Science

posted by Lynette

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?
Begin amount is 1.0
elapsed time is 90y half life 30 years
n=9/30 n=3
90/2^2
90/8 = 11.25mg
thinking it's wrong not sure what I missed.

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?

I tried it this way 112/28= 4 half lives then 2.5/3 1.25
1.25/2=0.625
06.25/2= 0.3125
0.3125/2=0.15625 gram

which is the correct way to do these problems. Am I doing that the correct way

  1. Chris

    1. 30 years= 3 1/2 lives so
    1.0mg ->30yrs-> 0.5mg
    0.5mg->30yrs->0.25mg
    0.25mg->30yrs->0.125mg

    2. correct

Respond to this Question

First Name

Your Answer

Similar Questions

  1. half-life

    If 250mg of a radioactive element decays to 200mg in 48 hours, find the half-life of the element. ln(N o /N) = kt N o =250 mg N = 200 mg t = 48 hours. Solve for k, then put k into the following equation and solve for t 1/2 . k = 0.693/t …
  2. chemistry

    If there are 80 milligrams of a radioactive element decays to 10 milligrams in 30 minutes then what is the elements half life in minutes?
  3. Physics HELP HELP

    (for some reason I keep getting this wrong. I put 90 for c, 5.6 for h and 22 for M(x), Then I took the natural log of both sides, but I keep getting it wrong) The mass of a radioactive element at time x is given by the equation below, …
  4. math

    An unknown radioactive element decays into non-radioactive substances. In 100 days the radioactivity of a sample decreases by 64 percent. a)(a) What is the half-life of the element?
  5. Chemistry

    Assuming an element's half-life is 3.6 years. How much of 2 grams of the element would remain after 10.8 years?
  6. Chemistry

    Calculate the time in which the activity of an element is reduced to 90% of its original value. The half-life period of the element is 1.4*10^10 years . Answer :- 2.13*10^9 years
  7. College algerba

    The​ half-life of a certain radioactive element is about 1500 years. After 2800 ​years, what percentage P of a sample of this element​ remains?
  8. PRe calc story problem!!

    A radioactive element decays exponentially according to the function Q(t) = Q0ekt .If 100 mg of the element decays to 25 mg in 12 days, find the half-life of the element.
  9. pre calc

    A radioactive element decays exponentially according to the function Q(t) = Q0ekt .If 100 mg of the element decays to 25 mg in 12 days, find the half-life of the element. please help
  10. math

    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?

More Similar Questions