Реферат: Rate Of Reaction In Sodium Thiosulphate And

is called the activation energy, or Ea. The size of this activation energy is

different for different reactions. If the frequency of collisions is increased

the rate of reaction will increase. However the percent of successful

collisions remains the same. An increase in the frequency of collisions can be

achieved by increasing the concentration, pressure, or surface area.

Concentration ? If the concentration of a solution is increased there are more

reactant particles per unit volume. This increases the probability of reactant

particles colliding with each other.

Pressure – If the pressure is increased the particles in the gas are pushed

closer. This increases the concentration and thus the rate of reaction.

Surface Area ? If a solid is powdered then there is a greater surface area

available for a reaction, compared to the same mass of unpowdered solid. Only

particles on the surface of the solid will be able to undergo collisions with

the particles in a solution or gas.The particles in a gas undergo random

collisions in which energy is transferred between the colliding particles. As a

result there will be particles with differing energies. Maxwell-Boltzmann

energy distribution curves show the distribution of the energies of the

particles in a gas.

The main points to note about the curves are:

1. There are no particles with zero energy.

2. The curve does not touch the x-axis at the higher end, because there will

always be some particles with very high energies.

3. The area under the curve is equal to the total number of particles in the

system.

4. The peak of the curve indicates the most probable energy.

The activation energy for a given reaction can be marked on the distribution

curve. Only particles with energy equal or greater than the activation energy

can react when a collision occurs.

Although Maxwell-Boltzmann distribution curves are for the particles in a gas,