, the greater the surface area catalyst, holding them in the right position at the
the more likely the two reactants will collide at the correct orientation for them to react on the surface.
needed site. 2. The products break the bonds and move away from the
• Catalyst, will increases the rate of reaction without surface of the catalyst so more gases can react.
being chemically changed
Catalyst: a protein that will increase the rate of reaction Common Exam questions:
by finding an alternative pathway with a lower
activation energy, without being chemically changed “Define catalyst”
Activation energy: the minimum energy needed to
break the bonds of the reactants and start a reaction “Define activation energy”
Transition state/ activated complex: the part where the
activation energy is reached, some bonds are being “How does a catalyst increase the rate of reaction”
formed others are being broken.
“Explain the effect of temperature, pressure, concentration
on the rate of reaction”
5.2 The maxwell-Boltzmann distribution:
“What would you do to increase this reactions rate?”
Maxwell-Boltzmann graphs show the distribution of
energy in the particles. “Explain the maxwell-Boltzmann distribution, how would
• no particles have 0 energy that change under the effect of temperature/ a catalyst?”
• Mode is at the peak of the curve
• No upper limits
• Average energy is slightly higher than the mode
• You can work out the
activation energy on the
graph, anything to the
right has enough energy
to react
Temperature will change the distribution, moving the
mode to the right. The curve flattens as there is still the
same amount of particles and so the area under the
curve must remain constant.
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