1. CALC -- integrals!

    Iodine-131 is used to treat hypo-thyroidism since it is preferentially absorbed by the thyroid and typically involves a total radiation dosage of 10,000,000 millirem. Iodine-131 has a half-life of eight days. 1. Set up the appropriate integral to represent

    asked by anonymous on February 4, 2008
  2. calculus -- PLEASE HELP!

    Iodine-131 is used to treat hypo-thyroidism since it is preferentially absorbed by the thyroid and typically involves a total radiation dosage of 10,000,000 millirem. Iodine-131 has a half-life of eight days. 1. Set up the appropriate integral to represent

    asked by anonymous on February 5, 2008
  3. Chemistry

    If there is a radiation that has a half life of 10 days and we have it for 110 days, what will be the fraction of radiation left?

    asked by Jennifer on November 6, 2011
  4. chemistry

    If there is a radiation that has a half life of 10 days and we have it for 110 days, what will be the fraction of radiation left?

    asked by g on July 10, 2011
  5. chemistry

    Some radioactive nuclides have very short half-lives, for example, I-31 has a half-life of approximately 8 days. Pu-234, by comparison has a half-life of 24,000 years. Explain why both of these examples are dangerous, even though their half-lives are very

    asked by kenzie on June 7, 2018
  6. physics

    If the physical half-life of sulfur-35 is 87.1 days, and the biologic half-life in the testicle is 632 days, what is its effective half-life in this organ? I know i have to find the time and then the half-life. But im having trouble finding the time

    asked by Sarah on October 24, 2013
  7. half-life

    1. The half-life of a first-order reaction is 9.89 minutes. How many minutes will have elapsed after 27 half-lives? My answer is 267.03. 2. The half-life of a second-order reaction is 2.508 days. How many days will have elapsed after 8 half-lives? My

    asked by Issac on February 7, 2007
  8. Chemistry

    When is an isotope considered stable? _(Select all that apply.)_ The isotope does not emit a form of radiation. The isotope’s half-life is longer than the average human life. The isotope emits some form of radiation. The isotope’s half-life is too long

    asked by Quinn on October 22, 2018
  9. Science - Radiation

    A radioactive isotope, used in the agricultural industry has a half life of 8 days. On application, the radiation is emitted is measured at 12500 counts per sec (cps). If the area that it is applied to cannot be used until the radiation strength is less

    asked by Manu on January 26, 2013
  10. 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

    asked by Sarah H on March 28, 2008
  11. chemistry

    How do you find the half-life of an element? Please explain and show me how to do this. I know the answer is 14.3 days, but I don't know how to work it. thank you! the problem is: After 42 days, a 2.0-g sample of phosphous-32 contains only 0.25g of

    asked by Ryan on December 13, 2007
  12. chemistry

    The disintegration of a radioisotope, such as I-131 to Xe-131, is another example of a first-order reaction. It has a half-life of 8.0 days. I-131 -> Xe-131 + e If you start with 1.40 g I-131, how many grams of I-131 will be left after the following days?

    asked by Ashley on July 1, 2012
  13. physics

    If half life of iodine 131 is 8 days, how much from 32g remain after 40 days (5 half lives).

    asked by henry on August 19, 2016
  14. math

    The half life of the radio active substance is the time require the half the substance to decay. the mount A ( in grams) of 100 gram sample of a radio active substance remaining after t half lives by A equals to 100 (0.5) t. suppose the substance has a

    asked by sai on January 17, 2018
  15. college

    . S-35 (t1/2 = 87.4 d) is used in cancer research. The biological half-life in the human body is 90 days. What is the effective half-life of S-35?

    asked by kurt on May 3, 2010
  16. college chem

    S-35 (t1/2 = 87.4 d) is used in cancer research. The biological half-life in the human body is 90 days. What is the effective half-life of S-35?

    asked by Anonymous on May 3, 2010
  17. Math

    1. Iodine-131 is used to find leaks in water pipes it has a half life of 8.14 days. If 36 days have passed and there is now 2.34g left. What is the initial amount? 2. Sr-85 is used in bone scans and has a half life of 64.9 days. If there is 23 percent of

    asked by Scott on April 19, 2018
  18. Physics

    Gold-198 with a half life of 2.6 days is used to diagnose and treat liver disease. Write a half life decay equation that relates the mass of au-198 remaining to time in days. What percentage of a sample of Au-198 would reamin after 1 day, 1 week? Given the

    asked by AlphaPrimes on March 3, 2016
  19. math

    You have just isolated a new radioactive element. If you can determine its half-life, you will win the Nobel Prize in physics. You purify a sample of 2 grams. One of your colleagues steals half of it, and eight days later you find that 0.1 gram of the

    asked by Roseanne on October 21, 2012
  20. Math with science

    Radioactive iodine treatment is so successful at treating hyperthyroidism that it has virtually replaced thyroid surgery. To the nearest full day, determine how long it will take for 400 millicuries of I-131, which has a half-life of 8 days, to decay to

    asked by Liz on July 27, 2008
  21. Algebra

    Andrew measures the amount of a very unstable substance to be 100 moles. The half-life of this substance is 3 days (after 3 days, half is gone). Write an exponential function that models this situation where y is the amount of substance and x is time in

    asked by Jessica on May 1, 2012
  22. algebra

    Andrew measures they amount of a very unstable substance to be 100 moles. the half life of this substance is 3 days(after 3 days, half is gone). write an exponential function that models this situation where Y is the amount of substance and X is time in

    asked by Anonymous on April 26, 2013
  23. 12th grade Math - word problems

    #1.) The population of bacteria after t hours is given by P(t) = 500/(1+83.33e^-0.162t) a.) What is the initial population? b.) When will the amount of bacteria in the population be 12? #2.) Which investment yields the greater amount after 4 years? a.)

    asked by Jamie on September 20, 2010
  24. Biology

    _____________provided significant sources of energy on early Earth, and were most likely involved in the origin of life. Options A) Volcanic activity, violent thunderstorms, and ultraviolent radiation B) Bombardment from meteorites, gamma radiation, and

    asked by Sabrina on August 29, 2007
  25. chemistry

    Which of the following statements about UV radiation is/are FALSE? (Select all that apply). ? a. UV B radiation covers a longer wavelength spectrum than UV A radiation. b. UV B radiation has sufficient energy to break any covalent bond. c. UV B radiation

    asked by Jasmine on September 21, 2008
  26. science

    A Geiger counter is used to measure the activity of a sample of iodine-131. Based on the data, what is the half-life of iodine-131? A. 16 days B. 8 days C. 4 days D. 12 days

    asked by finley on August 20, 2016
  27. 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? Ok i narrowed it down to either 10 or 30...but im rly confused so if u could help it wuld be grea 80 40 1 min 20 2 min

    asked by jojo on March 4, 2007
  28. Math

    A radioactive material takes 60 days to cut its radiation in half. If it starts at 100%, when will it be at 5%?

    asked by Anonymous on June 19, 2014
  29. science

    a radioisotope, Iodine-131, has a half life of 8.1 days. explain what this means. draw a particle diagram for a sample 12 particles of I-131 initially after 8.1 days and after16.2 days.

    asked by mason on May 24, 2016
  30. Chemistry. Half Life Problem. Help Plz

    If the half-life of iodine-131 is 8 day, how much would remain undecayed after 8 day if we started with 38 grams? How much at 16 days? 24 days? 32 days?

    asked by Dominick on December 8, 2015
  31. half-life of radioisotope

    A radioisotope has a half-life of 4 days. How much of a 20-gram sample of this radioisotope remains at the end of each time period? 1) 4 days 2) 8 days

    asked by Stephanie on October 31, 2008
  32. physics

    if you have an element that starts out at 40g and has a half-life of 10 days, you keep it for 30 days- how much doe you end up with? .

    asked by sandy on April 7, 2011
  33. Pre-Calc

    A radioactive isotope has a half life of 8.1 days. If the sample starts with 25 grams, how much will there be after 90 days?

    asked by Jennifer on November 3, 2014
  34. chem

    The half-life of is 30.0 days. What fraction of a sample of this isotope will remain after 16.2 days?

    asked by sarah on April 27, 2013
  35. chemistry

    Ba-140 has a half life of 13.0 days. What fraction of a sample will remain after 39 days?

    asked by Lily on May 22, 2010
  36. CHEM

    An isotope has a half life of 56 days. It now has 10,000DPM/ml. What will its activity be 100 days from now?

    asked by Jared on April 17, 2013
  37. chemistry

    The half life of phosphorus -32 is 14.3 days. What percentage of an original samples radioactivity remains after 57.2 days?

    asked by matt on May 7, 2012
  38. Chemistry

    A particular radioactive element has a half life of 10.0 days. How much is left after 30.0 days if the sample started with 345g?

    asked by Please help on November 2, 2016
  39. earth science

    if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days

    asked by lan on November 29, 2012
  40. Math

    The half-life of radon-222 is 3.8 days. How much of a 300 gram sample is left after 14.8 days?

    asked by Anonymous on July 30, 2018
  41. earth science

    if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days

    asked by lan on November 29, 2012
  42. earth science

    if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days

    asked by lan on November 29, 2012
  43. Algebra

    The half-life of radon-222 is 3.8 days. How much of a 300 gram sample is left after 14.8 days?

    asked by Anonymous on August 3, 2018
  44. ALGEBRA

    You have 480 grams of a radioactive kind of tin. If its half-life is 10 days, how much will be left after 30 days?

    asked by Anonymous on March 21, 2012
  45. Science

    The half-life of randon-222 is 8 days. What was the original mass if 6 grams remains after 24 days?

    asked by Sarah on February 19, 2016
  46. math

    If, initially, there is 20 mg of gold-198 (198Au) (half-life = 2.696 days), how many days does it take for less than 1 mg to remain?

    asked by anonymous on February 5, 2018
  47. Chemistry

    A radioactive element has a half-life of 6.41 days. What percent of the original sample will be left after 15.0 days?

    asked by John on January 6, 2013
  48. science

    The iodine-131 nuclide has a half-life of 8.0 days. If you originally have a 257 g sample, after 48 days how much will you have?

    asked by emma on May 5, 2017
  49. Algebra 2

    A particular radioactive element has a half life of 10.0 days. How much is left after 30.0 days if the sample started with 345g?

    asked by Please help on November 2, 2016
  50. Chem

    A radiation lab orders 64uCi of P-32. After 42 days the activity of the sample is 8.0uCi. What is the life of P-32? Thanks

    asked by Emily on October 19, 2011
  51. algebra

    the isotope has a very short life of 13 half-life days. estimate the percentage of the original amount of the isotope released by the explosion that remains 3 days after the explosion?

    asked by bob on April 16, 2015
  52. physics

    The half-life of Th(227) is 18.72 days. It decays by alfa emission to Ra(223), an alfa emitter whose half-life is 11.43 days. A particular sample contains 10^6 [10E(+6)] atoms of Th(227) and no Ra(223) at time t=0. a) How many atoms of each type will be in

    asked by Mag on November 6, 2014
  53. Chemistry

    A radioactive sample contains 3.25 1018 atoms of a nuclide that decays at a rate of 3.4 1013 disintegrations per 26 min. (a) What percentage of the nuclide will have decayed after 159 d? % (b) How many atoms of the nuclide will remain in the sample? atoms

    asked by Trixie T on April 16, 2010
  54. Energy

    If the half life of Ir - 131 is 42 days, how much would be remaining after 168 days?

    asked by katie on October 6, 2016
  55. chemistry

    the half-life of radon-222 is 3.823 days. what was the original mass if 0.050g remains after 7.646 days?

    asked by Anonymous on October 21, 2010
  56. Chemistry

    Uranium-238 has half life of 4.51 * 10^9 years Uranium-234 has half life of 2.48 * 10^5 years Thorium-230 has half life of 8.0 * 10^4 years Radium-226 has half life of 1.62 * 10^3 years Lead-210 has half life of 20.4 years. The rate constant for the decay

    asked by Harry on March 20, 2012
  57. Chemistry

    The iodine-131 nuclide has a half-life of 8 days. If you originally have 625-g sample, how many grams will you have after 2 months(approximately 64 days)?

    asked by Please help on November 2, 2016
  58. Physical Science- Help Please!

    Suppose that you are given a 100 gram sample of a radioactive substance with a half-life of 32 days. How many grams will be left after 192 days?

    asked by Molly on December 5, 2012
  59. UIW

    Neptunium-239 has a half-life of 2.35 days. How many days must elapse for a sample of 239Np to decay to 0.100% of its original quantity

    asked by Anonymous on September 19, 2013
  60. chemistry

    Iodine-131 has a half-life of 8 days. How many grams of a 12 g sample will remain at the end of 40 days? how do i solve this? i thought it was 12^40=1.5 but that's wrong...

    asked by jess on November 18, 2010
  61. Math

    You have just isolated a new radioactive element. If you can determine its half-life, you will win the Nobel Prize in physic. You purify a sample of 2 grams.One of you colleges steals half of it, and 3 days later you find that 0.1 grams of the radioactive

    asked by Eric on September 16, 2014
  62. Science Half Lives

    I am confused about how to claculate half lives. Can you explain. ( How much of a 400 gm sample od gold is left after 10.8 days if the half life is 2.7)

    asked by Krys on January 25, 2011
  63. algebra

    Consider that the half-life of Polonium-210 is 140 days.What approximate daily percentage of decay does Polonium-210 demonstrate?% (Round to two decimals.)(Hint: use the Rule of 70 backwards by dividing by the half-life period instead of the rate.) What

    asked by Tristan on October 1, 2015
  64. Physics 30

    The activity of a sample of a radioactive isotope is 1800Bq. If this isotope has a half-life of 16 days, what is the activity after 16 days?, 24 days?, and 60 days?

    asked by Matthew on January 9, 2011
  65. math

    iodine 131 has a half life of 8 days. If 5 mg are stored for a week, how much is left? How many days does it take before only 1 mg remains? An explanation for each step would be nice please. I want to learn how to do these problems for my upcoming exam.

    asked by shannon ortiz on April 19, 2017
  66. Chemistry

    What is used to tell different isotopes of a particular element apart? A. the mass number B. the atomic number C. the number of protons D. the number of electrons A is the answer. After how many half-lives are there equal amounts of parent and daughter

    asked by Derrick on July 19, 2010
  67. Chemistry (Dr.Bob222)

    The half-life of P-32 is 14 days. How long after a sample is delivered can a laboratory wait to use a sample in an experiment if they need at least 10 percent of the original radioactivity? I need help on how to set up this problem. What is the general

    asked by K on November 7, 2013
  68. calc

    The half-life of polonium is 139 days, but your sample will not be useful to you after 95 % of the radioactive nuclei present on the day the sample arrives has disintegrated. For about how many days after the sample arrives will you be able to use the

    asked by barb on April 10, 2007
  69. Science

    Radium has a half-life of 1620 years and decays into radon, which has a half-life of 3.82 days. A 10-gm source of radium is sealed, and the radon produced is pumped off every 24 hours. How many mill curies of radon are pumped off each time?

    asked by Nivia on September 30, 2012
  70. Chemistry

    If a 300g sample of a substance has a half-life of 5 days, how much of the substance will decay after 22 days? A)293.4 g B)290.6 g C)285.8 g D)299.9 g

    asked by Spencer on June 22, 2018
  71. chemistry

    A radioactive sample contains 2.45g of an isotope wiht a half life of 3.8 days. How much of the isotope in grams remains after 11.4 days? please explain

    asked by Monique on November 26, 2011
  72. Chemistry

    Ba-140 has a half life of 13.0 days. What fraction of a sample of Ba-140 will remain after 39 days? A. 1/8th B. 1/16th C. 1/2th D. 1/4th

    asked by Charleze on May 23, 2010
  73. Chemistry

    2. The half-life of a radioactive element is important when considering its application in medicine. For example, iodine-131 is often used in the imaging of the thyroid. The reason is that iodine is readily absorbed by the thyroid gland. Another reason is

    asked by Mickey on September 28, 2014
  74. chemistry

    The half-life of I-131 is 8.00 days. If a medical treatment involves a dose of 400. mg of I-131, how much of the isotope remains after 48 days? 3.125 mg 6.25 mg 12.5 mg 25 mg

    asked by Tamera on December 2, 2014
  75. calculus

    The half-life of Radium-223 is 11.43 days. If a sample has a mass of 400 mg, find the mass (in mg) that remains after 6 days

    asked by w on October 14, 2014
  76. calculus

    The half-life of Radium-223 is 11.43 days. If a sample has a mass of 900 mg, find the mass (in mg) that remains after 5 days

    asked by Connor on October 14, 2010
  77. chemistry

    the half life radium-222 is 4 days. if a sample of radon-222 undergoes decay for 12 days, how much of the original parent isotope will be left?

    asked by Anonymous on May 11, 2017
  78. Science

    Which type of radiation emits particles of helium nuclei? alpha radiation beta radiation induced radiation gamma radiation I think a or d

    asked by Michael on November 10, 2017
  79. Math/Calculus

    After 5 days, a particular radioactive substance decays to 37% of its original amount. Find the half life of this substance. Is this right? Th= ln 2/ln(1/.37) x 5 days

    asked by Christine on October 17, 2011
  80. Chemistry

    The half-life of 131I is 8.021 days. What fraction of a sample of 131I remains after 24.063 days? 1/2 1/4 1/8 1/16 Please help. Thank you

    asked by Kiki on January 24, 2014
  81. Math

    I need help in algebra 1. I have 4 questions, I already answered 3 of them, but I need help with the other Andrew measures the amount of a very unstable substance to be 100 moles. The half-life of this substance is 3 days (after 3 days, half is gone). 1.

    asked by Ayriel on February 8, 2016
  82. 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 of 100 mg to decay to 51

    asked by Rachel on May 18, 2013
  83. chemisty

    Chromium-51 is a radioisotope that is used to assess the lifetime of red blood cells The half-life of chromium-51 is 27.7 days. If you begin with 30.1 mg of this isotope, what mass remains after 44.6 days have passed?

    asked by chan on September 10, 2017
  84. chemistry

    A radioactive sample contains 2.45 g of an isotope with a half-life of 3.8 days. How much of the isotope in grams will remain after 11.4 days?

    asked by Jacques on March 14, 2014
  85. Chemistry

    Mefenamic acid (Ponstan Forte) has a half life of 2 hours. Naproxen has a half life of 12 to 17 hours. Both are anti inflammatory drugs of apparently similar nature but could someone please explain the difference in half life? Thank you Mike

    asked by Mike on August 13, 2009
  86. Chemistry

    The half-life of iodine -131 is 16 days. If you start with 100 gram sample, how many half-lives have past when you have less than a gram left?

    asked by Taylor on October 28, 2007
  87. Chemistry

    The half-life of phosphorus-32 is 14.26 days. The decay constant is k=4.86×10−2/days. If you accidentally spill phosphorus-32 onto your shoe, how long would it take before 99.9% of the radioactive material has decayed so that you can safely wear the

    asked by Anonymous on May 1, 2011
  88. Science math

    Suppose a laboratory has a 38 g sample of polonium-210. The half-life of polonium-210 is about 138 days. How many half-lives of polonium-210 occur in 1104 days? How much polonium is in the sample 1104 days later?

    asked by Joshua on January 7, 2013
  89. science

    Suppose a laboratory has a 31 g sample of polonium-210. The half-life of polonium-210 is about 138 days. How many half-lives of polonium-210 occur in 966 days? How much polonium is in the sample 966 days later?

    asked by Anonymous on March 19, 2013
  90. sciencemath

    Suppose a laboratory has a 31 g sample of polonium-210. The half-life of polonium-210 is about 138 days. How many half-lives of polonium-210 occur in 966 days? How much polonium is in the sample 966 days later?

    asked by Anonymous on March 19, 2013
  91. physics

    The half life of a radioactive sample is 6.93 days.after how many days will only one -tenth of the sample be left behind?

    asked by Mira on August 1, 2012
  92. chemistry

    The radioactive isotope, phosphorus-32, has a half-life of 14.26 days. How much phosphorus-32 will remain after 60 days? Please help.

    asked by Ken on September 3, 2015
  93. Chemistry

    The radioactive isotope, phosphorus-32, has a half-life of 14.26 days. How much phosphorus-32 will remain after 60 days? Please help.

    asked by Anonymous on December 18, 2018
  94. SCIENCE

    .) Iodine 131 is a radioactive waste product generated in nuclear power plants. It has a half life of 8 days. If 16 grams was released from the Fukushima power plant 32 days ago, how much is left now?

    asked by BOB on November 4, 2015
  95. Chemistry 212

    The isotope californium-252 has a half life of 162 days. How many days would it take for 61.7% of the original material to decay? I am using the equation t= (ln(nt/no))/ k and I am first solving for K using: k=(.693/t1/2) the suppose answer can range from

    asked by Valerie on May 6, 2017
  96. Physics

    The isotope, Carbon-14 emits beta radiation and has a half live of 5730 years. How long will it take for the amount of radiation this gives off to drop by a factor of 4?

    asked by Alea on April 8, 2016
  97. Chemistry

    Po-210 Ia an alpha emitter with a half-life of 138 days. how many grams of Po-210 remain after 552 days if the sample initially contained 5.80g of Po-210?

    asked by Shay on October 20, 2014
  98. Chemistry

    Compute the volume of helium at 1.0 atm and 298 K that will be collected if 2.5 g of 222Rn is stored in a container able to expand to maintain a constant pressure for 15 days. Assume that 222Rn decays to 218Po with a half-life of 3.824 days.

    asked by Sandy on December 11, 2012
  99. Chemistry

    27. Excess exposure to nuclear radiation can cause harm. All of the following statements about radiation are true EXCEPT A. Radiation can damage living tissue because of the high energy associated with the radiation. B. Radiation can damage biological

    asked by Emily on June 8, 2014
  100. Engineering Math

    An unknown radioactive element decays into non-radioactive substances. In 120 days the radioactivity of a sample decreases by 59 percent. What is the half life of the element? How long will it take for a sample of 100 mg to decay to 77 mg? The answer is

    asked by Erica on September 23, 2016