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Explain a general step-wise approach to evaluate the pH of the weak electrolyte. |
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Answer» Solution :Step-1: The species present before dissociation are identified as Bronsted-Lowry acid/base. Step-2: BALANCED equations for all possible reaction. i.e. with a species acting both as acid as well as base are written. Step-3 : The reaction with the higher `K_a` is identified as the primary reaction whilst the other is a subsidiary reaction. Step-4 : Enlist in a TABULAR form the following values for each of the species in the primary reaction. (i) Initial concentration C, (ii) Change in concentration on proceeding to equilibrium in term of (a), degree of ionization. (iii) Equilibrium concentration. Step-5 Substitute equilibrium concentrations into equilibrium CONSTANT equation for principal reaction and solve for `alpha`. Step-6: Calculate the concentration of species in principal reaction. Step-7: Calculate pH = -LOG `[H_3O^+]` . |
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