Kinetics Flashcards
What are two definitions for rate of reaction?
- a measure of how fast the reactants are changing into products
- the amount of a reactant used up over time or the amount of product formed over time
How can u measure the rate of reaction if the reaction produces a gas?
- volume of gas at equal time intervals
- loss of mass as gas forms
Collision theory states that for two particles to react:
- they must collide with each other
- they must collide with the activation energy (the minimum energy for a reaction to happen)
- they must collide in correct orientation
Why is the reaction fastest at the start?
- lots of HCl acid particles available for marble chips to collide with
- higher frequency of successful collisions so rate is fastest
What is collision theory?
States for two particles to react:
- they must collide with each other
- they must collide with the activation energy
- they must collide in correct orientation
Why does the reaction slow down?
- hydrochloric acid particles have reacted with marble chips
- less available for collisions
- lower frequency of successful collisions so rate is slower
Why does the reaction end?
- all hcl particles are used up
- none available to collide with chips
- no successful collision
- reaction overt
What are the 4 conditions that effect rate of reaction?
- Surface area
- Concentration
- Temperature
- Adding a catalyst
Why does increasing the surface area of a solid increase the rate of reaction?
- larger area of solid particles are exposed
- increase in frequency of collisions
Why does increasing the concentration of a solution increase the rate of reaction?
- increasing the concentration of a solution means there is an increase of particles in a given volume
- increase in successful collisions
(Same as pressure)
What has the biggest impact on rate?
- increasing the temp
Why does increasing temperature have the greatest effect on rate?
- not only increases frequency of collisions
- energy with which the particles collide
How does increasing yhe temperature increase the rate of a reaction?
- increasing the temp increases the kinetic energy of they particles so they move faster
- many more particles have energy higher than or equal to the activation energy so a higher proportion of collisions are successful
- increase in frequency of successful collisions
What is a catalyst?
- a substacne that increases rate of reaction without being used up
How do catalysts work?
- by providing an alternative reaction pathway with a lower activation energy
- this means many more particles have energy higher than that of the activation energy so higher proportion of collisions are successful
- increase in frequency of successful collisions
What is maxwell-Boltzmann distribution?
- graphical representation of the energy distribution between particles within a system
Describe the axis of the Maxwell-Boltzmann distribution
- energy against number of particles
What does the curve starting at the origin show?
- no particles have 0 energy
Why do some particles have very low energies?
- particles collide with each other which slows them down
What is the peak of the curve?
- most probable energy
What does the point right of the peak of the curve show?
- mean energy of the particles
What is activation energy
- maximum energy required for reaction to happen, only particles with E>Ea react
Why does the curve descend asymptotically to zero?
- Very few particles have high energies
- theoretical maximum is infinity but probability is >0
What is the area under the curve?
- total number of particles
