Physical Chemistry

The Water system – Under normal conditions the Water system is a three-phase, one-component system. – The three phases involved are liquid water, ice, water vapour. – All these phases can be represented by one chemical entity H2O and hence one component of the system. – The number of phases …

Polymorphism – The occurrence of the same substance in more than one crystalline forms is known as Polymorphism. – Polymorphism phenomenon is shown by both elements and compounds. In the case of elements the term allotropy is often used. – The individual crystalline forms of an element are referred to …

Phase Diagram – A phase diagram is a plot showing the conditions of pressure and temperature under which two or more physical states can exist together in a state of dynamic equilibrium. – The following figure is a typical phase diagram for a one-component system. – The diagram consists of …

Derivation of the phase rule – Here the derivation of the phase rule for one-component system and two-component system are discussed. – Consider a heterogeneous system in equilibrium of C components in which P phases are present. – We have to determine the degrees of freedom of this system i.e., …

Degree of Freedom – The term Degree of Freedom represented by F in the phase Rule equation (F = C – P + 2) is defined as follows : the least number of variable factors (concentration, pressure and temperature) which must be specified so that the remaining variables are fixed …

The Phase Rule statement – The phase Rule is an important generalization dealing with the behaviour of heterogeneous systems. – In general it may be said that with the application of phase rule it is possible to predict qualitatively by means of a diagram the effect of changing pressure, temperature …

Applications of distribution law – There are numerous applications of distribution law in the laboratory as well as in industry. – Here we will discuss some more important ones by way of recapitulation. (1) Solvent Extraction – This is the process used for the separation of organic substances from aqueous …

Henry’s law statement – Henry’s law states: at a constant temperature the solubility of a gas in a liquid is proportional to the pressure of the gas above it. – Henry’s law may be mathematically expressed as C = kP where: C is the solubility (or concentration), k is a …

Introduction to Nernst’s Distribution Law – In this topic Nernst’s Distribution Law wlll be discussed – If we take two immiscible solvents A and B in a beaker, they form separate layers. – When a solute X which is soluble in both solvents is added, it gets distributed or partitioned …

Le Chatelier’s principle – In 1884, the French Chemist Henry Le Chatelier proposed a general principle which applies to all systems in equilibrium. This important principle called the Le Chatelier’s principle may be stated as : when a stress is applied on a system in equilibrium, the system tends to …

Calculation of Kc from Experimental Information – To determine the value of Kc of a reaction, write the balanced equation. Then write the equilibrium constant expression. – Substitute in it the equilibrium concentrations of the reactants and products found experimentally. Thus calculate the value of Kc. Solved problem (1) for …

Equilibrium constant: Equilibrium law – Now we will find the Expression of Equilibrium Constant. – Let us consider a general reaction A + B ↔ C + D – and let [A], [B], [C] and [D] represent the molar concentrations of A, B, C and D at the equilibrium point. …

Law of Mass action – Two Norwegian chemists, Guldberg and Waage, studied experimentally a large number of equilibrium reactions. In 1864, they postulated a generalisation called the Law of Mass action. – Law of Mass action states that : the rate of a chemical reaction is proportional to the active …

Chemical Equilibrium is the state of a reversible reaction when the two opposing reactions occur at the same rate and the concentrations of reactants and products do not change with time. Nature of Chemical Equilibrium : its definition – Let us consider the reaction A + B ↔ C + …

Online MCQ test on First law of thermodynamics – In this topic we offer you, online MCQ test in the fundmental of First law of thermodynamics. – It is a simple test to measure the strength of your knowledge in the basics of understanding the topics of First law of …

Laws of Osmotic Pressure – From a study of the experimental results obtained by Pfeffer, van’t Hoff showed that for dilute solutions : (a) The osmotic pressure of a solution at a given temperature is directly proportional to its concentration. (b) The osmotic pressure of a solution of a given …

Theories of Osmosis – Here we will discuss some theories of osmosis. – Several theories have been advanced to explain the action of a semipermeable membrane. – It is probable that the mechanism depends on the particular type of membrane used and also on the nature of the solute and …

Determination of osmotic pressure – The osmotic pressure of a given solution can be determined experimentally by the methods detailed below. – The apparatus used for the purpose is often referred to as osmometer. (1) Pfeffer’s Method – The apparatus used by Pfeffer (1877) for determination of osmotic pressure is …

Diffusion and Osmosis – Just as a gas can diffuse into vacant space or another gas, a solute can diffuse from a solution into the pure solvent. – If you pour a saturated aqueous solution of potassium permanganate with the help of a thistle funnel into a beaker containing water, …

The subject of Measurement of freezing point Depression will be discused FREEZING POINT DEPRESSION Relation between Depression of Freezing point and Lowering of Vapour-pressure – The vapour pressure of a pure liquid changes with temperature as shown by the curve ABC, in Fig. – There is a sharp break at …