6 Rate and Extent of Chemical Changes Flashcards
Mean rate of reaction (reactants)
Quantity of reactant used / Time taken
Mean rate of reaction (products)
Quantity of product formed / Time taken
Measurement of quantity of reactant or product
In grams or in cm3
Units for rate of reaction
g/s or cm3/s (where s is seconds)
Collision theory
The theory that chemical reactions only occur when particles collide with sufficient energy
Factors affecting rate of reaction
Temperature, surface area, pressure, concentration, catalyst
Reason increasing surface area increases rate
More particles are available to collide
Reason increasing concentration increases rate
More concentrated means there are more particles in the same volume
Reason increasing pressure increases rate
Higher pressure means there are more particles in the same volume
What is Activation energy
The amount of energy a particle needs before it will be able to react when it collides with another particle
Reason increasing temperature increases rate
Increases the speed at which particles move therefore more frequent collisions. Increases the number of particles which have the activation energy therefore there are more successful collisions
Catalyst
Something which speeds up the rate of reaction but is not used up in that reaction.
How catalysts speed up rate of reaction
They provide an alternative route for the reaction to take which has a lower activation energy.
Reversible reaction
A reaction which can go from reactants to products but also from products to reactants
Chemical symbol for reversible reaction
⇌
Dynamic equilibrium
The point in a reversible reaction when the forward and reverse reaction are occurring at the same rate.
Change of product and reactant amount at equilibrium
It doesn’t change
Haber process
A reaction to generate ammonia from hydrogen and nitrogen
Reactants for the Haber process
Nitrogen: the air
Why is the Haber process at 450 degrees?
