Chemical Kinetics - Result Question 36
36. The half-life period of a radioactive element is 140 days. After 650 days, one gram of the element will reduce to 0.03125 grams
(a) $\dfrac{1}{2} g$
(b) $\dfrac{1}{4} g$
(c) $\dfrac{1}{8} g$
(d) $\dfrac{1}{16} g$
(1986)
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Answer:
Correct Answer: 36. (d)
Solution:
- 560 days $=\dfrac{560}{140}=4$ half-lives.
Amount of reactant remaining after $n$-half-lives
$ =\left(\dfrac{1}{2}\right)^{n} \times \text { initial amount }=\left(\dfrac{1}{2}\right)^{4} \times 1.0 g=\dfrac{1}{16} g $
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