Question

The nuclide As-76 has a half-life of 26.0 hours. If a sample of As-76 weighs 344 g, what mass of As-76 remains after 6.00 days? Hint: calculate k first.

Answer 1

remember all the radio active disintegrate reactions forllow th efirst order kinitics

calaculate teh rate constant first

k = 0.693 / t1/2

k = 0.693 / 26.0 hrs = 0.0266 hrs-1

now use the

rate constant and concentration related equation

k = 2.303 / t log(A0/A]

where

t = time = 6.0 days convert in to hrs

11 day = 24 hrs

6 days = 6 x 24 = 144 hrs

A0 = intial concentration = 344 g

A = concentration after 6 days we have to calculate

0.0266 hrs-1 = 2.303 / 144 hrs log(344 /A)

log(344 /A) = 0.0266 hrs-1/ 0.016 hrs-1 = 1.6625

(344 g /A) = 10^1.6625 = 45.97

A = 344 g / 45.97

A = 7.48 g