Rates of reaction

Chemistry sac 2

Three things that must occur in order for a successful reaction to occur

- collide with each other

- collide with sufficient energy to break the bonds

within the reactants

- collide with the correct orientation to break the

bonds within the reactants and so allow the

formation of new product

To measure the rate of a reaction two things can be measured

- the volume of gas produced

- the mass loss (if a gaseous product is formed)

Increased temperature

• E ≥ Ea

• Increased average kinetic energy

A homogeneous system

A system in which all the species are in the same state.

reaction quotient

The reaction quotient, Q, is the concentration ratio at any time

during a reversible reaction, and is equal to K at equilibrium.

Q = [products]coefficient/[reactants]coefficient

Equlibrium

A point in a reaction when the rate of the forward and reverse reactions are equal, and the [products] and [reactants] are constant

Le Chatelier’s Principle (LCP)

If a system at equilibrium is subjected to a change that the system will adjust itself to partially oppose the effect of the change

Adding a catalyst

• Catalysts provide an alternative reaction pathway by lowering the activation energy of the reaction

• Increases the proportion of particles with sufficient energy to overcome the activation energy, increasing the number of successful collisions

Increase Surface area

• Only particles on the surface of a solid reactant can participate in the reaction

• Inc surface area inc number of particles on the surface

• Inc freq collisions and number of successful collision in a given time

Increase Pressure

• Increases number of reactant particles in a given volume

• Inc freq of collision and therefore number of successful collisions in a given time

Increase concentration

• Inc number of reactant particles in a