Question

How long will it take for 40.0 grams of Radium-226 (Ra-226) to decay to leave a total of 2.5 grams of Ra-226? Ra-226 has a half-life of 1600 years.

Answer 1

Answer:

6400 years

Explanation:

Given that;

N/No =(1/2)^t/t1/2

No = amount of radioactive material originally present

N = amount of radioactive material present at time t

t= time taken for N amount of radioactive material to remain

t1/2 = have life of the radioactive material

2.5/40 = (1/2)^t/1600

1/16 =  (1/2)^t/1600

(1/2)^4 = (1/2)^t/1600

4 = t/1600

t = 4 * 1600

t = 6400 years