The half-life of 65Zn is 245 days. After x days, 75\% of original activity remained. The value of x in days is . (Nearest integer) (Given: 3 = 0.4771 and 2 = 0.3010)
Answer
102
Solution
Radioactive decay follows first-order kinetics: t = 2.303k A0A and k = 0.693t1/2 = 2.303 2t1/2
⇒ x = t1/2 (A0/A) 2
Here A0A = 10075 = 43, so 43 = 2 2 - 3 = 0.6020 - 0.4771 = 0.1249
⇒ x = 245 0.12490.3010
= 101.7 days 102 days
Answer: 102