1) The activity of a radioactive sample is measured as 9750 counts per minute at t = 0 and as 975 counts per minute at t = 5 minutes. The decay constant is approximately A) 0.922 per minute B) 0.691 per minute C) 0.461 per minute D) 0.230 per minute Answer: Option CExplanation:dNdt=KN 9750=KN0 .....(i) 975 = KN .................(ii) Dividing (i) by (ii) NN0=110 K=2.303tlogN0N = 2.3035log10 = 0.4606 = 0.461 per minute
