Rate of Reaction

Rate of a chemical reaction is how fast reactants are changed into products
On a graph, the line becomes less steep as the reactants are used up
Mean rate of reaction measured in g/s or cm3/s = quantity of reactant or product used in grams or cm3/ time taken in seconds
Factors that affect the rate of a reaction:
Temperature is increased, the particles all move faster, collide more frequently have more energy so more of the collisions to make the reaction happen.
More concentrated means more particles knocking about in the same volume of water.
The pressure of a gas is increased, means the same number of particles occupy a smaller space.
Makes collisions between reactant particles more frequent.
Increased surface area means more surface for particles to react, increasing the rate

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Collision Theory

Catalyst: A substance that speeds up the reaction without being used up and provides an alternative reaction pathway with a lower activation energy
Different catalysts are needed for a different reaction
A catalyst decreases the activation energy, which is the minimum amount of energy required for the reaction to occur.
Catalysts are usually transition metals
Collision theory: Chemical reactions can occur only when reacting particles collide with each other and with sufficient energy.

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The forward reaction will be going at exactly the same rate as the backward one is when a system is at equilibrium.
This means concentrations of reactants and products have reached a balance and won't change.
A closed system, where equilibrium takes place means that none of the reactants and products can escape and nothing else can get in
The equilibrium lies to the left if the concentration of products is greater than that of the reactants.
If the equilibrium lies to the right, the concentration of reactants is greater than that of the products.
If a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction.

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Le Chatelier’s Principle is the idea that if you change the conditions of a reversible reaction at equilibrium, the system will try to counteract that change
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
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.

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If the concentration of a reactant is increased, more products will be formed until equilibrium is reached again.
If the concentration of a product is decreased, more reactants will react until equilibrium is reached again.
For gaseous reactions at equilibrium:
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
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
Changing the pressure only affects equilibriums involving gases.

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