Solution: A has a half-life of 3 hrs, so 18 hrs = 6 half-lives.ī has a half-life of 6 hrs, so 18 hrs = 3 half-lives.Īfter 6 half lives, the fraction of A left is 1/(2 6) = 1/64 What is the expected ratio A/B after 18 hours? The half-life of A is 3 hours and, that of B, 6 hours. Initially, the sample composition is 1:1, i.e., the same number of nuclei A as nuclei B. Problem #28: A sample of radioactive isotopes contains two different nuclides, labeled A and B. In 24 hours, the sample goes from 100% to 95% How long will it take for half the original to decay? Problem #27: You have 20.0 grams of P-32 that decays 5% daily.

Therefore the total amount of elapsed time for A was 2.Ĭ) Allow B to go through several half-lives such that the total amount of time = 2. Find f.ī) Let us set the length of one half-life of A equal to 1. In the same period the number of radio-active nuclei in sample B decreases to a fraction f of the number present initially. In a certain period the number of radio-active nuclei in sample A decreases to one-fourth the number present initially. Problem #26: The half life in two different samples, A and B, of radio-active nuclei are related according to T(1/2,B) = T(1/2,A)/2. ChemTeam: Half-Life Problems #26 - 40 Half-Life Problems #26 - 40 Ten Examples Problems involving carbon-14 Probs 1-10 Problems involving uranium-238 Probs 11-25 Examples and Problems only (no solutions) Return to Radioactivity menu

Half life rule 34