Law of Mass Action , Activation Energy , Reaction Rates and Factors affecting the rates of chemical reactions.

Law of Mass Action      The direction of a reaction can be changed by altering the relative concentrations of the reactants and products. A reaction can be pushed forward by increasing the concentration of the reactants. Likewise, a reaction can be reversed by increasing the concentration of the products. Activation Energy      The conversion of one molecule to another is not abrupt but involves a transition state in which the reactant assumes an intermediate form. The transition state possesses a higher potential energy than either the reactants or products and forms an activation energy barrier.      The difference between the potential energy of either the reactants or products and the potential energy of the transition state is called the activation energy. In other words, for a reaction to go forward or in reverse additional energy is needed beyond the DE associated with the reaction. There is an additional "hump" the reaction needs to surmount. The extra energy required for the activation energy may come from the thermal movement of the molecules. Reaction Rates      The rate of a reaction can be expressed as a change in the concentration of the reactant molecules over time. The rate of biological reactions is important because this rate needs to match the body's needs. Factors affecting the rates of chemical reactions. 1. Reactant and product concentrations.    The rate of a reaction usually refers to the net rate because the reaction is always proceeding in both directions. An increase in the concentration of either the reactants or products will increase the net reaction in the direction that will lessen the concentration. If the concentration of the reactants is increased the net reaction will increase in the forward direction. 2. Temperature.    The rate of a reaction increases with increasing temperature and decreases with decreasing temperature. 3. Height of the Activation Barrier    The rate of a reaction increases as the activation energy barrier decreases.