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Gallium-67 \(\left(t_{44}=78.25\) hours) is used in the medical \right. diagnosis of certain kinds of tumors. If you ingest a compound containing 0.015 mg of this isotope, what mass (in milligrams) remains in your body after 13 days? (Assume none is excreted.)

Short Answer

Expert verified
0.00107 mg of Gallium-67 remains after 13 days.

Step by step solution

01

Understand the Half-Life

The half-life of Gallium-67 is given as 78.25 hours. This means that every 78.25 hours, the mass of Gallium-67 reduces to half of its initial value.
02

Convert Time to Hours

The time given is 13 days. Convert this to hours: \(13 \times 24 = 312\) hours.
03

Calculate the Number of Half-Lives

Determine how many half-lives (\( n \)) have occurred in 312 hours using the formula \( n = \frac{312}{78.25} \approx 3.987\).
04

Calculate Remaining Mass

Use the formula for exponential decay: \( m = m_0 \times \left( \frac{1}{2} \right)^n \), where \( m_0 = 0.015 \) mg and \( n = 3.987 \). Thus, \( m = 0.015 \times (0.5)^{3.987} \approx 0.00107 \text{ mg} \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

half-life calculation
A half-life is a distinct concept used to describe the rate of decay for radioactive substances. In simple terms, it's the amount of time it takes for half of a radioactive material to decay and become stable. Every time a half-life period passes, half of the remaining radioactive substance turns into a different form, often resulting in a decrease of the initial mass by 50%. Thus, understanding the half-life helps predict how quickly a substance diminishes over time.

To calculate the remaining amount of a substance after a certain period, start by determining its half-life. If, for example, a substance has a half-life of 78.25 hours, this means every 78.25 hours, exactly half of it will decay. When dealing with exercises involving half-life calculations, it's essential to track how many half-lives have transpired during the given time period. This is done by dividing the total time by the half-life duration, leading us to the exact number of half-lives that the substance underwent.

Once you have the number of half-lives, the calculation of the remaining mass becomes straightforward. You use the exponential decay formula, which will show how much of the original substance is left after each half-life interval.
Gallium-67
Gallium-67 is a radioactive isotope often used in medical settings to diagnose conditions such as certain types of tumors. Its unique properties make it particularly suited for imaging, allowing doctors to pinpoint troubled areas within the body with precision. One of its defining factors is its half-life of approximately 78.25 hours, which indicates how rapidly it decays.

Thanks to its radioactivity, it emits gamma rays that can be detected by special imaging equipment. This feature is utilized in what is known as Gallium-67 scans, which play a crucial role in detecting and analyzing the spread of cancers, as well as inflammatory conditions. Its utility, combined with the understanding of half-life principles, allows for effective diagnostic techniques without requiring the substance to remain in the body for extended periods.

Understanding how Gallium-67 functions and decays over time is vital for safe and efficient use in medical treatments. The decay patterns ensure that by the time a procedure is over, the isotope will have reduced significantly, minimizing any long-term exposure effects.
exponential decay formula
The exponential decay formula is a key mathematical representation used when studying substances that decrease in quantity over time, especially applicable in radioactive decay. It expresses the relationship between the number of remaining entities of a substance and the initial amount.

The formula is typically written as \[m = m_0 \times \left( \frac{1}{2} \right)^n\]where:
  • \( m \) is the remaining mass of the substance after a certain time.
  • \( m_0 \) is the initial mass of the substance.
  • \( n \) represents the number of half-lives that have passed.

To use the formula effectively, begin with calculating \( n \), the number of half-lives, by dividing the total elapsed time by the half-life period. Then, apply it in the equation to find out the remaining mass.

This formula is crucial for accurately predicting the behavior of decaying substances, such as Gallium-67, over specified time intervals. By understanding and applying this central concept, one can make informed predictions about how much a radioactive material will diminish within a given timeframe.

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Most popular questions from this chapter

Copper(II) acetate containing \(^{64} \mathrm{Cu}\) is used to study brain tumors. This isotope has a half-life of 12.7 hours. If you begin with \(25.0 \mu \mathrm{g}\) of \(^{64} \mathrm{Cu}\), what mass remains after 63.5 hours?

Predict the probable mode of decay for each of the following radioactive isotopes, and write an equation to show the products of decay. (a) bromine-80 (c) cobalt-61 (b) californium-240 (d) carbon-11

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Iodine-131 is used to treat thyroid cancer. (a) The isotope decays by \(\beta\) particle emission. Write a balanced equation for this process. (b) Iodine-131 has a half-life of 8.04 days. If you begin with \(2.4 \mu \mathrm{g}\) of radioactive \(1^{31} \mathrm{I}\), what mass remains after 40.2 days?

Radioactive isotopes are often used as "tracers" to follow an atom through a chemical reaction. The following is an example of this process: Acetic acid reacts with methanol, \(\mathrm{CH}_{5} \mathrm{OH}\), by eliminating a molecule of \(\mathrm{H}_{2} \mathrm{O}\) to form methy acetate, \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{CH}_{3}\). Explain how you would use the radioactive isotope \(^{15} \mathbf{O}\) to show whether the oxygen atom in the water product comes from the - OH of the acid or the - OH of the alcohol.

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