Chapter 14 - Kinetics Flashcards
Factors that affect reaction rate
Physical state of reactants
Concentration of reactants
Temperature
Presence of catalyst
Kinetics
Study the rate at which a chemical process occurs and sheds light on the reaction mechanism
Physical state of reactants
To react molecules must come in contact with each other (the more homogenous the faster)
Concentration of reactants
As concentration increases the likelihood of molecules colliding increases
Temperature
Higher the temp the more kinetic energy which means molecules moving faster and colliding more an with more energy
Presence of catalyst
Catalysts will speed up rxns by changing the mechanism of the rxn but catalysts are not consumed during rxn
Temperature and rate
Generally as temperature increases so does rxn rate because K is temperature dependent
The collision model
In a chemical rxn bonds are broken and new bonds are formed
Molecules can only react if they collide with each other
Molecules must collide with correct orientation and with enough energy to cause bond breakage and formation
Activation energy
There is minimum amount of energy required for rxn
Reaction coordinate diagram
Helps visualize energy changes throughout a process (activated complex at peak)
Reaction mechanisms
Sequence of events that describes the rxn
Rxns may occur all at once of through several discrete steps
Each step or whole process is called elementary reaction or elementary process
Catalysts
Increase the rate of reaction by decreasing activation energy by changing the mechanisms
One way it can work is speeding up a rxn by holding the reactants together and helping bonds to break
Enzymes
Catalysts in biological systems
Fits into active sit (lock and key)
Reactions over time
Slow down so instantaneous rate at beginning is best
Rate of appearance and disappearance
Follow mile ratio rules when 1:1
If not aA is (1/a)A/t
