3.4 Kinetics

Rate of reaction = quantity of reactant used or product formed / time taken

The rate of a reaction is a measure of the speedway which reactants are changedinto products

The collision theory states that for a reaction to occur the reacting particles must collide together with enough energy to react. Activation energy is the minimum energy needed for a reaction to occur.

Activation energy is the minimum energy needed for a reaction to occur.

Successful collisions are ones that result in a reaction and they take place when reactant particles collide with the activation energy

• Temperature • Concentration of solution • Pressure of gases • Surface area of solid reactants • Presence of a catalyst

When the concentration of a solution is increased the rate if reaction increases. - This is because there a more particles present in a given volume. - This means there are more successful collisions between particles with energy greater or equal to the activation energy - Resulting in more successful collisions in a given time therefore increasing the rate of reaction

As the pressure of a gas increases the rate of reaction increases - This is because the particles are pushed closer together - The same number of particles occupy a smaller volume - This results in more successful collisions betwee particles in a given time - Therefore increasing the rate of reaction

Increasing the surface area of a solid by breaking it into smaller pieces increases the rate of reaction - This is because there is a greate surface area so there are more particles on the surface exposed to the other reactant - There are more successful collisions between particles in a given time - Therefore ther is a faster rate of reaction

Increasing the temperature increases the rate of reaction - This is because the particles are moving faster so there are more frequent collisions - The particles also have more energy so more of the particles have the activation energy and therefore react when they collide - This means there are more successful collisions between particles in a given time - Therefore increasing the rate of reaction

The rate of reaction increases with the presence of a catalyst - This is because the catalyst provides an alternative pathway of lower activation energy -As a result there are more particles with energy greater than the activation energy -This results in more successful collisions between particles in a given time - Therefore increasing the rate of reaction

A Maxwell-Boltzman distribution curve can be used to explain the effects of change in temperature on the rate of a given reaction. It can also be used to explain the action of a catalyst on the rate of a given reaction.

• the peak value moves to the right • the peak is lower as the curve flattens slightly At the higher temperature the reaction is faster (as shown by the distribution) There are more molecules with energy greater than the activation energy which is shown as a greater area under the curve

It is shown by a greater area under the distribution curve

A heterogeneous catalyst is a catalyst that is in a different physical state to the reactants.

Vanadium oxide is used

Iron

Platinum rhodium

The contact process makes sulfuric acid through the reaction of sulfur dioxide and oxygen

The reaction of nitrogen and hydrogen to make ammonia

It is the reaction of oxygen with ammonia to make nitric acid

Contact process

The haber process