Kinetics of radioactive decay | Kinetics | AP Chemistry | Khan Academy

TL;DR

Radioactive isotopes decay at a constant rate, determined by their half-life, and can be calculated using exponential decay graphs and mathematical equations.

Transcript

• [Instructor] Strontium-90 is a radioactive isotope that undergoes beta decay. Because radioactive decay is a first-order process, radioactive isotopes have constant half-lives. Half-life is symbolized by t1/2, and it's the time required for 1/2 of a sample of a particular radioactive isotope to decay. For example, the half-life of Strontium-90 is... Read More

Key Insights

• ☢️ Radioactive decay is a first-order process, meaning the rate of decay is proportional to the amount of radioactive material present.
• 🛟 The half-life of a radioactive isotope remains constant regardless of the initial amount of the isotope.
• 💆 Exponential decay graphs can be used to visualize the decrease in mass over time.
• ☠️ The rate constant is determined by the half-life and can be used to calculate the rate of decay at different times.
• ☢️ The integrated rate law for a first-order reaction can be applied to radioactive decay by substituting the concentration of reactant with the number of radioactive nuclei.

Questions & Answers

Q: What is the half-life of Strontium-90?

The half-life of Strontium-90 is 28.8 years, meaning it takes 28.8 years for half of the initial sample to decay.

Q: How can the remaining mass of Strontium-90 be determined after a certain time period?

The remaining mass can be found by dividing the time period by the half-life. Each half-life reduces the mass by half, so the number of half-lives can be used to calculate the final mass.

Q: What is the rate law for radioactive decay?

The rate of radioactive decay is described by the equation rate = k * N^1, where N represents the number of radioactive nuclei in a sample and k is the rate constant.

Q: How can the rate constant for radioactive decay be calculated?

The rate constant can be found using the equation k = 0.693 / t1/2, where t1/2 is the half-life of the radioactive isotope.

Summary & Key Takeaways

• Strontium-90 undergoes radioactive decay through beta decay, with a half-life of 28.8 years.

• The decay of Strontium-90 can be represented on an exponential decay graph, showing the decreasing mass of the isotope over time.

• Calculating the remaining mass of Strontium-90 after a specific time period involves dividing the time by the half-life and using the concept of half-lives.