# Given the formula A=A0e^(kt) Where A0 is the original mass, and A is material present at t The half life of Pu239 is 24100 years, calculate how long it takes for Pu239 to decay to 70% of its original mass

51,524 results
1. ## Math

Given the formula A=A0e^(kt) Where A0 is the original mass, and A is material present at t The half life of Pu239 is 24100 years, calculate how long it takes for Pu239 to decay to 70% of its original mass.
2. ## pre calculus

The age of a document is in dispute, so archaeologists test for carbon-14. Due to radioactive decay, the amount A of carbon -14 present compared to the initial amount A0 after t years is given by the formula A(t) = A0e^-0.000124t . If 72% of the original
3. ## Algebra 1

The function A = A0e-0.01386x models the amount in pounds of a particular radioactive material stored in a concrete vault, where x is the number of years since the material was put into the vault. If 500 pounds of the material are initially put into the
4. ## precalculus

The function A=A0e^(-0.0099x) models the amount in pounds of a particular radioactive material stored in a concrete vault, where x is the number of years since the material was put into the vault. If 600 pounds of the material are initially put into the
5. ## Physics check

A certain radioactive isotope has a half-life of one hour. At noon, 100g of the material is present. How much of the original isotope will be present at 3:00 p.m.----1/8 6:00 p.m.-----1/16 10:00 p.m.-----1/32 Are these correct?
6. ## Math

Exponential decay problem After how many years will \$100 invested at an annual rate of 6% compounded continuously be worth at least 450\$? (Use the formula An=A0e^rt)
7. ## Math

if salary increased by 10% last year and then 8% this year. and original salary was \$50,000 per year. what is present salary since he has received the two raises? find the relative change between his original salary and his present salary. overall his
8. ## Physics

dear Sir, I have some questions based on proportional reasoning and I hope you can help me thanks Larry king 1.5 Suppose that in a certain atmospheric situation, a falling raindrop, having an initial mass of 0.010g. collects smaller droplets by collision
9. ## physics concepts (please check over my work)

A uniform cyclinder made of lead has the same mass and the same length as a uniform solid cylinder made of wood. The rotatonal inertia of the lead cylinder compared to the wooden one is: I thought at first that the rotational inertia cannot be known or
10. ## Math - Excel

Hi, I need to write an Excel formula and I am trying to double check my work. We are asked to find the difference and relative difference for this account. So the values are: \$10,000 \$10,700 \$11,400 \$12,100 \$12,800 \$13,500 etc. The difference for each is
11. ## Chemistry

The biomass formula for a yeast is CH1.66 00.269 N0.194. The formula accounts for 92% of dry mass; the other 8% is inorganic material (ash). When grown on C6H14, the yield on biomass is 1.4 gcell/gsubstrate. What is the respiratory quotient (mole CO2
12. ## social diversity

I have to present to my social diversity class tomorrow. The section in the textbook the teacher gave me is on The Justified Elite. She doesn't want me to read straight from the book, but to present the material in a creative way, such as a poem, etc. I
13. ## chemistry

A sample of silver chromate (Ag2CrO4) has a mass of 29.0 g. (a) How many Ag+ ions are present? (b)What is the mass in grams of one formula unit of silver chromate? (c) How many CrO42- ions are present?
14. ## Chemistry

A pure white solid material that looks like table salt releases gas when heated under certain conditions. There is no change in the appearance of the solid, but the reactivity of the material changes. Did a chemical or physical change occur? How do you
15. ## Physics

Since moment of inertia is a scalar quantity, a compound object made up of several objects joined together has a moment of inertia which is the scalar sum of the individual moments of inertia. A) A wooden cylinder has mass m and radius R. To be used as a
16. ## chemistry

I did a lab the other day where we separated a mixture of NaCl, SiO2, and CaCO3. The Mixture was made by my professor and we did not know the original amounts of each compound. After recovering all of the compounds we found that there was.. 36.4% NaCl
17. ## chemistry

I did a lab the other day where we separated a mixture of NaCl, SiO2, and CaCO3. The Mixture was made by my professor and we did not know the original amounts of each compound. After recovering all of the compounds we found that there was.. 36.4% NaCl
18. ## chemistry

I did a lab the other day where we separated a mixture of NaCl, SiO2, and CaCO3. The Mixture was made by my professor and we did not know the original amounts of each compound. After recovering all of the compounds we found that there was.. 36.4% NaCl
19. ## chemistry

I did a lab the other day where we separated a mixture of NaCl, SiO2, and CaCO3. The Mixture was made by my professor and we did not know the original amounts of each compound. After recovering all of the compounds we found that there was.. 36.4% NaCl
20. ## Chemistry

I did a lab the other day where we separated a mixture of NaCl, SiO2, and CaCO3. The Mixture was made by my professor and we did not know the original amounts of each compound. After recovering all of the compounds we found that there was.. 36.4% NaCl
21. ## chemistry

I did a lab the other day where we separated a mixture of NaCl, SiO2, and CaCO3. The Mixture was made by my professor and we did not know the original amounts of each compound. After recovering all of the compounds we found that there was.. 36.4% NaCl
22. ## physics

If the mass of a material is 102 grams and the volume of the material is 21 cm3, what would the density of the material be?
23. ## earth science

If the mass of a material is 76 grams and the volume of the material is 23 cm3, what would the density of the material be?
24. ## science

u have 2 cars moving at the same mass and speed collide and stick together what is the momentum? a. twice the original b. half the original c. the same as the original d. 10 times the original
25. ## ENGLISH

You'll be alert, engrosed in the (14)material.And concentrated 100 percent. a) no change b) material, and c) material; and d) material and After reading it over and over, I think b) a comma after material would be the correct answer. I think this is a
26. ## physics

pls what is the formula for calculating period given gravity, mass and length of the material
27. ## narbonne high

What is the percent mass of KClO3 in a mixture if the original starting material weighted 3.58(g) and the mass of KClO3 in mixture is 1.67(g)
28. ## Math

Can you please help with this geometry question. An open box is formed from a square piece of material by cutting 2-in squares from each corner of the material and folding up the sides. If the volume of the box that is formed is to be 72 in cubed, what was
29. ## Math

A radioactive substance decays according to the formula Q(t) = Q0e−kt where Q(t) denotes the amount of the substance present at time t (measured in years), Q0 denotes the amount of the substance present initially, and k (a positive constant) is the
30. ## Math

A radioactive substance decays according to the formula Q(t) = Q0e−kt where Q(t) denotes the amount of the substance present at time t (measured in years), Q0 denotes the amount of the substance present initially, and k (a positive constant) is the
31. ## math

according to the smithsonian institute, many of the original stones were removed and or eroded. The length of one side of the square base originally measured 207 ft. less than twice the height. The original volume of the great pyramid was 91,394,008
32. ## Chemistry;HELP

Use the 5-step method and be sure to include units where appropriate. Round your answers to the correct number of significant digits. Mass m Density = -------------- or D = ------ Volume v Adjust the density formula and solve the problems below: m D =
33. ## Finance

Present value, How do I calculate the present value of: 7,000.00 in 5 years at a quarterly discount rate of 6%? I have read over the material, but I don't get it. Thank you
34. ## chemistry

Suppose a reaction has the equilibrium constant K = 2.3 10-7 at a particular temperature. Will there be a large or small amount of unreacted starting material present when this reaction reaches equilibrium? a)There will be a small amount of unreacted
35. ## Chemistry

If you divide the molar mass of a compound by the empirical formula mass, what is the result? That division should be VERY close to a whole number. Usually, 0.9 to 1.1 or 1.9 to 2.1 (all depending upon the accuracy and precision of experimental data). That
36. ## Chem

If compound X has a first-order half-life of 24 seconds, how long would you have to wait for only 33% of the original material to be left? Explain why not knowing original Molarity of X does not effect this problem.
37. ## science

As redioactive material decays and the percentage of new material in the original sample increases, does the age of the sample substance increase, decrease, or remain the same?
38. ## Chemistry Lab

You are given 350 mL a stock solution of 1.66E-02 M benzoic acid, MW = 122.125 g/mol. Answer the following questions. A. What is the number of moles present in the original stock solution? B. You need to dilute the benzoic acid stock solution to 1.24E-03
39. ## Chemistry Lab

You are given 350 mL a stock solution of 1.66E-02 M benzoic acid, MW = 122.125 g/mol. Answer the following questions. A. What is the number of moles present in the original stock solution? B. You need to dilute the benzoic acid stock solution to 1.24E-03
40. ## 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?
41. ## physical science

If the mass of a material is 99 grams and the volume of the material is 22 cm3, what would the density of the material be? (in g/cm3) i don't know how to find the answer.
42. ## math

A material has a half-life of 12 hours. If initially there are 4 grams of the material, how much is present after 8 hours? I know the answer is 8/3, but how would you solve this using calculus? please help.
43. ## Physics

If the density of atoms in a material is 10^26 metres-3, and 0.04% of a beam of neutrons is stopped in a 2 cm slab of the material What is the cross section ?? No idea can anyone supply a formula ?? thanks
44. ## Materials Science and Engineering

Energy dispersive x-ray spectroscopy (EDX) is a commonly used characterization technique in Materials Science to determine the elemental composition of materials. To do this, EDX measures the emitted characteristic x-rays from materials (e.g. Kα),
45. ## Chemistry;HELP

Use the 5-step method and be sure to include units where appropriate. Round your answers to the correct number of significant digits. Mass m Density = -------------- or D = ------- Volume v Adjust the density formula and solve the problems below: m D =
46. ## Physics

Given the following about a spring: mass = 20.0 kg height initial = 5.25 m (above the ground) height final = 2.17 m (above the ground with the mass attached) delta y initial = 0.00 m There are several questions I must answer from this. 1. What is the value
47. ## Physics

If the density of atoms in a material is 1026 metres-3, and 0.04% of a beam of neutrons is stopped in a 2 cm slab of the material What is the cross section ?? No idea can anyone supply a formula ?? thanks
48. ## Physics

Given the following about a spring: mass = 20.0 kg height initial = 5.25 m (above the ground) height final = 2.17 m (above the ground with the mass attached) delta y initial = 0.00 m There are several questions I must answer from this. 1. What is the value
49. ## Chem-Lab-HELP!!

Heating 1.124g of an unknown NaHCO3-NaCl mixture resulted ina mass loss of 0.270g. 1) Calculate the mass of NaHCO3 present in the original mixture. 2) Calculate the mass percent of NaHCO3 in the uknown mixture
50. ## ap chemistry

18. Answer the following question that relate to the analysis of chemical compounds. (a) A compound containing the elements C, H, N, and O is analyzed. When a 1.2359g sample is burned in excess oxygen, 2.241g of CO2(g) is formed. The combustion analysis
51. ## physics

If the mass of a material is 95 grams and the volume of the material is 14 cm3, what would the density of the material be? 6.785 g/cm3?
52. ## chemistry

If a student attempts to identify an unknown compound by methodused in this experiment. She finds that when she heated a sampleweighing 0.4862 g the mass went down appreciably, to 0.3067 g. Whenthe product was converted to chloride, the mass went up, to
53. ## 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
54. ## College Algebra

Show all work When a person has a cavity filled, the dentist typically administers a local anesthetic. After leaving the dentist's office, one's mouth often feels numb for several hours. If a shot of anesthesia is injected into the bloodstream at the time
55. ## Chem

How many chlorine atoms are in 5.0 g of C2H3Cl3O2? What mass of C2H3Cl3O2 would contain 1.0g Cl? There are 6.02 x 10^23 atoms in a mole of anything. Calculate the molar mass of your compound, that mass will contain 6.02 x 10^23 molecules of that material
56. ## science

what material can we use as an indicator of acid?in other words,what material can we use to test a food to see if acid is present? what is the relationship between the concentration of acid in a liquid and the amount of carbon dioxide produced?
57. ## algebra

A radioactive substance decays according to the formula A=A0e^kt where A0 is the initial amount of substance (in grams) A is the amount of substance(in grams) after t years k is a constant The half-life of the substance is 10 years.If we begin with 20g of

1. A granite rock is thought to be about 2 billion years old. why is it not possible to determine the age of the Rock using carbon-14 dating? 2. A hair sample has 80% of its original carbon-14 present. what is the age of the sample? 3. A bone fragment has
59. ## Algebra 2 help...

A half life of a certain radioactive is 36 days. An initial amount of the material has a mass of 487 kg. Write an exponential function that models the decay of this material. Find how much radioactive material remains after 5 days. Round your answer to the
60. ## College Chemistry

how do i calculate the moles of Na2CO3 present in the original 25.00mL aliquot of carbonate solution?? the tared mass of Na2CO3 is 1.5179g
61. ## AP Chemistry

A 23.9475 g sample of impure magnesium carbonate was heated to complete decomposition according to the equation MgCO3(s) → MgO(s) + CO2(g). After the reaction was complete, the solid residue (consisting of MgO and the original impurities) had a mass of
62. ## Pre-Calculus

The population of a particular type of bacteria doubles in number every 12 hours. a)if there are 8 bcteria initially, write an equation that models the number of bacteria present after x 12 hours. b)How many bacteria will be present after 5 days? by using
63. ## AP Chemistry

A 21.0054 g sample of impure magnesium carbonate was heated to complete decomposition according to the equation MgCO3(s) → MgO(s) + CO2(g) . After the reaction was complete, the solid residue (consisting of MgO and the original impurities) had a mass
64. ## AP Chemistry

A 28.4858 g sample of impure magnesium carbonate was heated to complete decomposition according to the equation MgCO3(s)→MgO(s) + CO2(g).After the reaction was complete, the solid residue (consisting of MgO and the original impurities) had a mass of
65. ## AP Chemistry i need help!

A 21.5997 g sample of impure magnesium carbonate was heated to complete decomposition according to the equation MgCO3(s) → MgO(s) + CO2(g). After the reaction was complete, the solid residue (consisting of MgO and the original impurities) had a mass
66. ## chemistry

A 21.8603 g sample of impure magnesium carbonate was heated to complete decomposition according to the equation MgCO3(s) → MgO(s) + CO2(g). After the reaction was complete, the solid residue (consisting of MgO and the original impurities) had a mass
67. ## AP chemistry

A 22.709 g sample of impure magnesium carbonate was heated to complete decomposition according to the equation MgCO3(s) → MgO(s) + CO2(g). After the reaction was complete, the solid residue (consisting of MgO and the original impurities) had a mass
68. ## Chemistry

A 28.4378 g sample of impure magnesium carbonate was heated to complete decomposition according to the equation MgCO3(s) → MgO(s) + CO2(g). After the reaction was complete, the solid residue (consisting of MgO and the original impurities) had a mass
69. ## Chemistry

A compound of B and H is found to have a mass percent composition of 81.1% Boron. Its empirical formula is B2H5. A mass spectrometry experiment tells us that the molecular mass is 53.3 g/mol. What is its molecular formula? So I feel like this is a trick
70. ## Criminal Law

What should an investigator do if contraband that does not come under the present warrant is found in pursuit of items covered under the original warrant? A. Focus on the original warrant B. Seize the contraband under the present warrant C. Get a secondary
71. ## Chemistry

Hi Im reposting incase my original post doesn't get read. Please see bottom for additional info that I need help getting verified. Many thanks Hi Please help verify my answer to the following question: 0.500g of pure phosphorous was burned in excess pure
72. ## math

can anyone help please, i need a simple formula for working out taxes.if i had any number i need to know what the base was before 16% tax was added. i know the formula if the tax was 17.5%,what ever the total is if you divide that by 47 then x that by 7
73. ## chemistry

chemistry posted by Naomi today at 8:03pm. The material Magnesium Sulfate What mass of dry material would be needed to make an aqueous solution with a molality of 4 moles/kg solution ? What mass of water is needed? 4 (24.305+ 32.065+ (4 x 15.999)) =481.5
74. ## physics

A block of mass 7.33 kg in outerspace is moving at 1.72 m/s with no external forces acting on it. After an explosion, the block is split into two parts both having mass equal to half the mass of the original block. The explosion supplies the two masses
75. ## math

An open box is to be made from a square piece of material by cutting four-centimeter squares from each corner and turning up the sides (see figure). The volume of the finished box is to be 576 cubic centimeters. Find the size of the original piece of
76. ## Math

An open box is to be made from a square piece of material by cutting four-centimeter squares from each corner and turning up the sides (see figure). The volume of the finished box is to be 144 cubic centimeters. Find the size of the original piece of
77. ## chemistry

The material Magnesium Sulfate What mass of dry material would be needed to make an aqueous solution with a molality of 4 moles/kg solution ? What mass of water is needed? 4 (24.305+ 32.065+ (4 x 15.999)) =481.5 ?Not sure where to go from here or if the
78. ## Physics

The density of air near the earth's surface is 1.29 kg?m^3. If a helium balloon with a mass of 1 kg floats in air without rising or falling,what is the minimum volume of helium in the balloon? (presume that the mass of the material making up the balloon is
79. ## math

When the price of an article is reduced by 5/8 of its former value, the number of article sold is increased to 32/27 of the original amount. The present daily revenues is what fraction of the original?
80. ## Chemistry

Hi Please help verify my answer to the following question: 0.500g of pure phosphorous was burned in excess pure oxygen to give a product that has a mass of 1.145 g. What is the empirical formula of the resulting compound? By the use of a mass spectrometer
81. ## Finding the Molecular Formula

A certain compound containing only carbon and hydrogen was found to have a vapor density of 2.550 g/L at 100 degrees C and 760 mm Hg. If the empirical formula of this compound is CH, what is the molecular formula of this compound? I had some ideas as to
82. ## college physics

Please help! the below questions are driving me crazy. Thanks Larry King 1) Suppose that in a certain atmospheric situation, a falling raindrop, having an initial mass of 0.010g. collects smaller droplets by collision at such a rate that, after 10s, it has
83. ## math

find the present value using the present value formula. Achieve \$ 225,500 at 8.65% compounded continusly for 8 years 155 days
84. ## math

find the present value using the present value formula. Achieve \$ 225,500 at 8,95% compounded continuously for 8 years, 135 days.
85. ## math

6. The half-life of a certain radioactive material is 32 days. An initial amount of the material has a mass of 361 kg. Write an exponential function that models the decay of this material. Find how much radioactive material remains after 5 days. Round your
86. ## Chemistry

A 28.4288 g sample of impure magnesium car- bonate was heated to complete decomposition according to the equation MgCO3(s) ! MgO(s) + CO2(g) . After the reaction was complete, the solid residue (consisting of MgO and the original impurities) had a mass of
87. ## Chemistry

Mass of unknown solution=25.671 Mass ethanol =8.243 Assuming that prior experiments have shown the single-step extraction removes only 72.0 % of the ethanol, the mass of ethanol in your original unknown is 11.45 Mass percent ethanol =44.6 % Given a density
88. ## Math (Word Problem)

An open gift box is to be made from a square piece of material by cutting four-centimeter squares from the corners and turning up the sides. The volume of the finished box is to be 576 cubic centimeters. How to find the size of the original piece of
89. ## Chemistry

I am completing my lab and cannot figure this out. I need someone to go over it and make sure I am right because I can't figure out why my empirical formula does not match the molecular formula. #7 is the one I am really having a problem with, but here is

A material has an optical purity of 50%. How much of each of the enantiomers is present. The R enantiomer of a material has rotation of +35. what is the rotation of the S enantiomers.
91. ## Math

A toy company has increased their size of one of their dolls. The packaging department has calculated that they need to add 3 inches to each of the dimension of the original packaging (Original height=10 in width=2.75 length=5). What is the new amount of
92. ## Math

Find how much must be deposited now (present value) at % simple interest so that in 6 years an account will contain \$8958 (future value). present value = \$ WHAT FORMULA DO I NEED TO USE TO HELP ME SOLVE THE PROBLEM?
93. ## physics

Two capacitors, identical except for the dielectric material between their plates, are connected in parallel. One has a material with a material with a dielectric constant of 2, while the other has a material with a dielectric constant of 3. What is the
94. ## college Physics

Dear Sir, Please help. I am struggling with the below problems for a very long time. thanks Larry King 1) Suppose that in a certain atmospheric situation, a falling raindrop, having an initial mass of 0.010g. collects smaller droplets by collision at such
95. ## chem

how to set up or approach these 1. Calculate the mass in grams of iodine (I2) that will react completely with 48.9 g of aluminum (Al) to form aluminum iodide (AlI3). Do I need to find the mass as a whole for the entire compound, then convert? 2. The
96. ## math

8. The half-life of a certain radioactive material is 71 hours. An initial amount of the material has a mass of 722 kg. Write an exponential function that models the decay of this material. Find how much radioactive material remains after 17 hours. Round
97. ## Chemistry

2.500g sample of a mixture of sodium carbonate and sodium chloride is dissolved in 25.00ml of 0.798M HCl. Some acid remains after the treatment of the sample. If 28.7 ml of 0.0108M NaOH were required to titrate the excess hydrochloric acid how many moles
98. ## chemistry

1. mass of flask + cap = 92.53 g 2. mass of flask + cap + condensate = 94.34 g 3. mass of condensate = 1.81 g 4. volume of flask = 160 ml 5. temperature of water = 99.3 celsius 6. barametric pressure = 757 ml of mercury 7.. molar mass of gas(experimental)
99. ## Physics

A bullet with a mass of 10 imbeds itself in a wooden block of mass 3990g and is free to move. If the speed of the block and bullet together is 50 cm/s just after the impact what was the original speed of the bullet ? what was the right formula to use.? pls
100. ## chemistry

How do you find the mass of a solution if you have 1L of 2.5 M MgCl2. I have determined how many moles are present in MgCl2 which was 2.5 and how grams are present which came out to be 238.025g Now I'm asked "What is the mass of the solution and the mass