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- Half-life and activity
To obtain the most precise value of BE from the equation
, we should take into account the binding energy of the electrons in the neutral atoms. Will doing this produce a larger or smaller value for BE? Why is this effect usually negligible?
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Problems&Exercises
Data from the appendices and the periodic table may be needed for these problems.
An old campfire is uncovered during an archaeological dig. Its charcoal is found to contain less than 1/1000 the normal amount of
. Estimate the minimum age of the charcoal, noting that
.
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A
source is labeled 4.00 mCi, but its present activity is found to be
Bq. (a) What is the present activity in mCi? (b) How long ago did it actually have a 4.00-mCi activity?
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(a) Calculate the activity
in curies of 1.00 g of
. (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
is now better known.
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Show that the activity of the
in 1.00 g of
found in living tissue is 0.250 Bq.
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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%
, with a half-life of
. If an average lantern mantle contains 300 mg of thorium, what is its activity?
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Cow’s milk produced near nuclear reactors can be tested for as little as 1.00 pCi of
per liter, to check for possible reactor leakage. What mass of
has this activity?
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(a) Natural potassium contains
, which has a half-life of
y. What mass of
in a person would have a decay rate of 4140 Bq? (b) What is the fraction of
in natural potassium, given that the person has 140 g in his body? (These numbers are typical for a 70-kg adult.)
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There is more than one isotope of natural uranium. If a researcher isolates 1.00 mg of the relatively scarce
and finds this mass to have an activity of 80.0 Bq, what is its half-life in years?
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has one of the longest known radioactive half-lives. In a difficult experiment, a researcher found that the activity of 1.00 kg of
is 1.75 Bq. What is the half-life in years?
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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.
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A tree falls in a forest. How many years must pass before the
activity in 1.00 g of the tree’s carbon drops to 1.00 decay per hour?
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A 5000-Ci
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?
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Questions & Answers
Biology is a branch of Natural science which deals/About living Organism.
evolutionary history and relationship of an organism or group of organisms
AI-Robot
cell is the smallest unit of the humanity biologically
Abraham
HOW CAN MAN ORGAN FUNCTION
the diagram of the digestive system
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They formed in two ways first when one sperm and one egg are splited by mitosis or two sperm and two eggs join together
Oluwatobi
Genetics is the study of heredity
Misack
how does twins formed?
Misack
discuss biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles
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discuss the biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles in an essay form
list any five characteristics of the blood cells
Shaker
lack electricity and its more savely than electronic microscope because its naturally by using of light
advantage of electronic microscope is easily and clearly while disadvantage is dangerous because its electronic. advantage of light microscope is savely and naturally by sun while disadvantage is not easily,means its not sharp and not clear
Abdullahi
cell theory state that every organisms composed of one or more cell,cell is the basic unit of life
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is like gone fail us
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cells is the basic structure and functions of all living things
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is organisms that are similar into groups called tara
Yamosa
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Source:
OpenStax, College physics for ap® courses. OpenStax CNX. Nov 04, 2016 Download for free at https://legacy.cnx.org/content/col11844/1.14
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