Start by ignoring a few chemical realities and assume all the Ra-226 ends up as lead.Д¦.80 g / 205.974465 g/mol = 0.033013801 mol of Pb-206 decayedД«) Calculate grams of Ra-226 initially present: Chemical analysis of a certain chunk of concrete from an atomic-bombed city, preformed by an archaeologist in the year 6264 AD, indicated that it contained 2.50 g of Ra-226 and 6.80 g of Pb-206. Problem #30: The isotope Ra-226 decays to Pb-206 in a number of stages which have a combined half-life of 1640 years. If the half life of tritium is 12.25 years, calculate the actual number of tritium atoms remaining in 10.0 g water after a period of 49 years. Problem #29: The ratio of tritium, H-3, to hydrogen, H-1, in a sample of water was 1:1x10 19. Solution: A has a half-life of 3 hrs, so 18 hrs = 6 half-lives.Д« has a half-life of 6 hrs, so 18 hrs = 3 half-lives.ДЄfter 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.Д¬) Allow B to go through several half-lives such that the total amount of time = 2. Find f.Д«) 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