question_answer 1)

The pH of 0.005 M codeine (\[{{C}_{18}}{{H}_{21}}N{{O}_{3}}\]) solution is 9.95.Calculate its ionization constant and\[p{{K}_{b}}\].

Answer:

We know, \[pOH\] of weak monoacidic base may be calculated as: \[pOH=-\frac{1}{2}\log (C{{K}_{b}})\] \[14-9.95=-\frac{1}{2}\log (0.005\times {{k}_{b}})\] \[-8.10=\log (0.005\times {{K}_{b}})\] \[7.943\times {{10}^{-9}}=0.005\times {{K}_{b}}\] \[{{K}_{b}}=1.588\times {{10}^{-6}}\approx 1.6\times {{10}^{-6}}\] \[p{{K}_{b}}=-{{\log }_{10}}{{K}_{b}}\] \[=-\log 1.588\times {{10}^{-6}}\] \[=5.799\] \[\rho {{K}_{b}}=5.8\]