Reactions Rates & Chemical Equilibrium

Heat of reaction

The energy absorbed or released in a chemical reaction.

Exothermic reactions

Reactions that release energy.

Endothermic reactions

Reactions that absorb energy.

Activation energy

The minimum energy needed for a reaction to take place.

Activated complex

The unstable transition state from reactants to products in a chemical reaction.

Reaction rate

Is the change in concentration of reactants or products per unit time.

Collision theory

A model that explains reaction rate as the result of particles colliding with a certain minimum energy.

Positive catalyst

A substance that increases the rate of a chemical reaction without itself undergoing a permanent change.

Reversible reaction

A reaction is reversible when products can be converted back to reactants.

Chemical equilibrium

The stage in a reversible chemical reaction when the rate of the forward reaction equals the rate of the reverse reaction.

Le Chatelier's principle

When the equilibrium in a closed system is disturbed, the system will re-instate a new equilibrium by favouring the reaction that will oppose the disturbance.