C6 - The Rate And Extent Of Chemical Change Flashcards
What are the equations for mean rate of reaction?
Mean rate of reaction (g/s) (cm^3/s) =
Quantity of product formed
_______________________________
Time taken
Mean rate of reaction (g/s) (cm^3/s) =
Quantity of reactant used
_____________________________
Time taken
Describe the effect of the concentration of reactants on the rate of a chemical reaction
When the concentration increases, the reactant particles become more crowded. The frequency of collisions between reactant particles increases, causing the rate of reaction to increase.
Describe how the surface area of solid reactants affects the rate of chemical reactions.
If the surface area to volume ratio of a reacting solid is increased:
More reactant particles are exposed at the surface.
The frequency of collisions between the reactant particles increases which increases the rate of reaction.
Describe how the temperature of a chemical reaction affects the rate of chemical reactions.
If the temperature of the reaction mixture is increased:
Reactant particles move more quickly which increases the energy of the particles.
The frequency of successful collisions between reactant particles increase, increasing the rate of reaction.
Define Collision theory.
Chemical reactions can occur only when reacting particles collide with each other and with sufficient energy.
Define activation energy.
The minimum amount of energy that particles must have to react.
How do catalysts increase the rate of reaction?
Catalysts increase the rate of reaction by providing a different pathway for the reaction that has a lower activation energy.
What are the advantages of catalysts?
Catalysts increase the rate of chemical reactions but are not used up during the reaction, so can be reused again and again.
Catalysts are quick without needing to increase the temperature which saves money.
What is meant by a reversible reaction?
The products of the reaction can react to produce the original reactants.
If a reversible reaction is (…) in one direction, it is (…) in the opposite direction.
- (Exothermic)
- (Endothermic)
Define Equilibrium.
When a reversible reaction takes place in apparatus which prevents the escape of reactants and products, equilibrium is reached when the forward and reverse reactions occur at exactly the same rate.
What is the effect of changing conditions on equilibrium?
If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change
What happens if the concentration of a reactant is increased?
More products will be formed until equilibrium is reached again
What happens if the concentration of a product is decreased?
More reactants will react until equilibrium is reached again.
What happens 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.
What happens if the temperature of a system at equilibrium is decreased?
The relative amount of products at equilibrium decreases for an endothermic reaction.
The relative amount of products at equilibrium increases for an exothermic reaction.
What happens if there is an increase in pressure in a reversible reaction?
An increase in pressure causes the equilibrium position to shift towards the side with the smaller number of molecules, as shown by the symbol equation for that reaction.
What happens if there is a decrease in pressure in a reversible reaction?
A decrease in pressure causes the equilibrium position to shift towards the side with the larger number of molecules, as shown by the symbol equation for that reaction.
