<< Chapter < Page Chapter >> Page >

(a) Calculate the activity R size 12{R} {} in curies of 1.00 g of 226 Ra size 12{"" lSup { size 8{"226"} } "Ra"} {} . (b) Discuss why your answer is not exactly 1.00 Ci, given that the curie was originally supposed to be exactly the activity of a gram of radium.

(a) 0.988 Ci

(b) The half-life of 226 Ra size 12{"" lSup { size 8{"226"} } "Ra"} {} is now better known.

Show that the activity of the 14 C size 12{"" lSup { size 8{"14"} } C} {} in 1.00 g of 12 C size 12{"" lSup { size 8{"12"} } C} {} found in living tissue is 0.250 Bq.

Mantles for gas lanterns contain thorium, because it forms an oxide that can survive being heated to incandescence for long periods of time. Natural thorium is almost 100% 232 Th size 12{"" lSup { size 8{"232"} } "Th"} {} , with a half-life of 1 . 405 × 10 10 y size 12{1 "." "405" times "10" rSup { size 8{"10"} } } {} . If an average lantern mantle contains 300 mg of thorium, what is its activity?

1.22 × 10 3 Bq

Cow’s milk produced near nuclear reactors can be tested for as little as 1.00 pCi of 131 I size 12{"" lSup { size 8{"131"} } I} {} per liter, to check for possible reactor leakage. What mass of 131 I size 12{"" lSup { size 8{"131"} } I} {} has this activity?

(a) Natural potassium contains 40 K , which has a half-life of 1 . 277 × 10 9 size 12{1 "." "277" times "10" rSup { size 8{9} } } {} y. What mass of 40 K size 12{"" lSup { size 8{"40"} } K} {} in a person would have a decay rate of 4140 Bq? (b) What is the fraction of 40 K size 12{"" lSup { size 8{"40"} } K} {} in natural potassium, given that the person has 140 g in his body? (These numbers are typical for a 70-kg adult.)

(a) 16.0 mg

(b) 0.0114%

There is more than one isotope of natural uranium. If a researcher isolates 1.00 mg of the relatively scarce 235 U size 12{"" lSup { size 8{"235"} } U} {} and finds this mass to have an activity of 80.0 Bq, what is its half-life in years?

50 V has one of the longest known radioactive half-lives. In a difficult experiment, a researcher found that the activity of 1.00 kg of 50 V is 1.75 Bq. What is the half-life in years?

1.48 × 10 17 y size 12{ {underline {1 "." "48" times "10" rSup { size 8{"17"} } y}} } {}

You can sometimes find deep red crystal vases in antique stores, called uranium glass because their color was produced by doping the glass with uranium. Look up the natural isotopes of uranium and their half-lives, and calculate the activity of such a vase assuming it has 2.00 g of uranium in it. Neglect the activity of any daughter nuclides.

A tree falls in a forest. How many years must pass before the 14 C size 12{"" lSup { size 8{"14"} } C} {} activity in 1.00 g of the tree’s carbon drops to 1.00 decay per hour?

5.6 × 10 4 y size 12{ {underline {5 "." 6 times "10" rSup { size 8{4} } y}} } {}

What fraction of the 40 K size 12{"" lSup { size 8{"40"} } K} {} that was on Earth when it formed 4 . 5 × 10 9 years ago is left today?

A 5000-Ci 60 Co source used for cancer therapy is considered too weak to be useful when its activity falls to 3500 Ci. How long after its manufacture does this happen?

2.71 y

Natural uranium is 0.7200% 235 U and 99.27% 238 U . What were the percentages of 235 U and 238 U in natural uranium when Earth formed 4 . 5 × 10 9 years ago?

The β size 12{β rSup { size 8{ - {}} } } {} particles emitted in the decay of 3 H (tritium) interact with matter to create light in a glow-in-the-dark exit sign. At the time of manufacture, such a sign contains 15.0 Ci of 3 H size 12{"" lSup { size 8{3} } H} {} . (a) What is the mass of the tritium? (b) What is its activity 5.00 y after manufacture?

(a) 1.56 mg

(b) 11.3 Ci

World War II aircraft had instruments with glowing radium-painted dials. The activity of one such instrument was 1.0 × 10 5 Bq when new. (a) What mass of 226 Ra was present? (b) After some years, the phosphors on the dials deteriorated chemically, but the radium did not escape. What is the activity of this instrument 57.0 years after it was made?

(a) The 210 Po source used in a physics laboratory is labeled as having an activity of 1.0 μ Ci size 12{1 "." 0 m"Ci"} {} on the date it was prepared. A student measures the radioactivity of this source with a Geiger counter and observes 1500 counts per minute. She notices that the source was prepared 120 days before her lab. What fraction of the decays is she observing with her apparatus? (b) Identify some of the reasons that only a fraction of the α size 12{α} {} s emitted are observed by the detector.

(a) 1.23 × 10 3 size 12{ {underline {1 "." "23" times "10" rSup { size 8{ - 3} } }} } {}

(b) Only part of the emitted radiation goes in the direction of the detector. Only a fraction of that causes a response in the detector. Some of the emitted radiation (mostly α size 12{α} {} particles) is observed within the source. Some is absorbed within the source, some is absorbed by the detector, and some does not penetrate the detector.

Armor-piercing shells with depleted uranium cores are fired by aircraft at tanks. (The high density of the uranium makes them effective.) The uranium is called depleted because it has had its 235 U removed for reactor use and is nearly pure 238 U . Depleted uranium has been erroneously called non-radioactive. To demonstrate that this is wrong: (a) Calculate the activity of 60.0 g of pure 238 U size 12{"" lSup { size 8{"238"} } U} {} . (b) Calculate the activity of 60.0 g of natural uranium, neglecting the 234 U and all daughter nuclides.

The ceramic glaze on a red-orange Fiestaware plate is U 2 O 3 and contains 50.0 grams of 238 U , but very little 235 U . (a) What is the activity of the plate? (b) Calculate the total energy that will be released by the 238 U decay. (c) If energy is worth 12.0 cents per kW h , what is the monetary value of the energy emitted? (These plates went out of production some 30 years ago, but are still available as collectibles.)

(a) 1.68 × 10 5 Ci

(b) 8.65 × 10 10 J

(c) $ 2.9 × 10 3

Large amounts of depleted uranium ( 238 U ) are available as a by-product of uranium processing for reactor fuel and weapons. Uranium is very dense and makes good counter weights for aircraft. Suppose you have a 4000-kg block of 238 U . (a) Find its activity. (b) How many calories per day are generated by thermalization of the decay energy? (c) Do you think you could detect this as heat? Explain.

The Galileo space probe was launched on its long journey past several planets in 1989, with an ultimate goal of Jupiter. Its power source is 11.0 kg of 238 Pu , a by-product of nuclear weapons plutonium production. Electrical energy is generated thermoelectrically from the heat produced when the 5.59-MeV α particles emitted in each decay crash to a halt inside the plutonium and its shielding. The half-life of 238 Pu is 87.7 years. (a) What was the original activity of the 238 Pu in becquerel? (b) What power was emitted in kilowatts? (c) What power was emitted 12.0 y after launch? You may neglect any extra energy from daughter nuclides and any losses from escaping γ rays.

(a) 6.97 × 10 15 Bq

(b) 6.24 kW

(c) 5.67 kW

Questions & Answers

what is mutation
Janga Reply
what is a cell
Sifune Reply
how is urine form
Sifune
what is antagonism?
mahase Reply
classification of plants, gymnosperm features.
Linsy Reply
what is the features of gymnosperm
Linsy
how many types of solid did we have
Samuel Reply
what is an ionic bond
Samuel
What is Atoms
Daprince Reply
what is fallopian tube
Merolyn
what is bladder
Merolyn
what's bulbourethral gland
Eduek Reply
urine is formed in the nephron of the renal medulla in the kidney. It starts from filtration, then selective reabsorption and finally secretion
onuoha Reply
State the evolution relation and relevance between endoplasmic reticulum and cytoskeleton as it relates to cell.
Jeremiah
what is heart
Konadu Reply
how is urine formed in human
Konadu
how is urine formed in human
Rahma
what is the diference between a cavity and a canal
Pelagie Reply
what is the causative agent of malaria
Diamond
malaria is caused by an insect called mosquito.
Naomi
Malaria is cause by female anopheles mosquito
Isaac
Malaria is caused by plasmodium Female anopheles mosquitoe is d carrier
Olalekan
a canal is more needed in a root but a cavity is a bad effect
Commander
what are pathogens
Don Reply
In biology, a pathogen (Greek: πάθος pathos "suffering", "passion" and -γενής -genēs "producer of") in the oldest and broadest sense, is anything that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term pathogen came into use in the 1880s.[1][2
Zainab
A virus
Commander
Definition of respiration
Muhsin Reply
respiration is the process in which we breath in oxygen and breath out carbon dioxide
Achor
how are lungs work
Commander
where does digestion begins
Achiri Reply
in the mouth
EZEKIEL
what are the functions of follicle stimulating harmones?
Rashima Reply
stimulates the follicle to release the mature ovum into the oviduct
Davonte
what are the functions of Endocrine and pituitary gland
Chinaza
endocrine secrete hormone and regulate body process
Achor
while pituitary gland is an example of endocrine system and it's found in the Brain
Achor
what's biology?
Egbodo Reply
Biology is the study of living organisms, divided into many specialized field that cover their morphology, physiology,anatomy, behaviour,origin and distribution.
Lisah
biology is the study of life.
Alfreda
Biology is the study of how living organisms live and survive in a specific environment
Sifune
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
Practice Key Terms 8

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Concepts of physics with linear momentum. OpenStax CNX. Aug 11, 2016 Download for free at http://legacy.cnx.org/content/col11960/1.9
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Concepts of physics with linear momentum' conversation and receive update notifications?

Ask