PMT Defintions

Activation energy

The minimum amount of energy that particles must collide with to react

Catalyst

Increases the rate of reaction by providing a different pathway for the reaction that has a lower activation energy. They are not used up during the reaction.

Collision theory

Chemical reaction can occur only when reacting particles collide with each other and with sufficient energy

Effect of changing concentration on equilibrium

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

Effect of changing pressure on equilibrium

An increase in pressure cause the equilibrium position to shift towards the side with the smaller number of molecules. A decrease in pressure causes the equilibrium position to shift towards the side with the larger number of molecules

Effect of changing temperature on equilibrium

If the temperature of an equilibrium system is increased then the relative amount of products at equilibrium increases for an endothermic reaction and decreases for an exothermic reaction

Effect of concentration on reaction rate

Increasing the concentration of reactants in solution means the reacting particles will be closer together. This means they will collide more often so there will be a higher rate of successful collisions and a faster rate of reaction

Effect of pressure on reaction rate

Increase the pressure of gaseous reactants means the reacting particles will be closer together. This means they will collide more often so there will be a higher rate of successful collisions and a faster rate of reaction

Effect of surface area on reaction rate

Increasing the surface area of the reactants means there are more exposed reacting particles. This means there are more frequent successful collisions so the rate of reaction increases

Effect of temperature on reaction rate

Increasing the temperature means the particles will have more kinetic energy and so will move faster. If the molecules are moving faster they will collide more often and, since they’ve gained kinetic energy, a larger proportion of the particles will have at least the activation energy. For both these reasons the rate of reaction will increase

Equilibrium

When a reversible reaction occurs 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

Le Chateliers Principle

If a reaction at equilibrium is subjected too a change in concentration, temperature of pressure, the position of equilibrium will move to counteract the change

Rate of reaction

The measure of the amount of product formed or reactant used over time. The units of rate of reaction may be given as g/s cm3/s or mol/s

Reversible reaction

Reactions in which the products from the reaction can react together to form the original reactants. The direction of reversible reactions can be changed by changing the conditions