Beryllium-7 has a half-life of 53 D. A sample was observed for one minute and there were 26,880 decays.
a.) what is the activity level of the sample?
b.) what will the activity level of the sample be after 265 d?
c.) after how many days will be activity level of the sample be 112 Bq?
d.) what was activity level 106 d before the sample was observed?
e.) how many days earlier was activity level 8 times greater than the observed level?

asked by Samaira
  1. a. The rate of decay = 26,880 dpm (decays/min)
    k = 0.693/t1/2
    Solve for k and substitute into the below equation.
    ln(No/N) = kt
    No = 26880
    N = ?
    k from above
    t = 265 days

    1 Bq = 1 dps
    Your sample is 26,880 dpm so
    26,880 decays/min x (1 min/60 sec) = about 448 dps.
    ln(No/N) = kt
    No = 448
    N = 112
    k from above
    Solve for t in days.

    ln(No/N) = kt
    No = ?
    N = 26,880
    k from above
    t = 106

    e. see d.

    posted by DrBob222

Respond to this Question

First Name

Your Answer

Similar Questions

  1. physics

    Suppose 32000 radioactive nuclei are in a sample. About how many remain after two days if the half-life is 22 hrs? What is the initial activity of the sample in decays per minute?
  2. Chemistry - Radioactivity

    The activity of a sample of Ba-137m has decreased by 75% from its initial activity after 5.10 minutes. What is the half-life of Ba-137m? What fraction of activity remains after 6.25 minutes? (A=Aoe (-kt); k = .693/t1/2)
  3. college Geol 101

    Suppose you have a sample of clamshell at a Paleoindian site and you measure the 14C activity of a 100-gram sample of carbon as 320 disintegrations per minute (or 3.2 disintegrations per gram of carbon per minute). a.What was the
  4. college physics part 2

    the activity of a sample of carbon has one-eighth of the initial activity. carbon-14 has a half-life of 5730 yr. how old is the sample in yr?
  5. chemistry

    The half-life for the radioactive decay of calcium-47 is 4.5 days.If a sample has an activity of 4.00uCi after 13.5 days, what was the initial activity of the sample?
  6. Physics

    University students, studying the activity of a particular radioactive isotope which had a half-life of 12.0 hours. If the original activity of the sample was 448 kBq, what would the activity be 3.00 days later?
  7. Ap chemistry

    if a 84g sample of thorium decays with a 10 minute half life, how much would the sample weight in a half hour?
  8. college geology help please

    I was the same person from yesterday. I need help on a question. I don't type very good so I have one of my host family do it for me. so please help us. Suppose you have a sample of clamshell at a Paleoindian site and you measure
  9. physics-Radioactivity

    1) The number of radioactive nuclei in a particular sample decreases over a period of 15 days to one-seventeenth the original number. What is the half-life (in days) of these nuclei? 2) What is the activity of a sample of 14C that
  10. 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? half-life: b)How long will it take for a sample

More Similar Questions