Ask questions and get helpful answers.

Cobalt-60 is a strong gamma emitter that has a half-life of 5.26 yr. The cobalt-60 in a radiotherapy unit must be replaced when its radioactivity falls to 75% of the original sample. If an original sample was purchased in October 2005, when will it be necessary to replace the cobalt-60?

i have no idea how to start this question please help!

  1. 👍
  2. 👎
  3. 👁
  4. ℹ️
  5. 🚩
1 answer
  1. after t years, the fraction left is

    so, just solve
    .75 = 2^(-t/5.26)
    t = 2.183 years

    2.183 years = 2 yrs + 2.2 months
    so, it gets tossed in Dec 2007, or Jan 2008 (if it was purchased after Oct. 25)

    1. 👍
    2. 👎
    3. ℹ️
    4. 🚩

Answer this Question

Similar Questions

  1. ChemistryStociometry

    6.0g of cobolt (II) carbonate was added to 40cm3 of hydrochloric acid, concentration 2.0 mol/dm3. Calculate the maximum yield of cobalt (II) choloride-6-water and show that cobalt (II) carbonate was in excess. CoCO3 +2HCl = CoCl2 +CO2 + H2O CoCl2 + 6H2O =

  2. Calculus

    A certain radioactive material is known to decay at a rate proportional to the amount present. A block of this material originally having a mass of 100 grams is observed after 20 years to have a mass of only 80 grams. Find the half-life of this radioactive

  3. science

    Cobalt has a mass number of 59 and an atomic number of 27. A student wants to create a model of a cobalt atom. Which statement about the model is correct?

  4. Science-Experiment-Questions

    I did an experiment on a burning candle, and I need help with some of the questions. Thank you very much in return. Please no websites.--more information would be appreciated, thanks:-) I'll list everything of what we went through. Materials: -1 standard

  5. Chemistry

    Calculate the concentration of the cobalt(II) chloride hexahydrate solution titrated in the fine titration experiment. Show your calculations and provide answer with the appropriate number of significant figures. concentration of AgNO3 solution (mol/L)

  6. Nuclear Chemistry

    The half- life of a positron is very short. it reacts with an electron, and the masses of both are converted to two gamma-ray photons: (0e+1)+ (0e-1)---> 2γ (the 0 in front of e is the mass # and behind it is the atomic #) (γ stands for the photons) This

  7. Gen Chem

    Neptunium-239 has a half-life of 2.35 days. How many days must elapse for a sample of 239-Np to decay to 1.00% of its original quantity? I got: close to 15 days. Is this right? I figured that about 1% of the original quantity would be roughly 6.5 Half

  8. chemistry

    The half-life for the first-order decomposition of is 1.3*10^-5. N2O4--> 2NO2 If N2O4 is introduced into an evacuated flask at a pressure of 17.0 mmHg , how many seconds are required for the pressure of NO2 to reach 1.4mmHg ? i know that the half life

  9. chemistry

    Describe how to prepare 1 L of a 0.5 M solution of cobalt chloride hexahydrate (CoCl2 6H2O). Be sure to identify the labware shown above (flask and a scale), explain your reasoning, and show any calculations.

  10. Calculus

    The rate of decay is proportional to the mass for radioactive material. For a certain radioactive isotope, this rate of decay is given by the differential equation dm/dt = -.022m, where m is the mass of the isotope in mg and t is the time in years. A. If

Still need help?

You can ask a new question or browse existing questions.