3.1.5: Kinetics Flashcards
What is a rate of reaction and how is it calculated?
how quickly something changes
(reactants -> products)
rate of reaction= (reactants used or product produced)/ time
What is collision theory?
- in order for atoms to bond, they must collide in the correct orientation with sufficient energy (energy to overcome atom repulsion)
- there needs to be enough energy to overcome atom repulsom
- when bonds break, molecules to deform to rearrange atoms
increasing temperature, increases energy (kinetic)
How do you put Relative reaction Rates on a graph?
volume × concentration= where y axis ends
molecule size/ temperature= steepness of the line/ how steep
this is because the larger s.a. of the molecule and higher temperature, the faster the rate of reaction.
What is activation energy?
the minimum energy required for a reaction to take place (Ea)
What’s an endothermic and exothermic reaction?
Exothermic (-△H)- energy is released in making bonds (more energy in reactants than products)
Endothermic (+△H)- energy is absorbed in breaking bonds (less energy in reactants than products)
BENDy MEXican
What do you annotate on an exothermic and endothermic graph?
- reactants
- products
- overall energy change (△H)
- activation energy (Ea)
- transition state
- x= time/ reaction progress
- y= energy
What is the highest point on a endothermic/ exothermic graph?
transition state/ active complex
A+B-C–>A-B+C
- reactions occur as when 2 particles approach and the repulsion between atoms causes an increase in potential energy
- all 3 atoms (A,B and C) join by partial bonds and as bond AB forms, BC breaks and potential energy forms
What is a rate of Reaction?
How quickly a reaction takes place
rate of reaction= reactants used (or product produced)÷ time
What are the different methods to test for rates of reaction?
- collecting gas in a syringe (reduction/ gain oxygen)
- measure change in mass
- pH tracker
- measure concentration change
- measure precipitate formed
÷ time
What factors affect rates of reaction?
- concentration
- pressure
- surface area
- temperature
- catalyst
How does concentration affect a rate of reaction?
- there is more particles in the same volume (or the reactant than the water)
- more frequent collisions
- however, as the reactants get used up in a reaction, the concentration drops slowing down the rate
- this increases the rate of reaction
How does pressure affect a rate of reaction?
gases only
- gas particles are compressed into smaller volume
- more frequent collisions
- this increases the rate of reaction
How does surface area affect a rate of reaction?
- more particles exposed at the surface
- so there’s more space for collision to occur between the reactants
- more frequent successful collisions
- this increases the rate of reaction
How does temperature affect a rate of reaction?
- particles gain more kinetic energy
- particles move faster so there’s more frequent collisions
- collide with more energy to meet Ea (with frequency and speed)
- this increases the rate of reaction
How does the presence of a catalyst affect a rate of reaction?
- creates an alternative reaction pathway
- lowers activation energy
- more particles can react with the same energy (small amount)
- this increases the rate of reaction without getting used up
What is the maxwell-boltzman distribution?
- ## shows how speed/ energies of moving molecules vary at different temperatures
What is the maxwell-boltzman curve?
- no molecules with 0 energy
- few molecules with high energy
- lower temp.- higher curve, towards left, ends earlier approaching asymptope
- area under graph always the same for each curve though diff. temperatures
- as temp. increases, so does probability of molecules that meet Ea
- adding catalyst lowers Ea
x axis- energy E
y axis- fraction particles with energy E
How do you draw a maxwell-boltzman curve?
- increasing temp. makes molecules on average have more kinetic energy and move faster
- so more molecules have energies greater than Ea
- as molecules have more ke, they collide more frequently
- temperature increasing also increases frequency and energy of molecules
- this increases rate of reaction
