Question

A 3.255 g sample of technetium-95 is sealed in a container. After 44.2 hours, the amount of technetium-95 remaining is 0.702 g. (a) Calculate the rate constant k for 95Tc. (b) Calculate the half-life t1/2 for 95Tc.

Answer 1

A 3.255 g sample of technetium-95 is sealed in a container. After 44.2 hours, the amount of technetium-95 remaining is 0.702 g. (a) Calculate the rate constant k for 95Tc. (b) Calculate the half-life t1/2 for 95Tc. Radioactive decay is a first-order process, the rate constant (k) is given by the below equation, k=2.303/t x log [A ]/[A] where, t = time in second=44.2 x 60 x 60 sec [AO] = Initial amount = 3.255 g [A] = Final amount after time t= 0.702 g Therefore, k= {2.303/( 44.2 x 60 x 60 )} x log 3.255/ 0.702 sec - 1 = {2.303 / 159120} x log 4.63675 sec - 1 = 1.447 x 10 x 0.666 sec -1 = 0.9637 x 10 sec -1 (ANSWER a) (Half life) t12 = 0.693/k=0.693 / (0.9637 x 10-) sec =0.719 x 10% sec (ANSWER b)