Tritium has a half-life of 12.26 years. A 5.0 ml sample of triturated water has an activity of 2.4 * — Nuclear Chemistry and Radioactivity Chemistry Question

💡 Solution & Explanation

The initial activity is A_0 = 2.4 * 10^9 cpm and the final activity is A = 3.0 * 10^8 cpm. The fraction of remaining activity is A / A_0 = (3.0 * 10^8) / (2.4 * 10^9) = 1/8. Since A / A_0 = (1/2)^n, we have (1/2)^n = 1/8 = (1/2)^3, which means exactly n = 3 half-lives have elapsed. The time taken is t = n * t_1/2 = 3 * 12.26 years = 36.78 years.