Industrial Processes

Collision Theory

For a chemical reaction to take place, effective collisions must occur; the particles must collide to break bonds and form new ones and these particles must collide with correct orientation. Enough energy must be produced to overcome the activation energy; the energy produced must be greater than the activation energy.

Effective Collisions

When the particles collide with enough kinetic energy to overcome the activation energy and with the correct orientation to break the bonds between particles so new bonds can form.

Activation Energy

The minimum amount of energy needed for a reaction to happen.

Exothermic

releases energy in the form of heat to surroundings

Endothermic

absorbs energy in the form of heat from surroundings

Rate of Reaction

how much product is formed over time

Collisions and Rate

The more frequently effective collisions occur, the faster the rate of reaction.

Factors affecting Rate of Reaction

Concentration, surface area, temperature, pressure, and catalyst.

Concentration (R of R)

When the concentration increases, there is an increase in chance of effective collisions because there are more reactant particles present. It has no effect on kinetic energy.

Surface Area [solids only] (R of R)

When the surface area is increased, then there is a greater space for the reaction to take place; there is an increase in the number of exposed particles that are available for collision to occur, because of this, there is an increased chance of effective collision.

Temperature (R of R)

When the temperature increases, the heat will cause the particles to move faster, which will increase their kinetic energy; they will move faster and will thereby be able to collide more often. The particles will have more KE, which results there being more particles having energy that is greater than or equal to the activation energy, increasing the amount of particles which can collide, increasing the frequency of effective collisions.

Pressure [gases only] (R of R)

When the pressure is increased, there is an increase in particles but a decrease in volume, meaning that there is a higher concentration of particles; more particles per unit of volume. This increases the chance of effective collisions.

Catalysts (R of R)

Catalysts provide an alternative pathway with lower activation energy for the reaction to occur. Because the activation energy is decreased, there will be more particles with energy that is greater than or equal to the activation energy, and therefore there are more particles with enough energy for effective collisions.

Reversible Reaction (⇌)

A reaction where the reactants change into the products and simultaneously the products convert back into the reactants.

Reversible Reaction Conditions

It must be in a closed system; where the transfer of matter is not possible, only the transfer of energy.

Le Chatelier’s Principle

In a reversible chemical reaction, when the equilibrium is disturbed by conditions changing, the system counteracts the change by shifting the position of equilibrium to re-establish the equilibrium.

Dynamic Equilibrium

A system is at dynamic equilibrium when the rate forward = rate reverse and the concentration of the reactants and products are constant. The conditions are that is must be in a closed system and it must be a reversible reaction.

Concentration (Position of Equilibrium)

If the concentration of A is increased then the system will work to remove this by pushing the equilibrium to the other side.

Pressure [gases only] (Position of Equilibrium)

If the pressure is increased, then the volume is decreased, this shifts the equilibrium to the side with the least number of moles. If the pressure is decreased, then the volume is increased, this shifts the equilibrium to the side with the greater number of moles.

Temperature (Equilibrium)

If the temperature is increased, then the endothermic reaction is favoured. If the temperature is decreased, then the exothermic reaction is favoured. If ΔH is positive, then the forward reaction is endo and the reverse reaction is exo. If ΔH is negative, then the reverse reaction is endo and the forward reaction is exo.

ΔH < 0 (-)

If the temperature is increased, then the equilibrium shifts to the left, since the endothermic reaction is favoured, and that is the reverse reaction. If the temperature is decreased, then the equilibrium shifts to the right, since the exothermic reaction is favoured, and that is the forward reaction.

ΔH > 0 (+)

If the temperature is increased, then the equilibrium shifts to the right since the endothermic reaction is favoured, and that is the forward reaction. If the temperature is decreased, then the equilibrium shifts to the left, since the exothermic reaction is favoured, and that is the reverse reaction.

Catalyst (Equilibrium)

The catalyst provides and alternate pathway with lower activation energy for the reaction. The presence of a catalyst has no effect on the position of equilibrium.