3.1.5 Kinetics Flashcards
What is needed in order for a reaction to be successful? (2)
There must be enough energy in the collision
The reactants must be moving in the right direction
What is activation energy?
The minimum amount of energy required by particles in order to react
How does energy change as a reaction progresses? (3)
At first, bonds in the reactants stretch
Then, particles have enough energy to break bonds (endothermic)
As particles reform into products, they give out energy (exothermic)
Features of a Maxwell-Boltzmann distribution graph (5)
The curve begins at (0,0) because no molecules have zero energy
The peak of the curve represents the most likely energy of any single molecule
The mean energy is to the right of the peak
The area under the graph represents the number of molecules
The area to the right of Ea represents the number of molecules with sufficient energy to react
The effect of changing temperature on a Maxwell-Boltzmann distribution graph (3)
As temperature increases, the peak lowers and moves to the right as the most likely and mean energy of particles has increased
The area to the right of the Ea increases because more particles have higher energy
The area under the graph stays the same because temperature has no effect on the number of particles
The effect of a catalyst on a Maxwell-Boltzmann distribution graph
Adding a catalyst lowers the activation energy, increasing the area under the graph beyond the Ea so more particles have enough energy to react
The effect of changing concentration on a Maxwell-Boltzmann distribution graph (2)
At higher concentrations, the peak is directly above the initial peak as temperature is constant but there are more particles with the most likely energy
The area under the graph past the Ea increases because more particles have more energy
What is the effect of increasing temperature by 10K?
It doubles the rate of reaction
What is reaction rate?
The change in the amount of reactant or product over time
What is the effect of temperature on reaction rate? (2)
On average, as temperature increases, more reactant particles will have more energy
This means more particles have the activation energy for the reaction, increasing the frequency of successful collisions
What is the effect of concentration/pressure on reaction rate? (2)
Increasing concentration/pressure means there are more molecules of reactant to collide
This causes more frequent collisions so rate of reaction increases
What is the effect of surface area on reaction rate? (2)
A larger surface area exposes more particles to the other reactants
This means collisions are more frequent so reaction rate increases
What is the effect of a catalyst on reaction rate? (2)
A pathway of lower energy is provided to the reactants
This causes more frequent, successful collisions so reaction rate increases
What is a catalyst?
A substance that increases the rate of a chemical reaction without being used up or changed in the reaction
How do catalysts work?
They provide an alternative reaction route of lower activation energy
