Saturday

November 28, 2015
Number of results: 14,562

**Chemistry**

Carbon-14 has a half-life of 5730 y. How much of a 144 g sample of a carbon-14 will remain after 1.719 (times) 10 4y?
*December 11, 2012 by David*

**physical science**

cobalt-60 has a half-life of 5.26 years, how much of a 500 gram sample will be left after 21 years
*February 16, 2013 by sue moore*

**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**

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*

**Chemistry **

The half-life of 232Th is 1.4 * 10^10. Find the number of disintegrations per hour emitted by 1 mil of 232Th in 1 min.
*April 10, 2014 by Nic*

**Chemistry**

The half-life of Th-232 is 1.4E10. Find the number of disintegrations per hour emitted by 1 mol of Th-232.
*April 10, 2014 by Nic*

**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*

**matg**

Cobalt-60 has a half-life of about 5 years. How many grams of a 300 g sample will remain after 20 years? (Points : 1)
*November 6, 2014 by Anonymous*

**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*

**Mathematics**

If a man and a half finishes a job and a half within a day and a half, how many men can finish 3 jobs within 3 days. Please I need help, I am not so sure with my answer of 6. I would like to verify it. THANKS
*June 25, 2013 by xavier*

**Ethics**

Which of the following answers to the meaning of life did Tolstoy hold prior to his change of heart and mind? my answer is A a. Life has no meaning, and we must embrace that fact. b. Life's meaning is to provide comfort for oneself and one's family. c. Life's meaning is to ...
*February 17, 2014 by Annmarie*

**Ethics**

Which of the following answers to the meaning of life did Tolstoy hold prior to his change of heart and mind? my answer is A a. Life has no meaning, and we must embrace that fact. b. Life's meaning is to provide comfort for oneself and one's family. c. Life's meaning is to ...
*February 17, 2014 by Annmarie*

**Chemistry**

How much time in years (assume a 365 day yr) would it take for a 1.6678g sample of 239Np to decay to a mass of 0.8671g if it has a half life of 2.030*10^5s
*May 6, 2011 by Jay*

**Quick Math**

I have a question: How would you solve this? a dozen dozen apples at half a dozen dimes a dozen? In this cause is dozen 12? And half a dozen dimes in 60 cents? So half a dozen dozen is 144/2 so thats 72 correct? yes, half a dozen dozen is 144/2 = 72 but I don't know what that ...
*December 5, 2006 by Gina*

**English III**

In “Lucinda Matlock,” what is the title character's attitude toward life? A. She thinks life is hard. B. She thinks life is worthwhile. C. She thinks life is boring. This one has to be C because she is happy all the time.
*June 10, 2012 by Anonymous*

**Physics help**

how would you investigate if the half life of water dripping from a burette is constant? I know the method but what equation and principle would ya'll use?
*February 17, 2008 by Daggeron*

**Chemistry**

HCO2H(g) ¨ CO2(g) + H2(g) The half-life for the reaction at 550 ‹C is 24 seconds. How many seconds does it take for the formic acid concentration to decrease by 75%?
*November 11, 2009 by Anonymous*

**chemistry**

What is the half-life of a compound if 69 percent of a given sample of the compound decomposes in 59 min? Assume first-order kinetics.
*January 31, 2010 by danielle*

**chemistry**

For the reaction A to products}, the following data were obtained: t=0 s, A}]=0.715 M; 22 s, 0.605 M; 74 s, 0.345 M; 132 s, 0.055 M. What is the half-life of the reaction?
*February 28, 2010 by joe*

**chemistry**

For the reaction A to products}, the following data were obtained: t=0 s, A}]=0.715 M; 22 s, 0.605 M; 74 s, 0.345 M; 132 s, 0.055 M. What is the half-life of the reaction?
*February 28, 2010 by joe*

**chemistry**

For the reaction A to products}, the following data were obtained: t=0 s, A}]=0.715 M; 22 s, 0.605 M; 74 s, 0.345 M; 132 s, 0.055 M. What is the half-life of the reaction?
*February 28, 2010 by joe*

**Chemistry**

half life of tritium is 12.5 years. how much will remain after 100 years if you started wit 256 grams?
*October 14, 2010 by Anonymous*

**chemistry**

the half-life of radon-222 is 3.823 days. what was the original mass if 0.050g remains after 7.646 days?
*October 21, 2010 by Anonymous*

**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 thats wrong...
*November 18, 2010 by jess*

**Calculus**

suppose that a population is dying with a half life of of 43years. The initial size is 1600. Find the 1 year DTDS for this population
*February 6, 2011 by Anonymous*

**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? .
*April 7, 2011 by sandy*

**College Math**

Only 43% ofthe carbon-14 in an artifact remains. How old is the artifact? Would the answer be less than the half life?
*February 19, 2012 by Angel*

**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*

**Algebra 2**

half life carbon -14 is 5,730 years. If you start out 50 grams, how long will it take until it reaches 2 grams?
*May 20, 2012 by chels*

**Science**

A certain isotope has a half-life of 12 hrs. How long will it take for 100 ƒİgr to decay into only 25 ƒİgr?
*July 15, 2012 by Haley*

**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*

**Calculus**

The half-life of Radium-226 is 1590 years. If a sample contains 100 mg, how many mg will remain after 4000 years?
*November 16, 2012 by Anonymous *

**Math**

assume the substance has a half-life of 11 years and the initial amount is 126 grams. How much remains at the end of 8 years?
*January 25, 2013 by Jackie*

**chemistry**

If something originally contained 32.0 g of Po-210, which has a half-life of 10.5 minutes, and was now 73.5 minutes old, how many grams would be left?
*May 13, 2013 by Mary *

**science**

Please help me with this question.... The isotope caesium-137, which has a half-life of 30 years, is a product of nuclear power plants. How long will it take for the amount of this isotope in a sample of caesium to decay to one-sixteenth of its original amount? k = 0.693/t1/2...
*February 5, 2007 by Mary*

**English**

Especially when the game is called life. There can be a champion in each of us, If we live as a winner, If we live as a member of the team, If we live with a hopeful spirit, For life. ----------------------------- This is a poem. What is the meaning of the last expression "...
*December 11, 2014 by rfvv*

**math**

an extremely volatile substance, Ofnetite, has a half-life of 25 minutes. Find the percentage decrease of this substance in the first two hours.
*November 8, 2009 by katy*

**Chemistry 212**

the half life of F18 is 2.089x10^-4yrs. How long would it take (in days) for F18 to decrease to 78.71% of its initial amount?
*May 10, 2010 by pookie*

**Chemistry-help please!**

The half-life of Xe-133 is 126 hours. Starting with 250. mg, after 500 hours around how many mg remain? A. 63 B. 16 C. 32 D. 125
*May 23, 2010 by Charleze*

**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*

**chemistry**

caffeine has a half-life of 4.6 hours in the human body.. How long would it take 125 milligrams tritium to decay to 22 milligrams?
*April 11, 2011 by cam*

**Chemistry **

carbon 14 has a half life of 5715 years. If you start with a 5 gram sample of 14C, what mass is left after 15,000 years?
*April 24, 2012 by Mima*

**Chemistry**

A fossil is found to have a C-14 level of 86% compared to living organisms. How old is the fossil?, (the half life of C14 is 5730 years).
*April 27, 2012 by Mima*

**Chemistry**

Carbon-14 has a half-life of 5730 years In a plant fossil you find that the 14 C has decayed to 1/8 of the original amount how long ago was this plant
*September 24, 2012 by Shay*

**Science chemistry**

It takes 1 hour and 17 min. for a 1.000gsample of a certain isotope to decay to 0.121g. What is the half-life of this isotope? plssss helpp
*September 24, 2012 by Shay*

**chemistry**

It takes 1 hour and 17 min. for a 1.000g sample of a certain isotope to decay to 0.121g. What is the half-life of this isotope? plssss helpp
*September 24, 2012 by Shay*

**earth science**

if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days
*November 29, 2012 by lan*

**earth science**

if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days
*November 29, 2012 by lan*

**earth science**

if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days
*November 29, 2012 by lan*

**chemistry**

Carbon-14 has a half-life of 5730 . In a plant fossil, you find that the has decayed to 1/32.0 of the original amount. How long ago was this plant alive?
*December 3, 2012 by niles28*

**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*

**Biology**

The half-life of Carbon-14 is 5730 years. What is the age of a fossil containing 1/16 the amount of Carbon-14 of living organisms? Explain your calculation.
*December 9, 2012 by Melissa*

**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
*September 19, 2013 by Anonymous*

**Math**

Suppose you have a cache of radium, which has a half-life of approximately 1590 years. How long would you have to wait for 1/5 of it to disappear?
*March 26, 2015 by Will*

**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*

**College Chemistry**

How much time in years (assume a 365 day yr) would it take for a 1.6678g sample of 239Np to decay to a mass of 0.8671g if it has a half life of 2.030*10^5s
*May 5, 2011 by Jude*

**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*

**Life of a Soldier**

Could you please give me some points, details explaining life of an average canadain soldier. Ive jotted down a few, but if you could give me some more, that would help me loads. Didn't get many hours of sleep Poor Living Conditions Had to stand out in the trenches daily, had ...
*October 12, 2011 by Anonymous*

**chemistry 2**

A voltaic cell is constructed with an Ag/Ag+ half-cell and a Pb/Pb2+ half-cell. Measurement shows that thesilver electrode is positive. -Write balanced half-reactions and the overall spontaneous reaction.
*April 27, 2012 by anonymous*

**physics**

A baseball leaves a pitcher's hand horizontally at a speed of 115 km/h. The distance to the batter is 18.3 m. (Ignore the effect of air resistance.) (a) How long does the ball take to travel the first half of that distance? (b) The second half? (c) How far does the ball fall ...
*October 7, 2012 by tatiana*

**physics**

A baseball leaves a pitcher's hand horizontally at a speed of 115 km/h. The distance to the batter is 18.3 m. (Ignore the effect of air resistance.) (a) How long does the ball take to travel the first half of that distance? (b) The second half? (c) How far does the ball fall ...
*September 19, 2013 by kristy*

**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*

**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?
*December 21, 2010 by Bree*

**math**

how to compute this problem? a certain element has a half life of 12 years. if there were 1000 milligrams originally, find the remaining amount after 20 years?
*January 12, 2011 by diane*

**chemistry**

the mass of cobalt-60 in a sample is found to have decreased from 0.800g to 0.200g in a period of 10.5 years. from this info calculate the half-life of cobalt-60
*April 6, 2011 by shaleena*

**chemistry**

the mass of cobalt-60 in a sample is found to have decreased from 0.800g to 0.200g in a period of 10.5 years. from this info calculate the half-life of cobalt-60
*April 6, 2011 by shaleena*

**chemistry**

a sample of a radioisotope had a mass of 100.0 grams. After exactly 24 days, 6.25 grams remained. The half life of the isotope is _________
*June 3, 2011 by rick*

**chem**

Cobalt-60, which undergoes beta decay, has a half-life of 5.26 yr. (a) How many beta particles are emitted in 47.0 s by a 2.39-mg sample of 60Co? i got 2.44e19 but thast wrong
*September 12, 2012 by sara*

**math**

3. The half-life of a certain drug in the human body is 8 hours how long it would take for a dose of this drug to decay to 0.1% of its initial level?
*November 12, 2013 by hannah*

**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 half-life of the reaction, at 34 degrees celsius and Ppan=13.2 torr, is 164.0hr. Calculate the rate constant for the reaction. confused on what to do here
*February 10, 2015 by mar*

**Physic**

A newly prepared radioisotope has activity 3.7x10^11 Bq. After 4 hours, its activity is reduced to 2.96x10^11.calculate a) decay constant b) its half life
*April 14, 2015 by Aboi*

**Physic**

A newly prepared radioisotope has activity 3.7x10^11 Bq. After 4 hours, its activity is reduced to 2.96x10^11.calculate a) decay constant b) its half life
*April 14, 2015 by Aboi*

**Physic**

A newly prepared radioisotope has activity 3.7x10^11 Bq. After 4 hours, its activity is reduced to 2.96x10^11.calculate a) decay constant b) its half life
*April 16, 2015 by Aboi*

**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*

**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*

**Physics**

Determine the activity of 1.11 g of 88Ra226 (a) in disintegrations per second (Bq) (b) and in Curies (Ci). The half-life is 1600 yr (1 yr = 3.156 x 10^7 s). 1 Ci is equal to 3.7 x 10^10 Bq. I keep getting the wrong answer and use the equation H=kNo
*July 29, 2012 by Beth*

**Chemistry**

In solution, hypochlorite ion is known to decompose with a second-order rate law. If [ClO-]0 = 0.0570 M and k = 2.06x10-4 M-1·min-1, calculate the half-life for this reaction 2ClO- 2Cl- + O2.
*September 6, 2012 by Amber*

**chemistry**

Radioactive waste is difficult to dispose of due to the long time periods needed before the radiation effectively disappears. The US protocol is to store the waste for 10 half-lives of the material after which the waste is no longer considered radioactive. After this time, ...
*February 14, 2015 by danny*

**chemistry math**

linen scrolls contain 80.9% of Carbon-14. how old are the scrolls if the half-life for deacy is 5.73X10^3?? plz tell me what type of equation to use.
*October 15, 2008 by ronny*

**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*

**chemistry**

Consider the first order reaction A --> products where 25% of A disappears in 24 seconds. What is the half life of this reaction? ...i thought it would just be doubled but it isn't. i'd appreciate an explanation.
*April 29, 2010 by omar*

**Alg2**

A piece of wood discovered in an archaeological dig was found to have lost 62% of it's carbon-14. Carbon-14 has a half-life of 5630 years. Determine it's age.
*June 1, 2010 by Cal*

**Calculus **

Radius decays at a rate of that is proportional to its mass, and has a half-life of 1590 years. If 20 g of radium is present initially, how long will it take for 90% of this mass to decay?
*June 17, 2010 by Anonymous*

**Math**

The half-life of 234U, uranium-234, is 2.52 105 yr. If 97.7% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed? ? yr
*July 15, 2011 by Lee Ann*

**algebra**

The half-life of 234U, uranium-234, is 2.52 105 yr. If 97.7% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed
*July 18, 2011 by sissy*

**algebra**

The half-life of 234U, uranium-234, is 2.52 105 yr. If 97.7% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?
*July 20, 2011 by Anonymous*

**math**

The half-life of 234U, uranium-234, is 2.52 105 yr. If 97.4% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?
*October 22, 2011 by lady*

**algebra**

The half-life of plutonium-234 is 9 hours. If 40 milligrams is present now, how much will be present in 4 days? (Round your answer to three decimal places.)
*November 20, 2011 by meghan*

**algebra**

The half-life of 234U, uranium-234, is 2.52 105 yr. If 98.4% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?
*December 16, 2011 by lance*

**math**

The half-life of 234U, uranium-234, is 2.52 105 yr. If 98.3% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?
*January 22, 2012 by Anonymous*

**algebra**

The half-life of 234U, uranium-234, is 2.52 105 yr. If 97.7% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?
*January 28, 2012 by Anonymous*

**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*