Question

HELP ASAPPPP

Answer 1

Answer:

13 years

Explanation:

From;

0.693/t1/2 = 2.303/t log (No/N)

Where;

t1/12 = half-life of Cobalt-60 = 5.3 years

t = time taken = the unknown

No = mass of radioactive material originally present = 5.2 g

N = mass of radioactive material at time t = 0.95 g

Substituting values;

0.693/5.3 = 2.303/t log (5.2/0.95)

0.131 = 2.303/t(0.738)

0.131 = 1.6996/t

t =  1.6996/0.131

t = 12.97 years

t = 13 years(to the nearest whole number)