Question

HELP ASAP PLZ EARTH SPACE SCIENCE

1. An element has a half-life of 30 years. If 1.0 mg of this element decays over a period of 90 years, how many mg of this element would remain?


2. A 2.5 gram sample of a radioactive element was formed in a 1960 explosion of an atomic bomb at Johnson Island in the Pacific Test Site. The half-life of the radioactive element is 28 years. How much of this element will remain after 112 years?


3. An element has a half-life of 29 hours. If 100 mg of the element decays over a period of 58 hours, how many mg of the element will remain?

Need help asap plz !!

Answer 1

1. 0.125mg.

2. 0.15625

3. 25mg

Step-by-step explanation:

1. In 30 years it will divide in half so in 30 yrs it would be 0.5; 30 years after that (or in 60 years) it would be 0.25; in 30 more or 90 years, it would be 0.125mg. The answer is 0.125mg.

2. 112/28 years = 4 half lives go by.

2.5 /2=1.25

1.25 /2=0.625

0.625 /2=0.3125

0.3125/2=0.15625

0.15625 is the answer

3. 58/29=2 half lives, so:

100/2= 50mg

50/2=25mg

25mg is the answer