Point out the correct decreasing order of pKb values of following amines: C2H5NH2, C6H5NHCH3, (C2H5)2NH and C6H5NH2

The lesser the value of pKb, the weaker the base. Electron withdrawing groups like benzene decreases the basicity and increases the pKb of amines and the alkyl groups (electron releasing groups) increases the basicity and decreases the pKb value. So the correct order of pKb is C6H5NH2>C6H5NHCH3>C2H5−NH2>(C2H5)2NH. Hence option C is correct.