Fluorine20 has a halflife of 11.0 s. If a sample initially contains 49.0 μg of this isotope, how much remains after 66.0 s ?
33,042 results
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

Gen Chem
Neptunium239 has a halflife of 2.35 days. How many days must elapse for a sample of 239Np 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

Chemistry
Nitrogen dioxide decomposes at 300°C via a secondorder process to produce nitrogen 14) monoxide and oxygen according to the following chemical equation. 2 NO2(g) → 2 NO(g) + O2(g). A sample of NO2(g) is initially placed in a 2.50L reaction vessel at

Chemistry
Upon decomposition, one sample of magnesium fluoride produced 1.65kg of magnesium and 2.58kg of fluorine. A second sample produced 1.38kg of magnesium. How much fluorine (in grams) did the second sample produce?

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?

chemistry
Fluorine20 has a halflife of 11.0 s. If a sample initially contains 49.0 μg of this isotope, how much remains after 66.0 s ?

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

chemistry
There are 5g of 131I left after 40.35 days. How many grams were in the original sample if its halflife is 8.07 days? What is the half life of a radioisotope if you started with 1 gram and 0.250 grams is left after 6 days? im not looking for a free answer,

Science
The half life of an element x is 5days. If we have 5g of x initially, what is the mass of x after

Physics
Gold198 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 au198 remaining to time in days. What percentage of a sample of Au198 would reamin after 1 day, 1 week? Given the

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?

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

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

College Algebra
Use a calculator to help solve the problem. One isotope of holmium, 162Ho, has a half life of 22 minutes. The halflife of a second isotope, 164Ho, is 37 minutes. Starting with a sample containing equal amounts, find the ratio of the amounts of 162Ho to

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

math
Iodine131 is a radioactive isotope used in the treatment of thyroid conditions. It has a halflife of 8 days. Halflife is the amount of time it takes for half of the substance to decay (or disappear). If a patient is given 20 mg of iodine131, how much

college algebra
One isotope of holmium, 162Ho, has a half life of 22 minutes. The halflife of a second isotope, 164Ho, is 37 minutes. Starting with a sample containing equal amounts, find the ratio of the amounts of 162Ho to 164Ho after one hour. Rounded to three decimal

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

Chemistry
The half life of U238 is 4.5 x 10^9 yr. A sample of rock of 1.6 g produces 29 dis/sec. Assuming all radioactivity is due to U238 find percent by mass of U 238. I have tried ln(t)/ln(0)= kt and still cannot get the answer What I get is A) 4.5x10^9

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

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

chemistry
the halflife of polonium218 is 3.0 minutes. what percentage of the original sample remains after 4 halflives?

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

chem
Cesium137 has a half life of 30.0 years. If initially there are 8.0 kg of cesium137 present in a sample, how many kg will remain after 60.0 years?

chemistry
a radioactive material is undergoing nuclear decay. After 40 minutes, 25% of the sample remains. What is the halflife of the sample

Ap chemistry
a sample of radioactive iodine (half life=3 days) originally weighed 10 g, but now weighs 0.625 g. How old is the sample?

chemistryplease check
1. For the 1st order reaction whose rate law constant, k, is 1.5x103s1, t½ is a. 7.7 minutes *** b. 462 minutes c. 6.5 minutes d. 4.5 minutes 2. If the halflife of a 1st order reaction is 137 minutes, k= a. 8.43x105s1 b. 11,900 s1 c. 5.06x103s1

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

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
Cobalt60, which undergoes beta decay, has a halflife of 5.26 yr. How many beta particles are emitted in 190s by a 3.10mg sample of Co60? What is the activity of the sample in Bq?

chemistry
Find the number of disintegrations per minute emitted by 1.1 mol of 232Th in 1 min. The halflife of 232Th is 1.4 x 1010 year I was able to do this with the following technique: 1.1 x 6.022 x10^23 =6.62x10^23 1.4x10^10=7.358x10^15 minutes I think then it

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
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

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
Upon decomposition, one sample of magnesium fluoride produced 1.65kg of magnesium and 2.58kg of fluorine. A second sample produce 1.38kg of magnesium. How much fluorine (in grams) did the second sample produce?

Chemistry
Upon decomposition, one sample of magnesium fluoride produced 1.65kg of magnesium and 2.58kg of fluorine. A second sample produced 1.50 kg of magnesium. How much fluorine (in grams) did the second sample produce?

Physics (Inside the atom)
A sample of radioactive isotope I is to be used for medical diagnosis of the kidneys. The isotope has a halflife of 8.0 days, and the sample is required to have an activity of 8 x 10^5 per second at the time it is given to the patient. Calculate the mass

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

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
Po210 Ia an alpha emitter with a halflife of 138 days. how many grams of Po210 remain after 552 days if the sample initially contained 5.80g of Po210?

science
a radioisotope, Iodine131, has a half life of 8.1 days. explain what this means. draw a particle diagram for a sample 12 particles of I131 initially after 8.1 days and after16.2 days.

Physcis 30
Q1) If there are 100 radioactive atoms with a halflife of 30 seconds, how many radioactive atoms will remain after one halflife (30 seconds)? How many will remain after two halflives (60 seconds)? Three halflives? So basically, after 30 seconds it will

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

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)

physics lab
For an unknown sample of the experiment, students measure 1602 counts when they first receive their sample and 1317 counts 3.5 minutes later. Calculate the halflife t12 of their sample.

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

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

physics
Suppose 32000 radioactive nuclei are in a sample. About how many remain after two days if the halflife is 22 hrs? What is the initial activity of the sample in decays per minute?

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?

chemistry
A sample of 131 I was purified and then analyzed for iodine content. It was found that the sample was 99.8% pure. 25 hours later the sample was tested again and it was found that the sample was now just 78.2% pure. What is the half  life of 131 I?

physics
The halflife of Th(227) is 18.72 days. It decays by alfa emission to Ra(223), an alfa emitter whose halflife 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

pre calc
You have a sample of a certain radioactive substance. After two days, thirty percent of the sample has decayed. What is the halflife of the material and how much will have decayed after a week?

pre calc
You have a sample of a certain radioactive substance. After two days, thirty percent of the sample has decayed. What is the halflife of the material and how much will have decayed after a week?

Chemistry
Cobalt60, which undergoes beta decay, has a halflife of 5.26 yr. How many beta particles are emitted in 190s by a 3.10mg sample of Co60? What is the activity of the sample in Bq?

Chemistry
Cobalt60, which undergoes beta decay, has a halflife of 5.26 yr. How many beta particles are emitted in 190s by a 3.10mg sample of Co60? What is the activity of the sample in Bq?

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 halflife in minutes?

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.

Chemistry
All isotopes of technetium are radioactive, but they have widely varying halflives. If an 800.0 g sample of technetium99 decays to 100.0 g of technetium99 in 639,000 y, what is its half life

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
fluorine18 half life of 110 min if 100mg was shipped at 8:00 am how many mg are still active at 1;30 pm same day

physics
Radon 86222Rn is a radioactive gas with a halflife of 3.82 d. If there are initially 400 decays/s in a sample, how many radon nuclei are left after 2 d ? Please help, I don't understand how to do this.

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
Upon decomposition, one sample of magnesium fluoride produced 1.66kg of magnesium and 2.56kg of fluorine. A second sample produced 1.29kg of magnesium. How much fluorine (in grams) did the second sample produce?

College Chemistry
Upon decomposition, one sample of magnesium fluoride produced 1.66kg of magnesium and 2.56kg of fluorine. A second sample produced 1.25kg of magnesium.How much fluorine (in grams) did the second sample produce?

Chemistry
Upon decomposition, one sample of magnesium fluoride produced 1.65kg of magnesium and 2.58kg of fluorine. A second sample produced 1.38kg of magnesium. How much fluorine (in grams) did the second sample produce?

Chemistry
one sample of magnesium fluoride produced 1.65kg of magnesium and 2.58kg of fluorine. A second sample produced 1.31kg of magnesium. How much fluorine (in grams) did the second sample produce?

modern physics
A radioisotope P has a halflife of 3 s. At t = 0, a given sample of this isotope contains 8000 atoms. Calculate (i) its decay constant, (ii) average life, (iii) the time t1 when 1000 atoms of the isotope P remain in the sample, and (iv) number of decays

Chemistry
Nitrogen dioxide decomposes at 300°C via a secondorder process to produce nitrogen 14) monoxide and oxygen according to the following chemical equation. 2 NO2(g) → 2 NO(g) + O2(g). A sample of NO2(g) is initially placed in a 2.50L reaction vessel at

chemistry
How do you find the halflife 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 2.0g sample of phosphous32 contains only 0.25g of

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.

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

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?

Chem
Upon decomposition, one sample of magnesium fluoride produced 1.65 of magnesium and 2.57 of fluorine. A second sample produced 1.38 of magnesium. How much fluorine (in grams) did the second sample produce?

Chemistry
Upon decomposition, one sample of magnesium fluoride produced 1.64 kg of magnesium and 2.57 kg of fluorine. A second sample produced 1.38 kg of magnesium. How much fluorine (in grams) did the second sample produce?

chemistry
Upon decomposition, one sample of magnesium fluoride produced 1.65 kg{\rm kg} of magnesium and 2.58 kg{\rm kg} of fluorine. A second sample produced 1.50 kg{\rm kg} of magnesium. How much fluorine (in grams) did the second sample produce?

chem
The halflife of the Nobelium isotope No^257 is about 23 seconds. 644 seconds (or 28 halflife periods) after the isotope was released there were 20 grams remaining. The number of grans of No^257 after h half life periods is M= 20 * (1/2)^h where h = 0

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?

physics
A building has become accidentally contaminated with radioactivity. THe longest lived material in the building is strontium90 (atomic mass of 90 Sr 38 is 89.9077). If the building initially contained 5.0kg of this subtstance and the safe level is less

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

Physics (I have a test tmrw)
The halflife of Strontium90 is 28 a. If 60 g of this isotope is currently in a sample of soil, estimate the amount in the same sample 84 a later. So I did a=60g(1/2)^84/28 But I don't know if thats correct. Thank for your help!

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?

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.

algebra 2
element x has a half life of 90 seconds. How much of a 100 gram sample of element x is left after half an hour

halflife
1. The halflife of a firstorder reaction is 9.89 minutes. How many minutes will have elapsed after 27 halflives? My answer is 267.03. 2. The halflife of a secondorder reaction is 2.508 days. How many days will have elapsed after 8 halflives? My

calculus
The halflife of a certain radioactive sub stance is 8 hrs. There are 5 grams present initially. Which of the following gives the best approximation when there will be 1 gram remaining?

nuclear
Calculate the age of a plant sample that shows about oneeighth of the carbon 14 of a living sample. The halflife of carbon14 is about 5760 a. Help please...

nuclear physics
Calculate the age of a plant sample that shows about oneeighth of the carbon 14 of a living sample. The halflife of carbon 14 is about 5760a How do you do this?

Chemistry
Cobalt60, which undergoes beta decay, has a halflife of 5.26 yr. How many beta particles are emitted in 190s by a 3.10mg sample of Co60? What is the activity of the sample in Bq?

physical science
A sample of phosphorus32 has a halflife of 14.28 days. If 55 g of this radioisotope remain unchanged after approximately 57 days, what was the mass of the original sample? help please, im confused.

Chem
The only stable isotope of fluorine is fluorine19. Predict possible modes of decay for fluorine21, fluorine18, and fluorine17. Would it just be alphaparticle production, betaparticle production, gammaray production, and positron production for all

physics
How do I do this ? Calculate the age of a plant sample that shows about oneeigth of the carbon 14 of a living sample. The halflife of carbon14 is about 5760a I don't have the notes on how to do this one... Help

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?

Chemistry
To an initially evacuated 50.0L container maintained at 155C were added 3.20g of gaseous xenon and 4.00g of gaseous fluorine. A spark was used to initiate reaction between xenon and fluorine, and gaseous xenon hexafluoride was the sole reaction product.

Physics ...
116In nuclei are produced at the rate of 10 s1. Calculate the maximum number of 116In nuclei (number in equilibrium) in the sample if the halflife of 116In is 54 m. So far I have come up with ... The half life = 54m x 60 s1 = 3.24 x 103 s1 (In2) / λ =

Chemistry
Fluorine18, which has 1/2 life of 110 minutes, is used in PET scans. If 100 mg of fluorine18 is shipped @8AM, how many milligrams of the radioisotope are still active if the sample arrives at the lab at 1:30 pm?

Chemistry
Upon decomposition, one sample of Magnesium Fluoride produced 1.65 kg of magnesium and 2.57 kg of fluorine. A second sample produces 1.33 kg of magnesium. How much fluorine (in grams) did the second sample produce?

Chemistry
The halflife of iodine 131 is 16 days. If you start with 100 gram sample, how many halflives have past when you have less than a gram left?

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?

linear/exponential
This question involves the halflife formula. In this exercise, we are to give a halflife for an exponentially decaying quantity. Need answer to the following: The halflife of a drug in the bloodstream is 4 hours. By what factor does the concentration of

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?