The halflife of lead is 22 years. How long will it take for a sample of this substance to decay to 80% of its original amount
66,229 results
math
An element has a halflife of 30 years. If 1.0 mg of this element decays over a period of 90 years, how many mg of this element would remain? Begin amount is 1.0 elapsed time is 90y half life 30 years n=9/30 n=3 90/2^2 90/8 = 11.25mg thinking it's wrong

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

Chemistry(difficult)
A moon rock collected by a U.S. Apollo mission is estimated to be 3.70 billion years old by uranium/lead dating. Assuming that the rock did not contain any lead when it was formed, what is the current mass of 206Pb per 1.185 g of 238U in the rock? The

Calc
A sample of a radioactive substance decayed to 93.5% of its original amount after a year. a) What is the halflife of the substance? ? years (b) How long would it take the sample to decay to 10% of its original amount? ? years

Chemistry
Gallium65, a radioactive isotope of gallium, decays by first orderkinetics. The halflife of this isotope is 15.2 min. How long would it take for 7/8 of a sample of this isotope to decay? 15.2 min 30.4 min 45.6 min 48.0 min I'm not sure how to do this. I

Pre Calculus
Radium221 has a halflife of 30 s. How long will it take for 95% of a sample to decay

Chemistry
the halflife of cobalt60 is 5.20 years.. how many milligrams of a 2.000mg sample remains after 6.55 years

maths
The halflife of lead is 22 years. How long will it take for a sample of this substance to decay to 80% of its original amount

Chemistry
A pure sample of tritium, 3H, was prepared and sealed in a container for a number of years. Tritium undergoes â decay with a halflife of 12.32 years. How long has the container been sealed if analysis of the contents shows there are 5.25 mol of 3H and

chemistry
a)indium115 has a half life of 4.5 hours. if you start with a 12.0mg sample of indium115, how much will remain after 13.5 hours? b)how much of a 3.50mg smaple of nickel63 will remain after 368 years? the halflife of nickel63 is 92 years?

Math  Exponential Decay
Radium decays exponentially. Its halflife is 1,690 years. How long will it take for a 50gram sample of radium to be reduced to 5 grams? 1/2P = Pe^(1690k) (ln1/2)/(1690) = k 4 x 10^4 = k 5 = 50e^kt ln0.1 = kt ln0.1/k = t 5,630 years = t ...but

chemistry
A 1.00g sample of carbon from a modern source gave 15.3 disintegrations per minute. A sample of carbon from an “old” source gave 920 disintegrations per hour. What is the age of the “old” sample of carbon? The halflife of carbon14 is 5.73×103

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

science
The halflife 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

Precalculus
Trtitum, a radioactive isotope of hydrogen, has a halflife of 12.4 years. Of an into tail amount sample of 50 grams, how much will remain after 10 years?

College algerba
The halflife of a certain radioactive element is about 1500 years. After 2800 years, what percentage P of a sample of this element remains?

chemistry
How long will it take for 25% of the C14 atoms in a sample of C14 to decay? The halflife for the radioactive decay of C14 is 5730 years. If a sample of C14 initially contains 1.1 mmol of C14 , how many millimoles will be left after 2275 years?

halflife
the half life of isotope X is 2.0 years how many years would it take for 4.0 mg sample of X to decay and have .50 mg of it remain?

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

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 100gram sample of the radioactive

Chem 2
The halflife for the radioactive decay of U238 is 4.5 billion years and is independent of initial concentration. a) How long will it take for 10% of the U238 atoms in a sample of U 238 to decay? b)If a sample of U238 initially contained 1.9×1018

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

Ap chemistry
if a 84g sample of thorium decays with a 10 minute half life, how much would the sample weight in a half hour?

chemistry
A moon rock collected by a U.S. Apollo mission is estimated to be 4.50 billion years old by uranium/lead dating. Assuming that the rock did not contain any lead when it was formed, what is the current mass of 206Pb per 1.150 g of 238U in the rock? The

science
the half life of tritium is 12.5 years. How much of a 1 g sample will remain after 25 years

Math
The halflife of strontium90 is 28 years. How long will it take a 60 mg sample to decay to a mass of 15 mg?

word problem
The half life of cesium137 is 30 years. Suppose we have a 10g sample. a)Find a function that models the mass remaining after t years. b)How much of the sample will remain after 80 years? c)After how long will only 2 g of the sample remain? Thanks (a)

math
the half life of thorium 229 is 7340 years. how long will it take for sample of this substance to decay to 20% of its original amount

chemistry
Strontium90 has halflife of 28 years. if a 1.00mg sample was stored for 112 years. what mass of Sr90 would remain?

science
Carbon14 has a halflife of approximately 5,730 years. How many halflives have occurred in a sample that contains 50 percent of the original amount of the parent isotope?

College algebra
The radioactive element has a halflife of about 28 years and sometimes contaminates the soil. After 47 years, what percentage of a sample of the elements remain?

Calculus
The halflife of Radium226 is 1590 years. If a sample contains 100 mg, how many mg will remain after 4000 years?

physical science
cobalt60 has a halflife of 5.26 years, how much of a 500 gram sample will be left after 21 years

HalfLife
Uranium238 decays to Lead206. The half life of Uranium238 is 4.5 billion years. If you have a 100 g sample. How much sample will you have after 2 half lifes?

Physic
A sample of radium weighs 1000g.How long will it take to decay to 125g if its halflife is 1620 years?

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?

Physics
The isotope carbon14, 146C, is radioactive and has a halflife of 5730 years. If you start with a sample of 1000 carbon14 nuclei, how many will still be around in 22920 years? I got 62.5 atoms, am I correct?? Thank you!!

chemistry
an original sample of K40 has a mass of 25.00 grams. After 3.9x 10 to the ninth years, 3.125 grams of the original sample remains unchanged. What is the halflife ok K40 in minutes? Is it 6.8328 x 10 to the 14th

chemistry
The isotype 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 isotype in a sample of caesium to decay to onesixteenth of its original amount? first half life 1/2 second 1/4

Chemistry (Dr.Bob222)
The halflife of P32 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

chemistry
Strontium90 decays through the emission of beta particles. It has a halflife of 29 years. How long does it take for 80% of a sample of strontium90 to decay? Show process of how you got this

Chemistry *URGENT*
URGENT help! 3. A rock sample was dated using potassium40, 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 uranium238. It that lava

Biology
The halflife of carbon14 is 5,700 years. If a sample originally had 26 g of carbon14, how much would it contain after 22,800 years?

Calculus
The half life of a certain radioactive substance is 10 years. How long will it take for 18 gms of the substance to decay to 6 gms? A. 6 ln 10 years B. 10 ln 6 years C. 10 (ln 3)/(ln 6) years D. 18 ln 10 years E. 10 (ln 3)/(ln 2) years

Math
Plutonium239 has a halflife of 24 000 years. What percent of plutonium239 remains after 10 000 years? (Answer=74.9%) AND After 30 hours, a sample of Plutonium 243 (PU^ 243) has decayed to 4 ^ 1/3 of its original mass. What is the half life of PU^ 243.

Science
An element has a halflife of 30 years. If 1.0 mg of this element decays over a period of 90 years, how many mg of this element would remain? Begin amount is 1.0 elapsed time is 90y half life 30 years n=9/30 n=3 90/2^2 90/8 = 11.25mg thinking it's wrong

chemistry
90Sr is one of the harmful radionuclides resulting from nuclear fission explosions. It decays by a firstorder process with a halflife of 28 years. How many years would it take for 99.99% of a given sample released in the atmosphere to disintegrate?

Chem 3A
please help me with this chemistry problem. HalfLife A radium226 sample initially contains 0.112 mol. How much radium226 is left in the sample after 6400 years? The halflife of radium226 is 1600 years.

Physics
Half life of radium is 44 years.The sample will reduce to 50% of its orignal value ater how many years?

Algebra
An isotope has a halflife of 97 years. how much of a 19gram sample is left after 150 years?

matg
Cobalt60 has a halflife of about 5 years. How many grams of a 300 g sample will remain after 20 years? (Points : 1)

SCIENCE
We did a radioactive decay and half life lab with m&ms and I do not understand these conclusion questions: 1. how many half lives would it take for 500 nuclei to decay to 6.25% of the original number of nuclei? My ans: 3125? do not think that's right! 2.

chemistry
The halflife of stronitum90 is 28 years. How many grams of this nuclide in a 4.00g sample will remain after 112 years?

Science
If a 20 gram sample of a radioactive substance has a halflife of 6000 years, how many grams would be present after 18000 years?

Science HELP 2nd question
A sample originally contained 2.5 g of rubidium 87 now contains 1.25 g. The half life of rubidium  87 is 6 x 10 ( to the 10th) years. How old is the sample? Is this possible? why or why not?

Chemistry
Uranium238 has half life of 4.51 * 10^9 years Uranium234 has half life of 2.48 * 10^5 years Thorium230 has half life of 8.0 * 10^4 years Radium226 has half life of 1.62 * 10^3 years Lead210 has half life of 20.4 years. The rate constant for the decay

Chemistry please help!
A Cesium 137 sample has a measured radioactivity of 50 microcuries.Cesium 137 has a halflife of 30 years. How long will it take this sample to be reduced to a residual radioactivity of 6.25 microcuries? Is there a formula to calculate half life?

Chemistry
The isotope caesium137, which has a half life of 30 years, is a product of neuclear 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. Explain answer 30 years 1/2 60

Chemistry
The halflife of C14 is 5700 years. If it took seven half lives for a sample of C14 to decay completely, how many years would have gone by?

chemistry
What percent of the original sample of strontium90 (halflife = 28.9 years) will remain after the following time periods?after 18 years? after 47.5 years? after 1008 years?

Chemistry
If 25.0 g of a radioactive sample is left after 100.0 years and each halflife is 25 years, how much sample did you start with?

ChemB
The activity of carbon 14 in living tissue is 15.3 disintegrations per minute per gram of carbon. The limit for reliable determination of age is based on carbon 14 is .10 disintegration per min per gram of carbon. Calculate the max age of a sample that can

math
An unknown radioactive element decays into nonradioactive substances. In 100 days the radioactivity of a sample decreases by 64 percent. a)(a) What is the halflife of the element? halflife: b)How long will it take for a sample of 100 mg to decay to 51

chemistry
A 1.00g sample of carbon from a modern source gave 15.3 disintegrations per minute. A sample of carbon from an “old” source gave 920 disintegrations per hour. What is the age of the “old” sample of carbon? The halflife of carbon14 is 5.73×103

chemistry
Some radioactive nuclides have very short halflives, for example, I31 has a halflife of approximately 8 days. Pu234, by comparison has a halflife of 24,000 years. Explain why both of these examples are dangerous, even though their halflives are very

Engineering Math
An unknown radioactive element decays into nonradioactive 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

Physics
Half life of radium is 44 years.The sample will reduce to 50% of its orignal value after how many years?

geology
How old are the oldest meteorites yet studied and what is the minimum age of Earth since Earth is at least as old as the meteorites. We know the oldest meteorites contain equal amounts of uranium 238 and lead 206. Uranium 238 has a half life of 4.5 billion

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 halflife of 704 million years your sample is about 700 million years old and weighs 120 grams

AP Calculus
An Initial amount of 100 grams of Thorium234 decays according to the model: dP/dt=0.02828P (where t is measured in years). a) Find the equation for the amount of Thorium left after t years. b) Determine the halflife of this radioactive isotope c) How

A.P. Chemistry
Thorium232 undergoes alpha decay and has a halflife of 1.4 * 10^10 years. How long will it take for a 1.00mg sample of thorium232 to be reduced to 0.5mg?

Calculus
The halflife of Kryponite123 is 40 years. Suppose we have a 700mg sample. Find the decay k, and the expected amount of Kryptonite left after 30 years. I need help setting this problem up.

science
Im having trouble understanding Half life and what not... 1.If each roll of the dice represents 10,000 years, what is the approximate halflife (in years) of the element Lokium? 2. If each roll of the dice is 10,000 years, what is the approximate halflife

math
one fifth of my life I wanted to become a teacher. 3/25 of my life I was a teenager. 9/25 of my life I was married to my husband. Threefifth of my life my son was born. Fifteen years after that, my daughter was born. Seven years after that I got a divorce

science
Please help me with this question.... The isotope caesium137, which has a halflife 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 onesixteenth of its original

physics
Radioactive nuclei are produced in an irradiated sample at the rate of 10 s1. If the number in the sample builds up to a maximum of 1000, calculate the mean life and the halflife of the radioactive nuclei Using dN / dt = P  λ N dN / dt = 1000n /10/ 1 =

chemistry
The half life of gold197 is 10.6. What fraction of a sample remains after 21.2 years?

science
Cobalt60 has a 30 year halflife. How much of an 80 gram sample would remain after 60 years?

Chemistry
If the half life of Pu239 is 2.4 x 10^4 years, how many years are required for a 20gram sample of plutonium239 to be reduced to a mass of 5 grams?

half life
tritium has a half life of 24.3 years .a sample of 0.1 is produced . will tthe mass of tritium change after 24.3 years

Science/Chemistry
22Na has a halflife of 951 days. How many grams of a 1.00 kg sample would be left after 4 years?

chem
Radioactive substances decay by firstorder kinetics. How many years would be required for a sample containing strontium90 to decrease to 58.32% of its initial activity? The halflife of strontium90 is 2.88e1 years.

physics
The halflife of carbon14 is 5730 years. How much of a 50 g sample of carbon14 is present after 11,460 years?

College Algebra
The halflife of a radioactive material is about 34.6 years. How much of a 1gram sample of the material is left after 30 years?

Calculus
Ba has a halflife of 283.2 hours. How long would it take for the 50 mg of Ba in a sample to decay to 1.0 mg?

chem
A typical dose of a radioactive sample is 27.0 mCi. How long does it take for the activity to reduce to 0.100 mCi? The half life of the sample is 211,000 y.

calculus
a radiotactive isotope lose 1/5 of its atoms in a sample decay after 14 years. find the half life.

physics
If the physical halflife of sulfur35 is 87.1 days, and the biologic halflife in the testicle is 632 days, what is its effective halflife in this organ? I know i have to find the time and then the halflife. But im having trouble finding the time

math
The half life of iodine  131 is 8 days. How long will it take for 7/8 of the sample to decay?

ryancon
The halflife of rubidium87 (natural absorbance 27.83%) is 5.1x10^11 years. What mass of rubidium is present if an average sample decay rate of 35.0 disint./sec is detected? I've already converted years to seconds but not sure what to do after..

chemistry
A radium226 sample initially contains 0.112mol. How much radium226 is left in the sample after 6400 years. The halflife of radium226 is 1600 years.

s103
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?  explain answer 1/16 = 1/2^x

chemistry
With a halflife of 14.3 years, how long will it take for100 g of phosphorus32 to decay to 12.5 mg?

Physics HELP HELP
(for some reason I keep getting this wrong. I put 90 for c, 5.6 for h and 22 for M(x), Then I took the natural log of both sides, but I keep getting it wrong) The mass of a radioactive element at time x is given by the equation below, where c is the

math
You have just isolated a new radioactive element. If you can determine its halflife, 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

Science economic
Cesium 138 has a half life equal to 32.2 minutes. how long will it take for 2/4 of this sample to decay

Math
How long will it take for a 1 g sample of Polonium 210 to lose all but 1/28 of its radioactivity if the halflife is 140 d?

Math
How long will it take for a 1 g sample of Polonium 210 to lose all but 1/28 of its radioactivity if the halflife is 140 d?

Chemistry
After 1.78 years, 1.990 g of a radioisotope remains from a sample that had an original mass of 2.000 g. Calculate the halflife of the isotope.

calculus
Assume a substance has a halflife of 11 years and the initial amount is 144 grams. How much remains at the end of 5 years? How long will it be until only 30 % remains?