Physical chemistry deals with the basic principles of physical science involved in chemical systems. It often deals with the macroscopic side of chemical systems; like inter molecular forces, thermodynamic properties, chemical equilibria, reaction kinetics and electrochemical processes.
However modern physical chemistry also deals with the principles of quantum mechanics to help in understanding the chemical phenomena at atomic and molecular level.
On this page you can find links to topics in physical chemistry. You may navigate through the physical chemistry topics given below.
Chemical equilibrium is an important topic in physical chemistry that deals with to what extent a chemical reaction proceeds.
It is observed that, in most of the chemical reactions, the reactants are not completely converted to products. The reaction proceeds to certain extent and reaches a state at which the concentrations of both reactants and products remain constant with time. This state is generally referred to as equilibrium state.
The le Chatelier's principle can be stated as:
When external stress is applied on a system at dynamic equilibrium, the system shifts the position of equilibrium so as to nullify the effect of stress.
Chemical kinetics deals with the rates of chemical reactions i.e., how fast a reaction occurs? It is observed that some reactions occur within a fraction of second, whereas some reactions take years together for completion. This topic is introduced at the level of high school physical chemistry.
Collision theory of rates of reactions was first proposed independently by Max Trautzb and William Lewis to explain the rates of bimolecular reactions occurring in gaseous state.
The rate of a chemical reaction is affected by several factors like:
1) Concentration of reactants
2) Pressure
3) Temperature
4) Catalyst
The differential equation that describes the mathematical dependance of rate of reaction on the concentration terms of the reactants is called rate law or rate expression or rate equation.
Electrochemistry deals with the study of electrochemical processes and their applications which involve:
i) the conversion of electrical energy into chemical energy and
ii) the conversion of chemical energy into electrical energy.
It is possible to carry out a non spontaneous chemical reaction by applying sufficient electrical voltage in an electrochemical cell. In this case, the electrical energy is converted to chemical energy.
You will merging of physics and chemistry.
In 1874, Kohlrausch formulated the law of independent migration of ions based on the experimental data of conductivities of various electrolytes. This law can be stated as follows:
At infinite dilution, the dissociation of the electrolyte is complete and hence each ion makes definite contribution to the equivalent conductivity of the electrolyte irrespective of the nature of other ions associated with it.
Electrolysis involves dissociation (lysis) of an electrolyte by using a direct electric current. In this process, electromotive force is used to carryout a non-spontaneous redox chemical reaction.
The setup used to serve this purpose is known as electrolytic cell.
An upcoming area in physical chemistry - Surface chemistry deals with the study of phenomena that occur at the surfaces or interfaces of substances, like adsorption, heterogeneous catalysis, formation of colloids, corrosion, crystallization, dissolution, electrode processes, chromatography etc. Surface chemistry finds its applications in industry as well as in daily life.
Adsorption is the accumulation or concentration of liquid or gas molecules (adsorbate) over the surface of a solid or a liquid (adsorbent). It is a surface phenomenon.
Adsorbate: The gas or liquid that is accumulated over the surface of a liquid or solid is known as adsorbate.
Adsorbent: The solid or liquid on whose surface, molecules of other substance are adsorbed. Solids, particularly in finely divided state, have large surface area and therefore act as good adsorbents.