CHEMICAL KINETICS Chemical kinetics is related with the speed of chemical reactions and the mechanics of reactions. Here are two basic concepts: Concentration change of a substance in a unit time is called reaction rate and shown as dC/dt. Reaction Mechanism: It is the order of the reactions that go one step to the collective change.

THE FACTORS AFFECTING THE SPEED OF CHEMICAL REACTIONS The Nature of the Reactive Substance In a chemical reaction, the bonds between molecules are broken and new bonds are occured. Rate must be depend to special bondings that newly entering to the reaction. Experimental reaction rate is depended to the bringing together of definite substances in a reaction.

So the rate of reaction varies from substance to substance So the rate of reaction varies from substance to substance. Some reactions are so fast that their speed can not be measured (such as sedimentation reactions and neutralization reactions), and others are so slow that human life can not be enough to measure the speed (such as the combination of oxygen and hydrogen and geological reactions).

Concentration of reactive substances In heterogeneous reactions: It covers more than one phase and the velocity is proportional to their contact surface. For example; the corrosion of iron with oxygen increases as the surface increases. In homogenous reactions: It occurs in single phase and the reaction rate depends on the concentration of the reactive substances.

Reaction rate is described as; nA + mB  Product Reaction rate = k [A]n [B]m k: constant of reaction rate n and m are empirically found exponential expressions. These can be negative or fractional, which indicates the inverse proportion. n + m is called the order and indicates the degree of reaction. Although the reaction rate depends on the concentration, the reaction rate can not be calculated only by looking at the structure of the molecules. The reaction rate is only found experimentally.

Experimentally, there can be a dependence of the rate by determining either the increase in the concentration of the product or the decrease in the concentration of the starting substance. For the rate of the reaction, what has been said so far is always over the initial concentration. However, since the concentrations will change continuously during the reaction, the reaction rate will also change.