Summary for spec points 4.6 Rate and Extent of Chemical Change – 4.7 Organic
Chemistry
4.6 – Rate and Extent of Chemical Change
= quantity of reactant used ÷ time
= quantity of product formed ÷ time
Units: grams or cm^3/s or mol/s
To calculate from a graph:
o Draw a tangent at the point in
time required
o Calculate gradient of the tangent
The steeper the line = the faster the reaction
When slope gradient = 0, reaction stopped
Factors that affect the rate of reaction are:
o Concentration
o Pressure
o Surface area : volume
o Temperature
o Catalysts
Collision theory: chemical reaction can occur only when reacting praticles collide
with each other and with sufficient energy
Activation energy – minimum amount of energy needed for successful reaction
Increasing any of the factors will lead to faster reaction (cuz more collisions)
Iron is used for ammonia
o Platinum and palladium are in car catalyctic converters
o Enzymes catalyse biological reactions
Catalysts speed up the reaction, but are not used up
Catalyst provide an alternative pathway for reaction with lower activation energy
Catalysts reduce costs and use of fossil fuels
Reversible reactions are those where product can form reactants
Direction of reversile reaction can be changed by changing the conditions
The same amount of energy is transferred each way in reverse reactions
If one is exo the other one is endo
In a closed system reverse reactions, it is in equilibrium when both reactions occur at
the same rate
Le chateliers principle: by changing the conditions at equilibrium the system will
produce a counteracting change to be at equilibrium again:
o If more reactants are added – more product will be formed to meet the
equilibrium
o If the temperature of a system at equilibrium is increased:
the relative amount of products at equilibrium increases for an
endothermic reaction
the relative amount of products at equilibrium decreases for an
exothermic reaction
o If the temperature of a system at equilibrium is decreased:
Chemistry
4.6 – Rate and Extent of Chemical Change
= quantity of reactant used ÷ time
= quantity of product formed ÷ time
Units: grams or cm^3/s or mol/s
To calculate from a graph:
o Draw a tangent at the point in
time required
o Calculate gradient of the tangent
The steeper the line = the faster the reaction
When slope gradient = 0, reaction stopped
Factors that affect the rate of reaction are:
o Concentration
o Pressure
o Surface area : volume
o Temperature
o Catalysts
Collision theory: chemical reaction can occur only when reacting praticles collide
with each other and with sufficient energy
Activation energy – minimum amount of energy needed for successful reaction
Increasing any of the factors will lead to faster reaction (cuz more collisions)
Iron is used for ammonia
o Platinum and palladium are in car catalyctic converters
o Enzymes catalyse biological reactions
Catalysts speed up the reaction, but are not used up
Catalyst provide an alternative pathway for reaction with lower activation energy
Catalysts reduce costs and use of fossil fuels
Reversible reactions are those where product can form reactants
Direction of reversile reaction can be changed by changing the conditions
The same amount of energy is transferred each way in reverse reactions
If one is exo the other one is endo
In a closed system reverse reactions, it is in equilibrium when both reactions occur at
the same rate
Le chateliers principle: by changing the conditions at equilibrium the system will
produce a counteracting change to be at equilibrium again:
o If more reactants are added – more product will be formed to meet the
equilibrium
o If the temperature of a system at equilibrium is increased:
the relative amount of products at equilibrium increases for an
endothermic reaction
the relative amount of products at equilibrium decreases for an
exothermic reaction
o If the temperature of a system at equilibrium is decreased:
