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PIPC Chp 5 Rate of Reaction - Coggle Diagram
PIPC Chp 5 Rate of Reaction
Factors affecting RoR
Temperature
Process
Increased temperature
Molecules have higher energy levels
More molecules have sufficient energy to overcome activation energy of reaction
Increased reaction rate
Catalyst
A catalyst increases the rate of a chemical reaction without itself undergoing a permanent chemical change
Process
Activation energy of the reaction is lowered
When colliding,** more molecules have equal or greater energy to overcome Ea barrier
Increased reaction rate
Concentration
Increased concentration
Increased
number of collisions per second
>Increased reaction rate
Activation energy
The
minimum energy
that molecules have to collide with to
initiate
a chemical reaction
Ea varies between reactions
Rate of reaction is the fastest at the start, but decreases due to decrease of reactants
Expressing rate of reaction
Units: M(Molarity)/s
aA+bB->cC
fraction with reactant is negative, rep. decrease of reactant
fraction with product is positive, rep. appearance of product
Reversible reaction
A reversible reaction is one that can proceed in either direction
Reactants to products or products to reactants
As A and B are used up to form C and D, the forward rate decreases and the reverse rate increases
Dynamic Equilibrium
Forward rate=Reverse rate
Concentrations of reactants and products appear constant
The forward and reverse rates of reaction are called “equilibrium rates”
The concentrations of reactants and products are called “equilibrium concentrations”
Equilibrium constant Kc
If Kc >>1, equilibrium lies to the right (favours formation of products)
If Kc <<1, equilibrium lies to the left (favours formation of reactants)
Kc indicates the extent to which a reaction will proceed
Equilibria Shifts
Le Chatelier’s Principle:
When stress is applied to a chemical system in equilibrium, the equilibrium shifts to relieve the stress
Factors
Concentrations
Add reactant>equilibrium shifts right
Remove reactant>equilibrium shifts left
Pressure
Pressure increase, equilibrium shifts to the side with less gas molecules to release pressure
Pressure decrease, equilbrium shifts to side with more gas molecules to regain lost pressure
Temperature
Temp
increase
, molecules will react to
use up the energy
, shift to
endothermic
reaction
Image: there is available food, so eat up that food first
temp decrease, molecules will react to
generate energy(release energy
), shift to
exothermic
reaction
Image: not enough food, so generate the food already in the stomach
Catalysts
No shift in equilibrium, just affects rate at which equilibrium will be reached
How to answer the question
What is the stress applied
How to relieve this stress
Equilibrium shifts where?
Equilibrium is re-established
