Number of results: 723

**Chem**

The decay constant for a radioactive isotope is 7.82 x 10-6 /y. What is the half-life of this isotope in years?

*January 31, 2015 by Brooklyn*

**earth**

how Earth would be different today, if it contained no radioactive material

*November 3, 2009 by Lizeth*

**Physics**

How many half-lives are required for the number of radioactive nuclei to decrease to 1/10^4 of the initial number?

*July 27, 2012 by Beth*

**Math**

Find the half-life (in hours) of a radioactive substance that is reduced by 10 percent in 5 hours.

*August 28, 2012 by David*

**chem**

what changes in atomic number and mass number occur in a positron emmision of radioactive decay?

*June 2, 2008 by jerson*

**math**

A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.

*February 3, 2011 by Eric*

**math**

A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.

*February 3, 2011 by Eric*

**math**

A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.

*February 3, 2011 by Eric*

**math**

A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.

*February 3, 2011 by Eric*

**math**

A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.

*February 3, 2011 by Eric*

**math**

A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.

*February 3, 2011 by Eric*

**math**

A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.

*February 3, 2011 by Eric*

**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?

*December 11, 2012 by Matthew*

**Environmental Science 11th grade**

If half of a quantity of radioactive material decays in 10 years, in another 10 years?

*February 7, 2013 by AM*

**Health**

What safety and health problems are associated with storing radioactive waste in deep geological repositorites?

*November 13, 2014 by slomo*

**Pre Calculus**

If a 25 mg sample of radioactive material decays to 18.4 mg in 5 years, how long will it take the sample to decay to 20.5 mg?

*November 20, 2014 by Brianna*

**math calculus**

Find the half-life (in hours) of a radioactive substance that is reduced by 30 percent in 40 hours.

*August 30, 2015 by Urgent help*

**chemistry**

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 shoes again?

*May 12, 2011 by brittany*

**Chemistry Numerical**

The half life period of a radioactive element is 27.96 days. Calculate the time taken by a given sample to reduce to 1/8th of its initial activity

*November 20, 2014 by Harsh*

**AP Chemistry**

Which of the following is true about lanthanides? A. they are all radioactive B. they are highly electropositive C. they are very common elements D. they have low melting and boiling points

*January 29, 2016 by Stephanie*

**Pre calc**

If 250 mg of a radioactive element decays to 200 mg in 48 hours, find the half-life of the element

*April 28, 2010 by Dom*

**chemistry**

Which radioactive emanations have a charge of -1? beta particles alpha particles gamma rays neutrons

*April 30, 2012 by david*

**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?

*January 6, 2013 by John*

**Radioactivity**

Iodine-131 is a radioactive isotope. After 8.00 days, 50.2% of the sample remains. What is the half life of 131-I?

*September 28, 2015 by Jessica*

**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?

*October 8, 2010 by Jennifer*

**chemistry**

a radioactive material is undergoing nuclear decay. After 40 minutes, 25% of the sample remains. What is the half-life of the sample

*August 27, 2011 by marjani*

**Calc**

Radioactive radium () has a half-life of 1599 years. What percent of a given amount will remain after years?

*April 15, 2012 by Pamela*

**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?

*August 23, 2012 by Anonymous*

**Physics**

A radioactive substance decays from 2.0kg to 1.6kg in 156 days. What is the decay constant and the half life of the substance?

*August 6, 2013 by Alice*

**Physics**

A radioactive substance decays from 2.0kg to 1.6kg in 156 days. How much will be left after 201 days?

*August 7, 2013 by Alice*

**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

*September 22, 2013 by john*

**isd muscat**

after two hours 1/16th of the radioactive isotope remains undecayed.half life of the isotope is

*April 11, 2014 by saritha*

**Chemistry**

Iodine 131 is a radioactive isotope. After 4.00 days, 70.8% of a sample of 131I remains.What is the half life of 131I?

*April 26, 2014 by Natalie*

**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?

*November 3, 2014 by Jennifer*

**chemistry**

The half-life of C14 radioactive is 5760 yr. After how much time will 200 mg C14 sample be reduced to 25 mg?

*May 3, 2015 by yashpal*

**science**

Can someone help me find two specific reasons why radioactive dating/geology are evidence for evolution. I've read many articles online but i do not really understand the whole concept.

*June 14, 2008 by Anonymous*

**science**

the threat of global warming is mainly associated with ? 1 radioactive wastes 2 use of hydroelectric energy 3 burning of fossil fuels 4 thermal pollution of lakes and rivers

*May 29, 2012 by amber*

**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?

*March 21, 2012 by Anonymous*

**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?

*August 23, 2012 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?

*August 23, 2012 by aileen*

**Math**

An unknown radioactive substance has a half-life of 124 years. How long will it take a 67 grams sample to degrade to 18 grams?

*February 17, 2016 by Maria*

**Algebra**

A radioactive kind of nitrogen has a half life of 10 minutes. If you start with 64 grams of the substance, how much will be left after 20 minutes?

*May 6, 2016 by Ana Y*

**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?

*November 2, 2016 by Please help*

**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?

*November 2, 2016 by Please help*

**math algebra**

The amount A, of 70 grams of a certain radioactive material remaining after t years can be found by the equation A=70(0.62)^t. When will 10 grams remain?

*December 1, 2016 by laura*

**Chemistry**

Thinking about the uses of radioactive isotopes, which statement is true? A. The iodine isotope, I-27, is used to diagnose thyroid disorders. B. Radiation may be detected because it ionizes the atoms it affects. C. Itâ€™s clearly understood that irradiating food kills bacteria...

*June 24, 2010 by Sadie*

**Science**

I'm kinda in a rush but take your time!Thx! 1.What was Henri Becquerel studying when he accidentally discovered radioactivity? A.photography B.properties of black light C.properties of X-rays D.solar energy 2.When Marie Curie isolated uranium from pitchblende, she realized ...

*January 6, 2015 by I am awesome*

**algebra**

Scientists can determine the age of ancient objects by a method called radio carbon dating. The bombardment of the upper atmosphere by cosmic rays converts nitrogen to a radioactive isotope 14C of carbon with a half-life of about 5710 years. Vegetation absorbs carbon dioxide ...

*March 7, 2013 by Emily*

**Chemistry**

The nuclide 12 N 7 is unstable. What type of radioactive decay would be expected??? my guess is either gamma or beta. are either of those correct?

*March 4, 2008 by Jonathan*

**math**

Radioactive radium has a half-life of approximately 1599 years. What percent of a given amount remains after 100 years?

*February 24, 2011 by rachel*

**math**

Radioactive radium has a half-life of approximately 1599 years. What percent of a given amount remains after 100 years?

*February 24, 2011 by rachel*

**math**

The decay of 333 mg of a radioactive substance is given by A(t) = 333e-0.024t, where t is time in years. Find the amount left after 17 years.

*April 8, 2011 by allison*

**Physics**

In the radioactive formula 235 U → 235 Np + X, what does X represent 92 93 A. An Alpha Particle B. A positron C. An electron D. A gamma ray Please help ASAP!!! Thank you :D

*June 3, 2011 by J. J.*

**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?

*December 5, 2012 by Owen*

**Science**

It can be inferred from the passage that radioactive dating is important for estimating the age of A) all known meters B) all existing planets C) the earth D) the trees

*August 11, 2016 by Shelby*

**College Calculus**

A radioactive substance has a half-life of 27 years. Find an expression for the amount of the substance at time t if 20 grams were present initially.

*November 14, 2016 by Jaken*

**science**

I need a picture that describes radioactive decay, fussion and fision. Someone said that they would give me a link earlier but they didnt. Thank you! This website helps me out so much.

*January 15, 2009 by Amy*

**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

*October 12, 2010 by jay 1*

**Chemistry**

Tc-99 is a radioactive isotope that decays by beta emission and is used by radiologists in the diagnosis of liver disease. Its decay behavior is shown by the activity-time table. What is its half-life?

*December 10, 2011 by Jennifer*

**chemistry**

I am having trouble understanding what the concept is for writing these out. Write a balanced nuclear equation for the alpha decay of each of the following radioactive isotopes: curium-243, 22589Ac

*December 5, 2013 by ellie*

**Biology-check my answer**

Hershey and Chase used the 35S isotope to label proteins. How does this isotope differ from the 32S isotope found in greatest natural abundance, and why did they choose 35S instead of 32S? A)35S has more protons than 32S; Hershey and Chase used it because it has a greater mass...

*December 19, 2012 by joey*

**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?

*November 17, 2007 by Judy*

**math**

if the rate for radioactive decay for a substance is r=-.0063 and time is being measured in days how do you find the half-life of the substance to the nearest hour?

*March 30, 2009 by mike*

**physics**

Pick the radioactive isotope in each set 23/11 na or 20/9 f explain why a)its atomic number is greater than 83 b)it has fewer n than p in the nucleus c)it is an odd-odd nuclide none of the above

*September 17, 2010 by Ashley*

**PHYICS**

Pick the radioactive isotope in each set 14/7 N OR 23/13 AL EXPLAIN A)its atomic number is greater than 83 B)it has fewer n than p in the nucleus C)it is an odd-odd nuclide none of the above

*September 18, 2010 by Ashley*

**math**

Show that if a radioactive substance has a half life of T, then the corresponding constant k in the exponential decay function is given by k=-ln(2)/T I'm confused about how to show that that is true.

*September 4, 2014 by lucy*

**Chemistry**

The radioactive nuclide 18F decays by first order kinetics with a half life of 1.83 hr. How many hours will it take for 68.5% of a give quantity of 18F to decay?

*April 27, 2015 by Molly*

**Math**

the half life of a radioactive substance is one day. You have 100 grams. how much of the substance would be left after a week?

*July 30, 2015 by Jo*

**Algebra 2**

A radioactive substance decays at a rate of y = ae^-0.1483t, where t in in hours. Find the half-life of the substance. How do I solve this problem if I am only given the constant.

*December 1, 2015 by Sammantha Avants*

**Pre-Calc**

Tritium, a radioactive isotope of hydrogen, has a half-life of 12.4 years. Of an initial sample of 69 grams, how much will remain after 75 years?

*May 12, 2016 by Anonymous*

**Alg2**

Radioactive iodine is used to determine the health of the thyroid gland. It decays according to the equation y=ae -0.0856t where t is in days. Find the half-life of this substance. Round to the tenths place.

*December 6, 2011 by Rock*

**Alg2**

Radioactive iodine is used to determine the health of the thyroid gland. It decays according to the equation y=ae -0.0856t where t is in days. Find the half-life of this substance. Round to the tenths place.

*December 8, 2011 by Rock*

**American Constitutional Law**

The Low-Level Radioactive Waste Policy Amendments Act established the following as incentives to the states. A. Financial B. Access C. Take Title D. All of the above Is it D?

*February 27, 2015 by Manda*

**Calculus**

A certain radioactive material decays exponetially. The percent, P, of the material left after t years is given by P(t)= 100(1.2)^-t a)Determine the half life of the substance

*April 13, 2010 by lala*

**phyics**

Pick the radioactive isotope in each set. 23/11 20/9 Explain your choice. a)its atomic number is greater than 83 b)it has fewer n than p in the nucleus c)it is an odd-odd nuclide none of the above

*September 17, 2010 by ashley*

**Physics**

In the radioactive formula, 235 U → 235 Np = X, what does X represent 92 93 A. An alpha Particle B. A positron C. An electron D. A gamma ray Please help ASAP!!! Thank you very much!!

*June 3, 2011 by J. J.*

**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?

*May 12, 2013 by Taylor*

**AP Chem ---**

If a radioactive nucleus alpha decays to yield a sodium24 nucleus in 14.8 hours, what was the identity of the original nucleus? Nuclear equation?

*May 22, 2015 by Dani*

**chemistry**

What are some applications of Nuclear Chemistry in Medicine? So far I've found - X-rays - Radioactive tracers - Gamma radiation can be used to treat cancer and other diseases

*March 11, 2008 by william*

**college**

The average number of radioactive particles passing through a counter during 1 millisecond in a lab experiment is 4. What is the probability that more than 2 milliseconds pass between particles?

*February 10, 2010 by ashley*

**statistics**

The average number of radioactive particles passing through a counter during 1 millisecond in a lab experiment is 4. What is the probability that more than 2 milliseconds pass between particles?

*February 10, 2010 by ashley*

**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?

*December 5, 2012 by Molly*

**Chem**

Suppose that you start with 1000000 atoms of a particular radioactive isotope. how many half-lives woruld be required to reduce the number of undecayed atoms to fewer than 1000?

*October 20, 2014 by Shay*

**Elem. Ed.**

b and c, don't you think? the teacher explains and the children practice what has been explained my experience leads to me to the conclusion that actual practice is the best learning technique. I vote for c. sounds good Can you help me with this question? An instructional ...

*April 17, 2007 by jules*

**Physical Science**

I'm still working on getting a fireman to come out to the school to demonstrate a radioactive detector. No luck so far. This is for a project on Marie Curie. Any other suggestions would be greatly appreciated.

*October 10, 2008 by jules*

**Physical Science**

The heat of volcanoes and hot springs comes from trace amounts of radioactive minerals found in the Earth's interior. Why isn't the same rock at the Earth's surface warm?

*March 10, 2008 by Rachel*

**Elem. Ed.----- I Need Help!!!**

Can you help with this question? 1. Charts do not: A. offer an opportunity for shared experiences. B. allow the print to stand out. C. capture the children's attention. D. teach children to read at a very early age. I know charts (A) offer opportunities for shared experiences,...

*September 21, 2007 by Anonymous*

**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?

*May 5, 2009 by Anonymous*

**Chem**

Radioactive 24Na with a half-life of 14.8 hours is injected into an animal in a tracer experiment. How many hours will it take for the radioactivity to fall to 12.5% of its original intensity? I am confused on what number to start with

*August 27, 2013 by Colby*

**Physics**

Can someone give me an example of how to use this formula: 15.Obtain three half-life (T0.5) times from the graph. Average them.(T0.5)av. Or is there a web site i can go to that shows all steps to using pennies for radioactive decay experiment? .

*November 15, 2007 by Will*

**Elem. ED.**

Art and math are being integrated when students: 1. draw more than 1 picture on a page. 2. use rectangular paint pots. 3. identify geometric shapes when composing a picture. 4. insist on using the same materials as their peers. Is the 3rd answer correct? "identifying geometric...

*April 9, 2007 by Keisha*

**chem**

19. A radioactive nucleus decays to yield a bismuth-211 nucleus and an alpha particle. What was the identity of the original nucleus? Show the nuclear equation that leads you to this answer.

*November 21, 2014 by Zak*

**Science**

How much of a radioactive material with a half-life of 12,000 years is left after 36,000 years of decay?

*April 17, 2009 by Angie*

**chm**

An unknown radioactive substance has a half-life of 3.20 . If 34.8 of the substance is currently present, what mass was present 8.00 hours ago?

*February 10, 2012 by cp*

**Exponential decay**

Show that if a radioactive substance has a half life of T, then the corresponding exponential decay function can be written as y=y0e^kt

*September 4, 2014 by Adrianna*

**Chemistry**

If a 40 gram sample of radioactive isotope was present at 4pm, but a 5 gram sample remained at 4:30 pm, what is the half-life in minutes?

*December 15, 2014 by Jason*

**Science**

If 15% of the radioactive material decays in 5 days, what would be the percentage of amount of original material left after 25 days?

*June 4, 2015 by Anonymous*

**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.

*September 3, 2015 by Ken*

**Algebra**

If 18g of a radioactive substance are present initially and 8 yr later only 9 g remain, how much of the substance will be present after 20 yr?

*September 22, 2015 by Sasha*

**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?

*August 1, 2012 by Mira*