MEDIUMMCQ SINGLEIChO (Chemistry Olympiad)Physical ChemistryChemical kineticsPrevious Year Questions
The half-life of a substance in a certain enzyme- catalysed reaction is 138 s. The time required for the concentration of the substance to fall from 1.28 mg L– 1 to 0.04 mg L–1 is (AIPMT 2011)
A.414 s
B.552 s
C.690 s✓ Correct
D.276 s
Explanation
Fall of concentration from 1.28 mg L–1 to 0.04 mg L– 1 requires 5 half-lives. Time required = 5 × t1/2 = 5 × 138 = 690 s.