Answer to Question #146791 in General Chemistry for qwerty

Question

4. Plutonium-239 (produced in breeder reactors has a half-life of 24,100 years. How long will it take for a sample of plutonium-239 to decay to 0.100% of its original value?
5. It takes 35 days for a 512 g sample of element X to decay to a final amount of 4 g. What is the half-life of the element X?
6. The half-life of Oxygen-15 is 2 min. What fraction of a sample of O-15 will remain after 5 half lives?

Answer 1

4.

Plutonium-239

T_½ = 24,100 years

From 100% to 0.100% (change to decimal)

1/.1=10

x 24,100 yrs

= 241,000 years

5.

It takes 35 days for a 512 g sample of element X to decay to a final amount of 4 g.

Therefore half life = ?

512 = 256= 128 =128=64=32=16=8=4

This is equal to 7 halves

Therefore;

7t_½ = 35days

t _½ = 5 days

6.The half-life of Oxygen-15 is 2 min. What fraction of a sample of O-15 will remain after 5 half lives

Therefore halve lifes after 2 mins

100% =50% =12.5%= 6.25%= 3.125%

Therefore;

3.125/100 = 0.3125

0.3215 = 1/32