# The radioisotope radon-222 has a half-life of 3.8 days. How much of a 65-g sample of radon-222 would be left after approximately 15 days?

34,837 results
1. ## 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?

2. ## Physics

Gold-198 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 au-198 remaining to time in days. What percentage of a sample of Au-198 would reamin after 1 day, 1 week? Given the

A radioisotope has a half-life of 4 days. How much of a 20-gram sample of this radioisotope remains at the end of each time period? 1) 4 days 2) 8 days

4. ## 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

5. ## Physical Science

1. Which equation correctly shows beta decay? (A) 210/82 Pb -> 209/81 Tl + 0/-1 e + y (B) 210/82 Pb -> 209/83 Bi + 0/-1 e + y (C) 210/82 Pb -> 210/83 Tl + 0/-1 e + y (D) 210/82 Pb -> 210/83 Bi + y (E) 210/82 Pb -> 210/83 Bi + 0/-1 e + y 2. The half-life if

6. ## chemistry

There are 5g of 131I left after 40.35 days. How many grams were in the original sample if its half-life 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,

7. ## Gen Chem

Neptunium-239 has a half-life of 2.35 days. How many days must elapse for a sample of 239-Np 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

8. ## 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?

9. ## chemistry

The half-life of radon-222 is about four days. After how many days is the amount of radon-222 equal to one-sixteenth of its original amount? I know the answer is 16,but why? Please steps...thank you!

10. ## chemistry

the half-life of radon-222 is 3.823 days. what was the original mass if 0.050g remains after 7.646 days?

11. ## Chemistry

I've figured out most of it. I'm not sure how to find the percentage ofd the isotope. Define the half life. The half-life of a radioisotope is found to be 4.55 minutes. If the decay follows first order kinetics, what percentage of isotope will remain after

12. ## 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

13. ## science

The iodine-131 nuclide has a half-life of 8.0 days. If you originally have a 257 g sample, after 48 days how much will you have?

14. ## Chemistry

If radon-222 has a half-life of 3.8 days, determine how long it takes for only 1/8 of a sample to remain.

15. ## 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 _________

16. ## 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?

17. ## 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

18. ## sciencemath

Suppose a laboratory has a 31 g sample of polonium-210. The half-life of polonium-210 is about 138 days. How many half-lives of polonium-210 occur in 966 days? How much polonium is in the sample 966 days later?

19. ## Science math

Suppose a laboratory has a 38 g sample of polonium-210. The half-life of polonium-210 is about 138 days. How many half-lives of polonium-210 occur in 1104 days? How much polonium is in the sample 1104 days later?

20. ## 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 that's wrong...

21. ## chemistry

isotope chromium -51 has a half life of 28 days. If the original sample had a mass of 28.0 grams, what mass of chromium -51 sample remains after 84 days?

22. ## Chemistry

The half life of radon 222 is 3.82 days. If the initial mass of a sample of radon 222 is 198.72 grams, how much will remain after 19.25 days?

23. ## chemistry

what is the total mass of Rn-222 remaining in an original 160-mg sample of Rn-222 after 19.1 days?

24. ## chemistry

Examine the information. Element A has a half-life of 10 days. A scientist measures out 200 g of this substance. After 30 days has passed, the scientist reexamines the sample. How much Element A will remain in the sample 100g 12.5g 50g 25g is it d?

25. ## Chemistry

If only 50% of the original amount of a radioisotope remains, half the time has gone by after twice that time there will be nothing left the radioactivity has reached a safe level a half-life has passed

26. ## Chemistry

The radioisotope radon-222 has a half-life of 3.8 days. How much of a 98.4 g sample of radon -222 would be left after approximately 19 days?

27. ## Chemistry

The half-life of radon-222 is 3.82 days. If a sample of gas contains 4.38ug of radon-222, how much will remain in the sample after 15.2 days?

28. ## Algebra

The half-life of radon-222 is 3.8 days. How much of a 300 gram sample is left after 14.8 days?

29. ## 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?

30. ## 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?

31. ## science

A Geiger counter is used to measure the activity of a sample of iodine-131. Based on the data, what is the half-life of iodine-131? A. 16 days B. 8 days C. 4 days D. 12 days

32. ## Math

The half-life of radon-222 is 3.8 days. How much of a 300 gram sample is left after 14.8 days?

33. ## nuclear chem

i need help solving this. Can you guys show me how it's done. Radium-226 decays by alpha emission to radon-222, a noble gas.What volume of pure Radon- 222 at 23oC and 785mmHg could be obtained from 543.0 mg of radium bromide,RaBr2 in a period of 20.2

34. ## Science

Radium has a half-life of 1620 years and decays into radon, which has a half-life of 3.82 days. A 10-gm source of radium is sealed, and the radon produced is pumped off every 24 hours. How many mill curies of radon are pumped off each time?

35. ## Chemistry

Recently, there has been much concern about pollution in the home from radon, a radioactive gas whose elemental molar mass is 222 g/mol. The Environmental Protection Agency say that a level or radon of 3.6 X 10-11 giL of air is unhealthy. At this level,

1. For the 1st order reaction whose rate law constant, k, is 1.5x10-3s-1, t½ is a. 7.7 minutes *** b. 462 minutes c. 6.5 minutes d. 4.5 minutes 2. If the half-life of a 1st order reaction is 137 minutes, k= a. 8.43x10-5s-1 b. 11,900 s-1 c. 5.06x10-3s-1

37. ## half-life

1. The half-life of a first-order reaction is 9.89 minutes. How many minutes will have elapsed after 27 half-lives? My answer is 267.03. 2. The half-life of a second-order reaction is 2.508 days. How many days will have elapsed after 8 half-lives? My

38. ## 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

39. ## Chemistry

The iodine-131 nuclide has a half-life of 8 days. If you originally have 625-g sample, how many grams will you have after 2 months(approximately 64 days)?

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?

41. ## Physical Science

An isotope of radon gas, Rn-222, undergoes decay with a half-life of 3.8 days. How long does it take for the amount of Rn-222 to be decreased to one-sixteenth of the original amount?

42. ## physical science

A sample of phosphorus-32 has a half-life 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.

43. ## chemistry

A 1.50 liter gas sample at 745mm HG and 25 celsius contains 3.55% radon by volume radon-220 is an alpha emitter with a half life of 55.6 seconds. how many alpha particles are emitted in 5 minutes by this sample? I got an answer 1.59x10^19 I started at

44. ## chem

The half-life of is 30.0 days. What fraction of a sample of this isotope will remain after 16.2 days?

45. ## earth science

if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days

46. ## Chemistry

The radioisotope radon-222 has a half-life of 3.8 days. How much of a 65-g sample of radon-222 would be left after approximately 15 days?

47. ## Chemistry

A 1.50- gas sample at 735 and 25.0 contains 5.00 radon-220 by volume. Radon-220 is an alpha-emitter with a half-life of 55.6 . How many alpha particles are emitted by the gas sample in 4.00 minutes?

48. ## chemistry

How do you find the half-life 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 2.0-g sample of phosphous-32 contains only 0.25g of

49. ## Science

Iodine-131 is used I'd diagnosing certain medical problems because of the short half-life, which is 8.02 days. Assume the hospital lab uses for 4.52g of iodine-131 in a month. What mass of this radioisotope remains in patients after 32 days?

50. ## Chemistry

Technetium-99m is an ideal radioisotope for scanning organs because it has a half-life of 6.0 hr and is a pure gamma emitter. Suppose that 200mg were prepared in the technetium generator this morning. How many milligrams would remain after the following

51. ## Chemisty

The activity of a radioisotope is 3000 counts per minute at one time and 2736 counts per minute 48 hours later. What is the half-life of the radioisotope?? a) 831hr b)521hr c)361 hr d)1.44hr

52. ## Chemistry (Dr.Bob222)

The half-life of P-32 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

53. ## chemistry

If a radioisotope's half-life is 2 minutes, after two half-lives there is left?

54. ## Chemistry

The half-life of iron-59 is 45 days. A sample containing this radioactive Isotope has an activity of 200 millicuries (mcl) What will the activity of this sample be after 180 days?

55. ## chemistry

Ba-140 has a half life of 13.0 days. What fraction of a sample will remain after 39 days?

56. ## 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?

57. ## statistics

A random sample of the houses in a particular city is selected and the level of radon gas is measured for each house in the sample. The values collected are given below in parts per million (ppm). Experience has shown that radon gas level is approximately

58. ## Physics (Inside the atom)

A sample of radioactive isotope I is to be used for medical diagnosis of the kidneys. The isotope has a half-life 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

59. ## Chemistry

A radioactive sample contains 3.25 1018 atoms of a nuclide that decays at a rate of 3.4 1013 disintegrations per 26 min. (a) What percentage of the nuclide will have decayed after 159 d? % (b) How many atoms of the nuclide will remain in the sample? atoms

60. ## chemistry

Some radioactive nuclides have very short half-lives, for example, I-31 has a half-life of approximately 8 days. Pu-234, by comparison has a half-life of 24,000 years. Explain why both of these examples are dangerous, even though their half-lives are very

61. ## Physics

An industrial worker accidentally inhaled a radioisotope with an activity of 0.200 kBq. The substance swallowed has a very long effective half-life and therefore the activity will not change significantly during the workers lifetime. Every decay of the

62. ## Chemistry

Radon-222 is a radioactive gas with a half-life of 4 days. Approximately how much of a 40 g sample of radon-222 would remain after 12 days?

63. ## chemistry

the half life radium-222 is 4 days. if a sample of radon-222 undergoes decay for 12 days, how much of the original parent isotope will be left?

64. ## Chemistry

Radon-222 has a half-life of 3.8days. What gram of radio isotopes will remain after 11.4days if you started out with 16 grams of the sample?

65. ## chemistry

how many half-lives of radon-222 have passed in 11.46 days?

66. ## science

a radioisotope, Iodine-131, has a half life of 8.1 days. explain what this means. draw a particle diagram for a sample 12 particles of I-131 initially after 8.1 days and after16.2 days.

67. ## physics

Radon 86222Rn is a radioactive gas with a half-life 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.

68. ## Chemistry

Can someone link me videos and sites that can teach me the formula to solve these? Or try to help me understand how to solve these? 1.You have 200g of a radioisotope . If the half-life of this radioisotope is 20 days, how many grams will remain after 40

69. ## Chemistry

A 1.50- gas sample at 722 and 25.0 contains 7.56 radon-220 by volume. Radon-220 is an alpha-emitter with a half-life of 55.6s

70. ## chemistry

The disintegration of a radioisotope, such as I-131 to Xe-131, is another example of a first-order reaction. It has a half-life of 8.0 days. I-131 -> Xe-131 + e If you start with 1.40 g I-131, how many grams of I-131 will be left after the following days?

71. ## Chemistry

A 1.50- gas sample at 722 and 25.0 contains 7.56 radon-220 by volume. Radon-220 is an alpha-emitter with a half-life of 55.6. How many alpha particles are emitted by the gas sample in 3.00 minutes?

72. ## modern physics

A radioisotope P has a half-life 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

73. ## Science

The half-life of randon-222 is 8 days. What was the original mass if 6 grams remains after 24 days?

74. ## chem

A sample of radon has an activity of 80,000 Bq. If the half-life of radon is 15 h, how long before the sample's activity is 5,000 Bq?

75. ## chemisty

Chromium-51 is a radioisotope that is used to assess the lifetime of red blood cells The half-life of chromium-51 is 27.7 days. If you begin with 30.1 mg of this isotope, what mass remains after 44.6 days have passed?

76. ## physics

If the physical half-life of sulfur-35 is 87.1 days, and the biologic half-life in the testicle is 632 days, what is its effective half-life in this organ? I know i have to find the time and then the half-life. But im having trouble finding the time

77. ## 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 half-life of the isotope.

78. ## Chemistry

Determine the total time that must elapse until only ¼ of an original sample of the radioisotope Rn-222 remains unchanged.

79. ## chemistry

The disintegration of a radioisotope, such as I-131 to Xe-131, is another example of a first-order reaction. It has a half-life of 8.0 days. I-131 -> Xe-131 + e If you start with 1.40 g I-131, how many grams of I-131 will be left after the following days?

80. ## Chemistry

Technetium-99m is an ideal radioisotope for scanning organs because it has a half-life of 6.0 hr and is a pure gamma emitter. Suppose that 200mg were prepared in the technetium generator this morning. How many milligrams would remain after the following

81. ## Chemistry

Technetium-99m is an ideal radioisotope for scanning organs because it has a half-life of 6.0 hr and is a pure gamma emitter. Suppose that 200mg were prepared in the technetium generator this morning. How many milligrams would remain after the following

82. ## engineering

A certain amount of radioisotope (986.8 x 10-9 kg) is used to make the dial of a watch glow in the dark. If the half-life of this isotope is 3.69 x 103 years, how many kilograms of the radioisotope will disappear while the watch is in use for fifty years?

83. ## physics

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

84. ## Math

1. Iodine-131 is used to find leaks in water pipes it has a half life of 8.14 days. If 36 days have passed and there is now 2.34g left. What is the initial amount? 2. Sr-85 is used in bone scans and has a half life of 64.9 days. If there is 23 percent of

85. ## 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

86. ## Physic

A radioactive element x has half life of 30 days and will decay to become another new element Y.. a) calculate decay constant b) how long it will take for 90% of the no.Of atom in radioisotope x to decay?

87. ## Physic

A radioactive element x has half life of 30 days and will decay to become another new element Y.. a) calculate decay constant b) how long it will take for 90% of the no.Of atom in radioisotope x to decay?

88. ## Physic

A radioactive element x has half life of 30 days and will decay to become another new element Y.. a) calculate decay constant b) how long it will take for 90% of the no.Of atom in radioisotope x to decay?

89. ## 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?

90. ## earth science

if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days

91. ## earth science

if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days

92. ## Chemistry

a sample of radioisotope has a count rate measured by a Muller-Geiger counter of 160 counts per minute. this drop to 20 counts per minute in 1 hour. What is the half life of this source.

93. ## math

Iodine-131 is a radioactive isotope used in the treatment of thyroid conditions. It has a half-life of 8 days. Half-life is the amount of time it takes for half of the substance to decay (or disappear). If a patient is given 20 mg of iodine-131, how much

94. ## 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)

95. ## science

Suppose a laboratory has a 31 g sample of polonium-210. The half-life of polonium-210 is about 138 days. How many half-lives of polonium-210 occur in 966 days? How much polonium is in the sample 966 days later?

96. ## 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?

97. ## Engineering Math

An unknown radioactive element decays into non-radioactive 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

98. ## 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?

99. ## Math

You have just isolated a new radioactive element. If you can determine its half-life, 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

100. ## Physics

An industrial worker accidentally inhaled a radioisotope with an activity of 0.200 kBq. The substance swallowed has a very long effective half-life and therefore the activity will not change significantly during the workerâ€™s lifetime. Every decay of