Physical Chemistry

– In this topic, we will discuss Acid-Base catalysis: definition, Examples and Mechanism. Acid-Base catalysis – A number of homogeneous catalytic reactions are known which are catalysed by acids or bases, or both acids and bases.  These are often referred to as Acid-Base catalysts. – Arrhenius pointed out that acid …

– In this topic, we will discuss the Magnetic Shielding by Electrons Magnetic Shielding by Electrons – Up to now, we have considered the resonance of a naked proton in a magnetic field, but real protons in organic compounds are not naked. – They are surrounded by electrons that partially …

Theories of Catalysis – There are two main theories of catalysis: (1) Intermediate Compound Formation theory. (2) The Adsorption theory. – In general, the Intermediate Compound Formation theory applies to homogeneous catalytic reactions and the Adsorption theory applies to heterogeneous catalytic reactions. The Intermediate Compound Formation Theory – The Intermediate …

– In this topic, we will discuss Autocatalysis, Catalytic poisoning and Negative Catalysis. Catalytic poisoning – Very often a heterogeneous catalyst in rendered ineffective by the presence of small amounts of impurities in the reactants. – A substance which destroys the activity of the catalyst to accelerate a reaction, is …

Introduction to NMR  – Nuclear magnetic resonance spectroscopy (NMR) is the most powerful tool available for organic structure determination. – Like infrared spectroscopy, NMR can be used with a very small sample, and it does not harm the  sample. – The NMR spectrum provides a great deal of information about …

– In this topic, we will discuss general Characteristics of Catalytic Reactions and Promoters. General Characteristics of Catalytic Reactions – Although there are different types of catalytic reactions, the following features or characteristics are common to most of them. (1) A catalyst remains unchanged in mass and chemical composition at …

– In this topic, we will discuss the Catalysis and The types of catalysis : Homogeneous catalysis – Heterogenous catalysis. What is Catalysis? – Berzelius (1836) realised that there are substances which increase the rate of a reaction without themselves being consumed. – He believed that the function of such …

Collision theory of Reaction rates – According to collision theory, a chemical reaction takes place only by collisions between the reacting molecules. However, not all collisions are effective. – Only a small fraction of the collisions produce a reaction. – The two main conditions for a collision between the reacting …

Determination of the order of reaction – There are at least four different methods to determine the order of reaction as follows: Using integrated rate equations Graphical method Using half-life period The Differential method Ostwald’s Isolation method (1) Using integrated rate equations – The reaction under study is performed by …

Second order reaction – Let us take a second order reaction of the type 2A ⎯⎯→ products – Suppose the initial concentration of A is a moles liter–1. – If after time t, x moles of A have reacted, the concentration of A is (a – x). – We know …

First order reaction – Let us consider a first order reaction: A → products – Suppose that at the beginning of the reaction (t = 0), the concentration of A is a moles liter–1. – If after time t, x moles of A have changed, the concentration of A is …

– In this subject we talk about Molecular Vibrations as introduction to understand IR spectrum Molecular Vibrations – Before discussing characteristic infrared absorptions, it’s helpful to understand some theory about the vibrational energies of molecules. – The following drawing shows how a covalent bond between two atoms acts like a …

– we will discuss the Molecularity of a reaction and the Differences Between Order and Molecularity. Molecularity of a reaction – Chemical reactions may be classed into two types : (a) Elementary reactions (b) Complex reactions – An elementary reaction is a simple reaction which occurs in a single step. …

The Sulphur system –  Sulphur system is a one-component, four-phase system. – The four phases are: (a) Two solid polymorphic forms : Rhombic Sulphur (SR) Monoclinic Sulphur (SM) (b) Sulphur Liquid (SL) (c) Sulphur Vapour (SV) – All the four phase can be represented by the only chemical individual (sulphur) …

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 …