Question

A) 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.

B) If there are 80.0 grams of Neptunium-240 (Np-240), how much Neptunium-240 will remain after 4 hours? The half-life of Neptunium-24 is 1 hour.

Answer 1

[ A ] 6400 years

[ B ] 5 grams

Step-by-step explanation:

Answer 2

a) 6400 years

b) 5 grams

Step-by-step explanation:

a) to get 6400 years, the 40 grams is halved 4 times to get to 2.5g and 4 times 1600 is 6400

b) 80 is halved 4 times and the final result you get is 5 grams

80/2= 40/2= 20/2=10/2=5

each divided by 2 represents 1 hour