Physical Chemistry

Collision theory of Reaction rates

Collision theory of Reaction rates

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 …

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How to determine the order of reaction?

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 …

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Second order reaction

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 …

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Molecular Vibrations : IR spectrum

– 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 …

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Molecularity of a reaction

– 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. …

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Sulphur system – Phase diagram of Sulphur

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) …

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Water system, Phase diagram of Water

Water system, one-component system

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 …

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Polymorphism – Allotropy

Polymorphism - Determination of transtion point

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 …

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Phase diagram – Phase Rule

Phase diagram - Phase Rule

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 …

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Derivation of the phase rule

Derivation of the phase rule

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., …

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Degree of Freedom – phase Rule

Degree of Freedom - phase Rule

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 …

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What is meant by A phase and components?

What is meant by A phase and components

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 …

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Applications of distribution law

Applications of distribution law

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 …

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Le Chatelier’s principle

Le Chatelier’s principle

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 …

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Calculation of Kc from Experimental Information

Calculation of Kc from Experimental Information

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 …

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Equilibrium Constant Expression

Equilibrium Constant Expression

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. …

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Law of Mass action

Law of Mass action

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 …

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