Question

Given the solution 0.50 M NH₃ (aq) with K_b = 1.75 * 10^-5, calculate the pH using an I.C.E. table

Answer 1

The solution is given below-

The approximation we made is viable only if less than 10% or 15% base is ionized,This criterion is arbitrary one as it applies only if Kb is smaller than about 0.01 C i.e smaller than about when C=0.01M, at C=0.1M and so on.The error introduced under these conditions is less than 5%.So it is quite a good approximation rather than to solve a hectic quadratic equation.