A solution of selenium-75, a radioisotope used in the diagnosis of pancreatic disease, is found just prior to administration to have an activity of 44 μCi/mL. If 3.98 mL were delivered intravenously to the patient, what dose of Se-75 (in μCi) did the patient receive?
Ch.11 Nuclear Chemistry
Chapter 11, Problem 29
What is wrong with the following decay curve? Explain. 
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Identify the type of decay process represented by the curve. Typically, decay curves are exponential, representing processes like radioactive decay or first-order chemical reactions.
Observe the shape of the curve. In a typical exponential decay, the curve should approach zero asymptotically, meaning it never actually reaches zero but gets infinitely close.
Check the y-axis values. The graph shows the sample remaining in grams per 100 grams of the sample. In a proper decay curve, the values should decrease continuously and never become negative.
Analyze the x-axis values. The time should be consistent with the half-life or decay constant of the substance, showing a consistent rate of decay over time.
Evaluate the end behavior of the curve. The curve should not flatten out completely if it represents a true decay process, as this would imply the sample stops decaying, which is not typical for exponential decay.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Radioactive Decay
Radioactive decay is the process by which an unstable atomic nucleus loses energy by emitting radiation. This decay occurs at a predictable rate, characterized by the half-life, which is the time required for half of the radioactive sample to decay. Understanding this concept is crucial for analyzing decay curves, as they typically exhibit an exponential decrease in the quantity of the sample over time.
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Decay Curve
A decay curve graphically represents the amount of a radioactive substance remaining over time. It typically shows a steep decline initially, which gradually levels off as the sample approaches stability. Analyzing the shape and behavior of the curve helps identify inconsistencies or errors in the data, such as deviations from expected exponential decay patterns.
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Exponential Decay
Exponential decay describes a process where the quantity decreases at a rate proportional to its current value. In the context of radioactive decay, this means that the sample's remaining amount decreases rapidly at first and then slows down over time. A proper decay curve should reflect this behavior; any linear or non-exponential trends may indicate errors in measurement or interpretation.
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Related Practice
Textbook Question
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Textbook Question
A typical chest X ray exposes a patient to an effective dose of 0.02 mSv. How many rem is this, and how many chest X rays would a patient have to receive before biological effects would be observed? (The limit from Table 11.6 is >25 rem.)
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Textbook Question
Identify and write the symbol for each of the five nuclides in the decay series shown in Problem 11.25.
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Textbook Question
List three of the five ways in which a nuclear reaction differs from a chemical reaction.
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Textbook Question
How does ionizing radiation lead to cell damage?
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Textbook Question
How can a nucleus emit an electron during β decay when there are no electrons present in the nucleus to begin with?
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