Chemical kinetics

Rate of reaction

Main article: reaction rate

Chemical kinetics deals with the experimental determination of catalysts are present in the reaction.

Factors affecting reaction rate

Nature of the Reactants

Depending upon what substances are reacting, the time varies. Acid reactions, the formation of salts, and ion exchange are fast reactions.When covalent bond formation takes place between the molecules and when large molecules are formed, the reactions tend to be very slow.

Physical State

The physical state (On water reactions are the exception to the rule that homogeneous reactions take place faster than heterogeneous reactions.

Concentration

collision theory of chemical reactions, this is because molecules must collide in order to react together. As the concentration of the reactants increases, the frequency of the molecules colliding increases, striking each other faster by being in closer contact at any given point in time. Imagine two reactants being in a closed container. All the molecules contained within are colliding constantly. By increasing the amount of one or more of the reactants you cause these collisions to happen more often, increasing the reaction rate (Figure 1.1)..

Temperature

refrigerator slows down the speed of the rate of reaction since it cools the molecules. On the other hand, an oven gives heat (energy) to the molecules which in turn speeds up the rate of reaction, cooking the food faster.

A reaction's kinetics can also be studied with a temperature jump approach. This involves using a sharp rise in temperature and observing the relaxation rate of an equilibrium process.

Catalysts

A rate of enzyme mediated reactions.

In certain organic molecules specific substituents can have an influence on reaction rate in neighbouring group participation.

Agitating or mixing a solution will also accelerate the rate of a chemical reaction, as this gives the particles greater kinetic energy, increasing the number of collisions between reactants and therefore the possibility of successful collisions.

Increasing the pressure in a gaseous reaction will increase the number of collisions between reactants, increasing the rate of reaction. This is because the activity of a gas is directly proportional to the partial pressure of the gas. This is similar to the effect of increasing the concentration of a solution.

Equilibria

While chemical kinetics is concerned with the rate of a chemical reaction, Belousov-Zhabotinsky reaction demonstrate that component concentrations can oscillate for a long time before finally reaching equilibrium.

Free energy

In general terms, the Free-energy relationships.

The isotopes.

Chemical kinetics provides information on molar mass distribution in polymer chemistry.

Applications

Reaction kinetics provides chemists with the tools to determine and describe the factors important in food decomposition, the hardening of dental materials, the reproduction of micro-organisms, the speed at which stratospheric ozone is destroyed, and how the enzymes influence chemical processes in biological systems.

See also

• Collision theory
• Arrhenius equation
• Beer's law
• Chemical reaction
• Rate law

References

• Preparing for the Chemistry AP Exam. Upper Saddle River, New Jersey: Pearson Education, 2004. 131-134. ISBN 0-536-73157-8