Rate of Radioactive Decay

For the radioactive decay of lead-202 the decay constant is 1.32 x 10^-5 yr^-1. How long will it take in hours to decrease to 53% of its initial amount?

• A. 5.72 x 10⁴ hrs
• B. 5.01 x 10⁹ hrs
• C. 4.81 x 10⁴ hrs
• D. 4.21 x 10⁸ hrs

During World War I radium-226 was used in the manufacturing of luminous paint. If it takes 2.12 x 10⁴ days for its degradation to be 2.49% complete, what is its decay constant?

• A. 1.74 x 10^–4 days^–1
• B. 1.08 x 10^–5 days^–1
• C. 1.19 x 10^–6 days^–1
• D. 2.14 x 10^–5 days^–1

If the decay constant for polonium-209 is 6.80 x 10^-3 ys^-1, what fraction of it remains after 1.1 x 10⁴ years?

• A. 9.00 x 10^–30
• B. 3.27 x 10^–33
• C. 8.24 x 10^–42
• D. 9.13 x 10^–43