Question

The rate constant for a certain radioactive nuclide is \(1.0 \times 10^{-3} \mathrm{h}^{-1} .\) What is the half-life of this nuclide?

Short answer

The half-life (T) of the radioactive nuclide can be found using the formula \(T = \frac{\ln(2)}{k}\), where k is the rate constant. Given the rate constant \(k = 1.0 \times 10^{-3} h^{-1}\), the half-life of the nuclide is approximately \(T = \frac{\ln(2)}{1.0 \times 10^{-3} h^{-1}} \approx 693\) hours.

Step-by-step solution

1. Write down the given information and formula.

We are given the rate constant (k) for a certain radioactive nuclide: \(k = 1.0 \times 10^{-3} h^{-1}\). We want to find the half-life (T) of this nuclide. The formula connecting these values is: \(T = \frac{\ln(2)}{k}\)

2. Substitute the rate constant into the formula.

Now we can plug in the value of the rate constant k into the formula: \(T = \frac{\ln(2)}{1.0 \times 10^{-3} h^{-1}}\)

3. Calculate the half-life (T).

Divide the natural logarithm of 2 by the rate constant to find the half-life of the nuclide: \(T = \frac{\ln(2)}{1.0 \times 10^{-3} h^{-1}} \approx \frac{0.693}{1.0 \times 10^{-3} h^{-1}} = 693 \, hours\)

4. State the final answer.

The half-life of this radioactive nuclide is approximately 693 hours.

Key concepts

Half-Life in Radioactive Decay

The concept of half-life is essential in understanding radioactive decay. Half-life, denoted as \( T \), represents the time needed for half of a radioactive substance to decay. It's an indicator of how quickly or slowly a substance breaks down. This concept is inverse to stability; shorter half-lives mean rapid decay and vice versa. In the step-by-step solution, the half-life equation is expressed as:
\[T = \frac{\ln(2)}{k}\]where \( \ln(2) \approx 0.693 \) and \( k \) is the rate constant. Half-life remains constant regardless of the initial quantity of the sample, making it a unique characteristic of each radioactive substance. By understanding and calculating half-life, scientists can divulge pivotal information about the age and stability of materials, from archaeological findings to nuclear waste management.

Understanding the Rate Constant

The rate constant, represented by \( k \), is a fundamental parameter in the study of radioactive decay, highlighting the speed of the decay process. It is directly related to how fast the nuclei in a sample disintegrate over time. The rate constant is vital for calculating the half-life of a substance, using the equation:
\[T = \frac{\ln(2)}{k}\]In the context of radioactive decay, the unit of the rate constant is typically reciprocal time (e.g., \( \mathrm{h}^{-1} \) or \( \mathrm{s}^{-1} \)). A higher rate constant implies a more rapid decay, indicating a more unstable isotope. Understanding the rate constant allows for predictions about how long a substance will remain radioactive, thus aiding in important safety and environmental considerations.

The Role of Natural Logarithm

The natural logarithm, denoted as \( \ln \), plays a crucial role in the mathematical representation of radioactive decay. In the formula for half-life, the natural logarithm of 2 (\( \ln(2) \approx 0.693 \)) is used to provide a more direct calculation. This stems from the natural logarithmic nature of exponential decay processes:
\[T = \frac{\ln(2)}{k}\]Natural logarithms stem from the mathematical constant \( e \approx 2.718 \) and are preferred in these calculations due to their inherent properties that simplify growth and decay processes. The inclusion of \( \ln(2) \) ensures that the half-life is precisely determined, allowing the equation to reflect the time it takes for half of the substance to decay. Understanding the use of natural logarithms in these calculations provides deeper insights into the predictability and analysis of decay processes.