Sunday

April 20, 2014

April 20, 2014

Number of results: 11,079

**Science- Radioactive Dating**

Which of the following statements about radioactive dating is true? a. Radioactive decay is the rate at which new atoms form. b. During radioactive decay, atoms break down, releasing particles or energy. c. The rate of decay of a radioactive element cannot be approximated. d. ...
*Thursday, October 10, 2013 at 2:41pm by Anonymous*

**Chemistry**

How many half lives will it take for a sample of a radioactive isotope containing 20000 radioactive nuclei to decay to 2000 radioactive nuclei
*Tuesday, November 16, 2010 at 7:41pm by Dianne*

**MATH!**

The mass of a radioactive substance follows an exponential decay model, with a decay rate of 5% per day. A sample of this radioactive substance was taken six days ago. If the sample has a mass of 3 kg today, find the initial mass of the sample. Round your answer to two decimal...
*Thursday, March 15, 2012 at 8:53pm by Kim*

**math30**

The mass of a radioactive sample is represented in the graph below. The initial mass of 32 mg decays to 8 mg after 21 hours. 1)What is the half-life of the radioactive sample, in minutes? 2)Solve each equation. a. 4 8x-1 = 8 b. 3^(2x-5) = 1/27x
*Tuesday, July 3, 2012 at 4:16am by alejandro*

**Calculus-Modeling Equations**

An unknown radioactive element decays into non-radioactive substances. In 420 days the radioactivity of a sample decreases by 39 percent. 1.What is the half-life of the element? 2.How long will it take for a sample of 100 mg to decay to 46 mg?
*Friday, March 6, 2009 at 12:08am by Kim*

**science**

A 10g sample of radioactive substances is lift to decay for five half-lives. How much of the radioactive substance remains?
*Tuesday, February 19, 2013 at 3:51pm by mirian hernandez*

**calculus**

The rate at which an amount of a radioactive substance decays is modeled by the differential equation dA/dt = kA, where A is the mass in grams, t is the time in years, and k is a constant. Answer the following. a) If a 100-gram sample of the radioactive substance decays to 95 ...
*Monday, March 19, 2012 at 12:43pm by ronnieday*

**Chemistry**

If a 100.0 gram sample of a radioactive isotope goes through three half-lives, how much of the original radioactive isotope will remain?
*Thursday, January 24, 2013 at 9:17pm by OhSnap*

**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 mg? time needed:
*Saturday, May 18, 2013 at 4:06am by Rachel*

**chemistry**

The idea is to use an isotope of O or make O radioactive and use that to produce CO2 or H2O (that is make O different so you can find it). Then (if you made O radioactive) measure the glucose and the O2 and see if the O2 is radioactive or if the glucose is radioactive. Let's ...
*Monday, April 15, 2013 at 12:04am by DrBob222*

**chemistry**

a radioactive material is undergoing nuclear decay. After 40 minutes, 25% of the sample remains. What is the half-life of the sample
*Saturday, August 27, 2011 at 9:00am by marjani*

**8th Grade Earth Science Help?**

Which of the following terms refers to the time it takes for one-half of the radioactive atoms in a sample of a radioactive element to decay? - relative age - absolute age - potassium-argon data - half-life** Is my answer correct?
*Tuesday, January 14, 2014 at 7:05pm by Rainshine*

**science **

The half-life of carbon 14 is 5730 years. if a 1 g sample of old carbon is 1/8 as radioactive as 1 g of a current sample, then the age of the old sample is about ___________years. 22,900 17,200 11,500 716
*Monday, March 5, 2012 at 3:49pm by chuck *

**Chemistry**

6CO2 + 6H2O ==> C6H12O6 + 6O2 Make O in CO2 radioactive; see where the radioactive O is at the end. Make O in H2O radioactive; see where the radioactive O is at the end.
*Sunday, April 14, 2013 at 11:52pm by DrBob222*

**Physcis 30**

Q1) If there are 100 radioactive atoms with a half-life of 30 seconds, how many radioactive atoms will remain after one half-life (30 seconds)? How many will remain after two half-lives (60 seconds)? Three half-lives? So basically, after 30 seconds it will be 50.After 60 sec. ...
*Thursday, January 6, 2011 at 11:13am by Marium*

**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?
*Wednesday, August 1, 2012 at 2:37am by Mira*

**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?
*Tuesday, May 5, 2009 at 10:06am by Anonymous*

**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 radioactive material is ...
*Sunday, October 21, 2012 at 2:34pm by Roseanne*

**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?
*Wednesday, September 26, 2012 at 2:30pm by Shay*

**Physics**

Consider a radioactive sample with a half-life of one week. How much of the original sample will be left at the end of the second week? The third week? The fourth week?
*Thursday, August 29, 2013 at 2:13pm by Tracee*

** Chem**

A radioactive isotope sample has a hal
*Friday, December 6, 2013 at 2:37am by Lulu*

**Chemistry**

A 50.6 mg sample of sodium perchlorate contains radioactive chlorine-36 (whose atomic mass is 36.0 amu). If 29.6% of the chlorine atoms in the sample are chlorine-36 and the remainder is naturally occurring nonradioactive chlorine atoms, how many disintegrations per second are...
*Monday, February 13, 2012 at 4:33pm by Steven*

**Problem**

If an Elements has a half life of 20mins what is the radioactive decay of a 200gram sample?
*Tuesday, June 11, 2013 at 4:47pm by Half life*

**science/math**

write and solve an algebraic equation to find the original mass of the sample of the radioactive isotope uranium -235, which has a half-life of 704 million years your sample is about 700 million years old and weighs 120 grams
*Tuesday, November 27, 2012 at 11:55pm by Justin*

**calculus**

Carbon-14 is a radioactive substance produced in the Earth's atmosphere and then absorbed by plants and animals on the surface of the earth. It has a half-life (the time it takes for half the amount of a sample to decay) of approximately 5730 years. Using this known piece of ...
*Friday, July 24, 2009 at 1:11pm by j*

**science **

after six half-lives what percentage of a radioactive sample will remain? a) 0%-1% b) 1%-3% c) 3%-6% d) 6%-10%
*Monday, December 9, 2013 at 8:16pm by victoria *

**calculus**

A sample of a radioactive substance decayed to 94.5% of its original amount after a year. (Round your answers to two decimal places.) (a) What is the half-life of the substance? (b) How long would it take the sample to decay to 65% of its original amount?
*Friday, November 9, 2012 at 6:00pm by kela*

**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 polonium? you want to ...
*Tuesday, April 10, 2007 at 11:46pm by barb*

**chemistry**

a radioactive material is undergoin nuclear decay. After 40 minutes, 25% of the sample remains. What is the half life of the sample? Pls say the formula how to calculate it a)10 mins b) 20 mins c) 40 mins d)80 mins e) 160 mins
*Monday, May 28, 2012 at 10:38am by star*

**Physics**

If a sample of a radioactive isotope has a half-life of 5 year(s), how much of the original sample will be left at the end of the second year? How much will be left at the end of the third year of thr original sample? How much will be left at the end of the fourth year of the ...
*Monday, November 23, 2009 at 7:19pm by TITA*

**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 contains 1.22E+21 nuclei?
*Friday, April 18, 2008 at 9:16pm by Sandhya*

**Chemistry**

As a sample of the radioactive isotope 131 I decays, its half-life a)decreases b)increases c)remains the same
*Wednesday, May 5, 2010 at 7:04pm by Danny*

**Chemistry *URGENT***

URGENT help! 3. A rock sample was dated using potassium-40, Neasyrenebt ubducated tgat 1/8 of the original parent isotope is left in the rock sample. How old is the rock? 5. When a sample of lava solidfied, it contained 28g of uranium-238. It that lava sample was later found ...
*Friday, March 5, 2010 at 4:49am by Anon*

**Calc**

A sample of a radioactive substance decayed to 93.5% of its original amount after a year. a) What is the half-life of the substance? ? years (b) How long would it take the sample to decay to 10% of its original amount? ? years
*Sunday, November 8, 2009 at 7:47pm by Lee*

**chemistry**

I really don't know how to answer this question because H, the fist element in the periodic table, has a radioactive isotope. Also, carbon, near the beginning, and Po, Ra, U, and a host of others at the end of the table are radioactive naturally. There are some naturally ...
*Monday, June 2, 2008 at 7:55pm by DrBob222*

**chemistry**

what fraction of an original sample of a radioactive isotope remains after three half-lives have passed? 1/8?
*Saturday, October 13, 2012 at 12:43pm by jake*

**chemistry**

How long will it take for 25% of the C-14 atoms in a sample of C-14 to decay? The half-life for the radioactive decay of C-14 is 5730 years. If a sample of C-14 initially contains 1.1 mmol of C-14 , how many millimoles will be left after 2275 years?
*Sunday, February 28, 2010 at 2:17pm by Anonymous*

**science**

suppose you had two samples of the same radioactive isotope. one sample had a mass of 25 grams. the other had a mass of 50 grams. would the same number of particles be ejected from each sample in the first hour? explain
*Thursday, November 11, 2010 at 10:28pm by hannah*

**Science**

If a radioactive isotope has half life of 5 days,how long will it take for its radioactive strength to be a maximum of one thousandth,(1/1000) of its original value?
*Tuesday, December 21, 2010 at 6:59pm by Bree*

**qnt/351**

Which of the following statements about the two sample sizes is NOT true? Assume thepopulation standard deviations are equal A. Sample A = 11; sample B = 13 B. Sample A = 12; sample B = 14 C. Sample A = 13; sample B = 13 D. Sample A = 10; sample B = 16
*Monday, March 31, 2014 at 2:10pm by arelis*

**Chemistry (Grade 11)**

A radioactive sample of 141Cs has a half-life of 32.5 days. In a sample that contains 8.00*10^7 nuclei of 141Cs, how many beta particles per second will be emitted? A 19.8 B 1.7*10^6 C 71 076 D 1185 E 2.47*10^-7 The 141 supposed to be a superscript text, but firefox won't let ...
*Wednesday, February 3, 2010 at 7:03pm by David*

**chemistry**

The question I am having trouble with is: Scientists originally were uncertain whether the oxygen gas produced during photosynthesis came from CO2, H2O, or from both. How could radioisotope tracers be used to settle that question? Chemistry - DrBob222 6CO2 + 6H2O ==> ...
*Monday, April 15, 2013 at 12:04am by Madison*

**PHYS**

Help! Initially there are 6x10^9 radioactive of element W (decay constant 0.173/day) in a sample. As a nucleus of W decays, it converts 2.67x10^-28 kg of its mass to energy and releases the energy. How much time (in days) is required for the sample to releae a total of 7.2x10...
*Monday, April 25, 2011 at 4:46pm by Jenn*

**Science**

What can scientists learn from the rate at which radioactive elements decay? A. a rock's absolute age* B. the relative age of rock layers C. where one soil horizon ends and the next begins D. the difference between molds and casts. After six half-lives, what percentage of a ...
*Tuesday, October 15, 2013 at 11:46am by Anonymous*

**Science**

What can scientists learn from the rate at which radioactive elements decay? A. a rock's absolute age* B. the relative age of rock layers C. where one soil horizon ends and the next begins D. the difference between molds and casts. After six half-lives, what percentage of a ...
*Wednesday, October 16, 2013 at 1:58am by Anonymous*

**Science**

What can scientists learn from the rate at which radioactive elements decay? A. a rock's absolute age* B. the relative age of rock layers C. where one soil horizon ends and the next begins D. the difference between molds and casts. After six half-lives, what percentage of a ...
*Wednesday, October 16, 2013 at 3:03pm by Anonymous*

**chemistry -- radioactive decay **

suppose you have a 150 gram sample of radioactive decay god-191 which has a half- life of 3.4 hours. how many grams of gold will ramain after 10hrs ? after 24 hrs? answer : 10 hrs :10/3.4= 2.94 times 150*(1/2)^2.94 = 18.75 grams 24 hrs: 24/3.4 = 7.06 150*(1/2)^7.06= 1.12 right...
*Tuesday, September 18, 2012 at 11:53pm by Maria*

**Geology**

How do I do the foll9owing example? K-40 - A-40 (1.25 billion years) After careful analysis, a geochronologist determines that an unweathered, unmetamorphosed mineral sample contains 7 trillion atoms of the radioactive element K-40 and 105 trillion atoms of its decay product A...
*Thursday, October 25, 2012 at 6:40pm by Nicole*

**physics**

If a radioactive isotope has a half-life of 1 year, how much of the original sample will be left at the end of the 2nd year?
*Thursday, August 23, 2012 at 9:50am by Anonymous*

**science - biology**

A photosynthesis experiment uses Chlorella to track the route taken by 14C in photosynthesis. The 14C is provided from CO2 and no new sources of CO2 are available. After the experiment the scientist extracts all of the starch produced and analyses the Carbon present. She ...
*Saturday, May 7, 2011 at 8:57am by jack*

**CHEMISTRY**

Suppose you had a detection device that could count every decay event from a radioactive sample of plutonium-239.052156 (t1/2 is 24,000 yr). How many counts per second would you obtain from a sample containing 0.126 g of plutonium-239? (The mass of Pu-239 is 239.052156 u. ...
*Wednesday, September 5, 2012 at 9:17pm by Maryanne*

**Science**

if a radioactive isotope has a half-life of one year, how much of the original sample will be left at the end of the second year?
*Thursday, August 23, 2012 at 9:53am by aileen*

**Science**

if a radioactive isotope has a half-life of one year, how much of the original sample will be left at the end of the second year?
*Thursday, August 23, 2012 at 9:59am by aileen*

**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?
*Sunday, January 6, 2013 at 2:27pm by John*

**chemistry**

yes, i do mean isotopes that undergo radioactive decay. However i do not really understand what this radioactive thing have to do with isotopes or unstable or stable.
*Saturday, February 7, 2009 at 8:46am by Nabiha*

**Science**

If a radioactive isotope has half life of 5 days,how long will it take for its radioactive strength to be a maximum of one thousandth,(1/1000) of its original value? Can anyone give me a VERY SIMPLE explanation of this please? Thank you.
*Saturday, January 29, 2011 at 9:31pm by Korina*

**biology**

14 points Save A photosynthesis experiment uses Chlorella to track the route taken by 14C in photosynthesis. The 14C is provided from CO2 and no new sources of CO2 are available. After the experiment the scientist extracts all of the starch produced and analyses the Carbon ...
*Saturday, May 7, 2011 at 9:01am by jack*

**Science- Earth and its History**

What can scientists learn from the rate at which radioactive elements decay? A. a rock's absolute age* B. the relative age of rock layers C. where one soil horizon ends and the next begins D. the difference between molds and casts. After six half-lives, what percentage of a ...
*Tuesday, October 15, 2013 at 3:18pm by Anonymous*

**chemistry**

I'm not sure what you mean by stable; however, I thought all of them were stable at 0 C except for Rn which is radioactive. Some of the others have radioactive isotopes.
*Tuesday, February 23, 2010 at 3:53pm by DrBob222*

**Chemistry**

If 30% of a sample of radioactive isotope decays in 24 hrs, what is the half-life? How do i know which order to use? and do I convert hr to mins or seconds? Pls help for my exam tomorrrow
*Thursday, February 23, 2012 at 2:44pm by tina*

**chemistry**

if you start with 100mg of radioactive material that has a half life of one hour, how many mg's of radioactive material would you have in 10.2284952 hours?
*Tuesday, February 1, 2011 at 2:12pm by carlos*

**Science**

If a 20 gram sample of a radioactive substance has a half-life of 6000 years, how many grams would be present after 18000 years?
*Wednesday, December 5, 2012 at 4:21pm by Owen*

**chemistry**

use logic and simple math to determine how long it will take for a sample of potassium- 42 to decay from 8mg to 0.25mg if the half-life of this radioactive isotope is 124 hours
*Tuesday, October 12, 2010 at 8:29pm by jay 1*

**Chem 2**

The half-life for the radioactive decay of U-238 is 4.5 billion years and is independent of initial concentration. a) How long will it take for 10% of the U-238 atoms in a sample of U- 238 to decay? b)If a sample of U-238 initially contained 1.9×1018 atoms when the universe ...
*Thursday, July 21, 2011 at 9:55pm by Kristina*

**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?
*Wednesday, December 5, 2012 at 4:13pm by Molly*

**College algebra**

The radioactive element has a half-life of about 28 years and sometimes contaminates the soil. After 47 years, what percentage of a sample of the elements remain?
*Sunday, May 12, 2013 at 4:20pm by Taylor*

**physics**

The half-life of a certain radioactive isotope is 32 hours.What fraction of the sample would remain after 16 hours?(a)0.50(b)0.25(c)0.62(d)0.71
*Sunday, September 22, 2013 at 1:11pm by john*

**Math**

How do I solve this if there is no equation to this 1. The population of the bacteria in a Petri dish increases by a factor of 10 every 10 hour. If there are initally 20 bacteria in the dish, how long will it take before the population increases to 60,000 to the nearest tenth ...
*Saturday, January 28, 2012 at 9:34pm by Jake*

**chemistry**

The radioactive waste must be discarded. The problem is that many of the radioactive isotopes have half lives of many years (some thousands of years) so where do we store that stuff and keep it out of harms way with no damage to humans or to the environment?
*Monday, November 14, 2011 at 8:43pm by DrBob222*

**Physics **

Hi Radioactive decay - A radioactive nuclide has a decay constant of - 10^-6 s-1 what is its half life ? I have come up with is IN (2) / 0.000001 s-1 = 693147.18055 which iam having troube working into real figures Can anyone help please .. thanks
*Saturday, August 24, 2013 at 8:27am by Freddo*

**Physics ... **

Hi Radioactive decay - A radioactive nuclide has a decay constant of - 10^-6 s-1 what is its half life ? I have come up with is IN (2) / 0.000001 s-1 = 693147.18055 which iam having troube working into real figures Can anyone help please .. thanks
*Saturday, August 24, 2013 at 3:44pm by Freddo*

**Chemistry**

If the amount of radioactive iodine-123 in a sample decreases from 0.8 g to 0.1 g in 36.2 hours, what is the half-life of iodine-123
*Sunday, April 17, 2011 at 10:22am by Sara*

**Physics check**

Why does a hydrogen bomb produce significant radioactive fall-out? A hydrogen bomb operates with a nuclear reaction that produces radioactive products?
*Friday, April 25, 2008 at 8:22pm by Emily*

**precal**

If the half-life of a certain radioactive substance is 2000 years, estimate how many years must elapse before only 35% of the radioactive substance remains?
*Tuesday, January 22, 2013 at 10:15pm by james*

**science**

during radioactive decay atoms of a radioactive element break down and change into other atoms of another element-all at once a) true b) false
*Wednesday, December 11, 2013 at 12:56pm by victoria*

**Chemistry**

A 208 g sample of sodium-24 decays to 13.0 g of sodium-24 within 60.0 h. What is the half-life of this radioactive isotope?
*Tuesday, December 11, 2012 at 11:08pm by Matthew*

**chemistry**

if the amount of radioactive iodine-123 in a sample decreases from .400g to .100g in 26.2 hours, what is the half-life of iodine-123
*Thursday, April 18, 2013 at 7:23pm by j*

**physics**

if 5/6th of a radioactive sample decay in 70 years and 1/6th remain. how can you find the half life without knowing the decay constant can you help?
*Wednesday, May 21, 2008 at 5:51am by ronny*

**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?
*Friday, March 14, 2014 at 10:40am by Jacques*

**College Algebra**

The half-life of a radioactive material is about 34.6 years. How much of a 1-gram sample of the material is left after 30 years?
*Saturday, October 20, 2012 at 12:21am by Anonymous*

**TO ANY SCIENCE HELPER**

I honestly don't get how to use radioactive dating to determine the age of a sample. I need an example and what to do in order to get the answer. I need it to be step by step. Thank u so much :)
*Thursday, April 17, 2014 at 8:48pm by Anonymous *

**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
*Saturday, November 26, 2011 at 11:38am by Monique*

**Chemistry**

radioactive sodium chloride is appropriate for diagnosing circulatory problems, but radioactive xenon is helpful in searching for lung problems. Explain why. I understand different elements are used for specific parts of the body but I don't understand this question. Thanks ...
*Sunday, April 14, 2013 at 8:06pm by Sara*

**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?
*Sunday, May 16, 2010 at 8:59am by Anonymous*

**12th grade**

The radioactive isotope of Carcon (^14C)has a half life of 5730. What is the decay constant of ^14C? If we start with a sample of 1000 carcon nuclei, how many will be left in 22920 years time?
*Thursday, April 8, 2010 at 12:34pm by Moe*

**Pre-Cal**

The radioactive isotope of Carcon (^14C)has a half life of 5730. What is the decay constant of ^14C? If we start with a sample of 1000 carcon nuclei, how many will be left in 22920 years time?
*Thursday, April 8, 2010 at 1:43pm by Moe*

**chemistry**

Naturally occurring cobalt consists of only one isotope Co59 whose relative atomic mass is 58.9332. A synthetic radioactive isotope of cobalt Co60, relative atomic mass 59.9338, is used in radiation therapy for cancer. A 1.8516 sample of cobalt has an apparent "atomic mass" of...
*Saturday, June 30, 2012 at 4:22pm by Candace*

**Math**

Is drawing students names out of a hat a good example? Which type of sample is it? Simple random sample Systematic random sample Voluntary response sample Convenience sample Or Stratified random sample. Thank you.
*Tuesday, September 2, 2008 at 5:33pm by Happyface*

**Physics**

A certian radioactive isotope has a half-life of 1 hour. If you start with 1 gram of the material at noon, how much of the original isotope will the sample contain at 3 pm? At 6 pm? At 10 pm?
*Saturday, November 17, 2007 at 12:41pm by Judy*

**Chemistry**

The half-life for radioactive decay of 14C is 5730 years (it emits β-particles with energy of 0.16 MeV). An archaeological sample contained wood that had only 72% of the 14C found in living trees. What is its age?
*Thursday, April 8, 2010 at 4:02pm by Zoa*

**Math**

After 150 thousand years, only 1/8 of the original amount of a particular radioactive waste will remain. The half-life of this radioactive waste is how many thousand years?
*Tuesday, August 20, 2013 at 9:23am by Joy*

**Chemistry**

Which radioactive sample would contain the greatest remaining mass of the radioactive isotope after 10 years? A. 2.0 grams of 198 Au B. 2.0 grams of 42 K C. 4.0 grams of 32 P D. 4.0 grams of 60 Co By the way the numbers next to the elements are their atomic masses. thanks ...
*Saturday, March 3, 2007 at 8:50pm by Sanjay*

**PLEASE HELP ME! CHEMISTRY**

Naturally occurring cobalt consists of only one isotope, cobalt59, whose relative atomic mass is 58.9332. A synthetic radioactive isotope of cobalt60, relative atomic mass 59.9338, is used in radiation therapy for cancer. A 1.8155 sample of cobalt has an apparent "atomic mass...
*Monday, August 29, 2011 at 11:14pm by Aidan*

**Chemistry**

A 71 mg sample of a radioactive nuclide is administered to a patient to obtain an image of her thyroid. If the nuclide has a half-life of 12 hours, how much of the nuclide remains in the patient after 4.0 days?
*Tuesday, October 5, 2010 at 7:13pm by Mr.Chemistry*

**Chemistry**

A certain radioactive element has a half life of 1 h. If you start with a 1-g sample of the element at noon, how much is left at 3:00 PM? At 6:00PM? At 10:00 PM?
*Friday, October 8, 2010 at 12:20pm by Jennifer*

**physics**

After 1.84 days, the activity of a sample of an unknown type radioactive material has decreased to 85.8% of the initial activity. What is the half-life of this material? (in days)
*Sunday, June 3, 2012 at 1:43am by andrew*

**Biology- please help :)**

The Hershey-Chase experiment proved that DNA was the hereditary material because? A)radioactive phosphorus in viral proteins was shown not to enter bacterial cells. B)radioactive phosphorus in viral DNA was shown to enter bacterial cells. C)radioactive sulfur in viral proteins...
*Thursday, December 13, 2012 at 4:42pm by TheGirlNextDoor*

**Calculus**

The amount A in grams of radioactive plutonium remaining in a 20-gram sample after t days is given by the formula A=20*(1/2)^(t/140). At what rate is the plutonium decaying when t=2 days?
*Tuesday, November 30, 2010 at 6:29pm by Sara*

**Physical Science**

A gram of radioactive material has a half-life of one year. After four years how much radioactive material will be left...0g, 1/2g, or 1/4g? None of the above. The answer one-half to the fourth power.
*Thursday, March 29, 2007 at 10:24pm by Gina*

**chemistry**

A particular radioactive substance has a half-life of 4 minutes. How long will it take for 250 g of this radioactive material to decay to less than 0.1g? 24 min 36 min 40 min 48 min 72 min I got 32 min but that not one of the choices. Please help
*Monday, December 5, 2011 at 2:53pm by Anonymous*

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