Question

100 gram sample of an element decays in 12.4 hours and now, its mass is recorded as 25 grams. What is the approximate half-life of this radioactive substance?

• A. 24.8 hours
• B. 3.1 hours
• C. 49.6 hours
• D. 1.6 hours
• E. 6.2 hours

Answer 1

The correct option is E 6.2 hours

In one half life period, the 100 g of element will decay to 50 g. In another half life period, 50 g of element will decay to 25 g.
Thus, two half life periods correspond to 12.4 hours. One half life period will correspond to $\frac{12.4}{2}=6.2$ hours.