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In a layman's term, a base is the opposite of an acid. In other words, a base is everything an acid is not. Recall that in the Part I of this series, we looked at the definition of an acid using three different concepts. Similarly, we are going to define a base using the same concepts. Definition Lewis Bases According to G. N. Lewis, a base is any species that can readily donate a pair of electrons. The availability of lone pair(s) of electrons increases a substance's ability to behave as a base. Examples include H2Ö, ÑH3, Cl-, F- etc. They are also considered to be nucleophiles. Any species with an electron-rich centre is said to be a nucleophile. Brønsted-Lowry Bases According to Brønsted and Lowry, an acid is a proton donor, while a base is a proton acceptor. In other words, any substance that has the ability to accept a proton (hydrogen ion, H+) by donating a pair of electrons to it, is said to be a base. Examples are H2Ö, ÑH3, Br- etc. H2Ö(l) + H+(aq) <----&

Introduction Growing up, we used to think that any substance that burns is an acid, until we learnt about acids, bases and salts in our foundational chemistry class. It was then clear to us that there is more to acids than corrosivity, and not every substance that is corrosive, is an acid. Definition The definitions of an acid is based on three different concepts of acid-base reactions, namely the Lewis, Brønsted-Lowry and Arrhenius concepts. Lewis Acids According to G. N. Lewis, in acid-base reactions, the reactants undergo co-ordinate covalent bonding, in which one reacting species has the ability to accept a lone pair of electrons, while the other can readily donate a lone pair of electrons. A Lewis acid is an electron pair acceptor, because it has an empty orbital. Examples are H+, H3O+, Cu2+, Fe3+. Brønsted -Lowry Acids According to J. H. Brønsted and M. Lowry, an acid-base reaction involves the transfer of proton from one of the reactants to the other. A Brønsted-Low

Half-life of a Reaction The half-life, t1/2, of a reaction is the amount of time it will take the concentration, [A], of a reactant to reduce to half its initial concentration, [Ao]. That is to say,               @ t1/2, [A] = [Ao]/2 ...……(i) The half-life of the various orders of reaction can be calculated by substituting the above equation into the respective integrated rate laws. ( a) Half-life of a Zeroth-Order Reaction Recall that the zeroth-order integrated rate law is given by:                  [A] = [Ao] - kt …………(ii)                  [Ao] - [A] = kt @ t1/2, [A] = [Ao]/2                  kt1/2 = [Ao] - ([Ao]/2)                  kt1/2 = (2[Ao] - [Ao])/2                  kt1/2 = [Ao]/2                    t1 /2 = [ Ao ]/2k …………(iii) Equation (iii) above, gives the half-life for a zeroth-order reaction, which can be obtained by finding the product of half the initial reactant concentration and the reciprocal of the reaction rate constant ([Ao]/2 × 1/k). (b) H alf-