Radioactive Decay and Half-Life Concepts

The video tutorial explains the radioactive decay of strontium-90, a beta-decaying isotope with a half-life of 28.8 years. It covers how to graph the decay process, calculate the remaining isotope after multiple half-lives, and apply first order kinetics and integrated rate laws to determine the rate constant and remaining mass of the isotope over time.

What is the half-life of Strontium-90?

• 115.2 years

• 14.4 years

• 28.8 years

• 57.6 years

If you start with 10 grams of Strontium-90, how much will remain after one half-life?

• 7.5 grams

• 5 grams

• 2.5 grams

• 10 grams

After 115.2 years, how many half-lives have passed for Strontium-90?

• Two

• Five

• Three

• Four

Which of the following is a correct approach to calculate the remaining isotope after multiple half-lives?

• Multiply the initial amount by 2

• Divide the initial amount by the number of half-lives

• Multiply the initial amount by (1/2) raised to the number of half-lives

• Add the initial amount to the number of half-lives

In a first order reaction, the rate of reaction is proportional to which of the following?

• Concentration to the first power

• Concentration to the second power

• Inverse of the concentration

• Square of the concentration

What is the formula for the rate constant (k) in terms of half-life for a first order process?

• k = 0.693 / half-life

• k = half-life * 0.693

• k = half-life / 0.693

• k = 0.693 * half-life

What is the integrated rate law for a first order reaction?

• ln[A] = kt + ln[A]₀

• [A] = -kt + [A]₀

• ln[A] = -kt + ln[A]₀

• [A] = kt + [A]₀

If the rate constant (k) for Strontium-90 is 0.0241 per year, what is the remaining amount after 2 years starting with 1 gram?

• 0.953 grams

• 0.900 grams

• 0.850 grams

• 0.800 grams

What mathematical operation is used to remove the natural log in the integrated rate law?

• Division

• Square root

• Exponentiation

• Multiplication

How does the mass of a radioactive sample relate to the number of radioactive nuclei?

• Mass is unrelated

• Mass is inversely proportional

• Mass is directly proportional

• Mass is exponentially related