Applications of Le-Chateller’s Principle
I. In the Study of Physical Equilibrium (A) Effect of temperature on solubility: Some solids absorb heat while some evolve heat on dissolution. Hence according to this principle solubility of the former class of solids increases with rise of temperature. For example: (i) (ii) With rise of temperature solubility of increases while that of decreases. (B) Effect of pressure on solubility: Since on dissolution of gas volume decreases, hence on increasing...
read moreFactors Influencing Equilibrium Concentration
The effect of temperature, pressure and adding reactants or products are described under the heading of Le Chatelier’s principle. The effect of inert gas addition is described here. E.g. (i) There is no effect of addition of inert gas if (ii) At constant pressure if or (+) ve then on addition of inert gas the concentration of products increases while that of reactants decreases. (iii) At constant volume if or (+) ve then on addition of inert gas there is no change in concentration of the...
read moreEffect of Temperature on Rate of Reaction
The rate of reaction increases with rise of temperature. It is expressed as specific rate constant. In general it is approximately 2 to 3 times for rise of temperature from . Hence the ratio of specific rate constant of reaction at rise of is known as the temperature coefficient. Temperature coefficient For example, the temperature coefficient for the dissociation of HI, Is 1.8 while that for the reaction of methyl iodide with sodium ethoxide is 2.9 : This is due to the fact that only few molecules out of the total...
read morePseudo Unimolecular Reaction
The reactions having molecularity but order of reaction is one are called pseudo unimolecular reactions. E g. (i) Thus order of reaction is one but molecularity of the reaction is two. (ii) Thus order of reaction is one but molecularity of reaction is two. (iii) Thus order of reaction is one but molecularity of reaction is three. Similarly the reactions having molecularity but order of reaction is two are called pseudo bimolecular...
read moreMolecularity of the Reaction
The number of molecules taking part in the reaction as represented by the simple chemical equation is called molecularity of the reaction or It is number of species which undergo collision to result into a chemical reaction. I.e. to convert into products. E.g. In both these reactions molecularity is 2 while the order of the reaction is 1 as the concentration of only in the first case and in the second case is effected. Some more examples of different molecularity of the reactions are given below: (unimolecular) ...
read moreDetermination of order of Reaction
There are at least four different methods to ascertain the order of a reaction. (i) Integration method: This method consists in performing the reaction between required amounts of the reactants. The products formed are analysed from time to time and the concentration of reactant is determined. These values are substituted in equations for various order reactions. E.g. ………(for first order reaction) ……………(For second order reaction) …….(For third order reaction) and the order of reaction is then known by that...
read moreThird Order Reaction
A reaction is said to be of third order if the rate is determined by the variation of three concentration terms. In other words, the minimum number of molecules necessary for the reaction to take place is three. There may be three different cases in third order reaction. (i) All the three species have equal concentrations. (ii) Two species have equal concentrations and one different. (iii) All three species have unequal concentrations. Characteristics of Third Order...
read moreSecond order Reaction
A reaction is said to be the second order if its rate is determined by the variation of two concentration terms or rate of the reaction is proportional to the second power of the concentration of a single substance. In general, the second order reaction may be of two types: 1. When the concentration of the reactants is same, I.e., 2. When the concentration of the reactants is different, I.e., Case I: When both reactants have equal concentration. Case II: When both reactants have different...
read moreZero Order Reaction
Zero Order Reaction If the rate of reaction is independent of the concentration of the reactant then the reaction is called zero order reaction e.g. If ‘a’ is the initial concentration and is the amount decomposed in time ‘t’ then Characteristics of Zero Order Reactions (i) (ii) (iii) Unit of (iv) Examples;...
read moreOrder of Reaction
The order of reaction may be defined as the sum of the powers to which the concentration (or pressure) terms are raised in order to determine the rate of the reaction. Therefore, for first order reaction, the expression for the rate of reaction may be given as: For second order reaction, For third order reaction, All the above terms have usual meaning. It is important to note that order of reaction is an experimental quantity and it may be a fractional quantity...
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