C5-Kinetics Flashcards
What does collision theory state?
Collision theory states that for a reaction to occur:
Particles must collide
With sufficient energy
And with the correct orientation
Most collisions do not result in a successful reaction because they do not meet the second and third criteria
What is activation energy?
The activation energy is the minimum amount of energy which the reacting particles require for a successful collision
How does surface area effect rate of reaction?
Higher surface area = higher rate of reaction
Why does surface area effect rate of reaction?
Only the particles on the surface of a solid will collide with particles of the other reactant so if the surface area is increased, more particles will be on the surface and able to collide with particles of the other reactant. This means that there will be more collisions in total and therefore more successful collisions. Surface area can be increased by decreasing the size of the reactant particles. Powders have a very large surface area.
How does concentration effect rate of reaction?
Higher concentration = higher rate of reaction
Why does concentration effect rate of reaction?
If the concentration of a reactant increases.
More particles of that reactant are present (in the same volume).
This leads to more successful collisions between reactant particles in a given period of time
How does pressure effect rate of reaction?
Higher pressure = higher rate of reaction
Why does pressure effect rate of reaction?
If pressure in a gaseous system is increased
the particles are forced closer together (same number of particles in a smaller volume).
This leads to more successful collisions between reactant particles in a given period of time.
This causes the rate of reaction to increase
How does pressure effect rate of reaction?
Higher temperature = higher rate of reaction
Why does pressure effect rate of reaction?
If temperature is increased, the particles gain energy and move faster (heating transfers energy to the chemicals)
Which leads to more frequent and more successful collisions (collisions with energy greater than the activation energy) between reactant particles in a given period of time
At higher temperatures, a higher proportion of the molecules have the activation energy or more. This means that a higher proportion of collisions is successful
How does the presence of a catalyst effect rate of reaction?
A catalyst = higher rate of reaction
Why does a catalyst effect rate of reaction?
A catalyst works by providing an alternative reaction pathway of lower activation energy
By lowering the activation energy, more collisions are successful in a given period of time.
So the rate of the reaction increases
What is the Maxwell-Boltzmann distribution curve?
A Maxwell-Boltzmann distribution curve is a graph that shows the distribution of energies of gaseous molecules (particles) at a certain temperature.
In a sample of a gas, a few particles will have very low energy, a few particles will have a very high energy, but most particles will have energy in between
The graph shows that only a small proportion of molecules in the sample have enough energy for an effective collision and for a chemical reaction to take place
What is the area under the curve in the Maxwell-Boltzmann distribution curve?
The number of particles in the sample
How does a temperature increase effect the Maxwell-Boltzmann distribution curve?
The most probable energy is lower on the Y-axis and shifted to the right. Higher number of particles past activation energy point
