\(K\,\, = \,\,\frac{{2.303\,\, \times \,\,3\,\, \times \,\,0.3010}}{{40}}\,\, = \,\,\frac{{0.693\,\, \times \,\,3}}{{40}}\)
\({t_{1/2}}\, = \,\,\frac{{0.693}}{K}\,\, = \,\,\frac{{40}}{3}\,\min \,\, = \,\,13\,\,\min \,\,20\,\,\sec .\)
આપેલ : $\log 2=0.3010,\log 3=0.4771,\log 5=0.6989$