In fact, due to fluctuations in the carbon amount in the atmosphere, modern C-14 dating needs to be correlated to dates determined by analysis of tree-ring records (dendrochronology). Given a C-14 half-life of 5730 years, you can see that C-14 dating is (theoretically) good out to around 60,000 years (more-or-less). Solution: 1) A common rule of thumb is that a radioactive dating method is good out to about 10 half-lives. Provide two (2) scientifically-based reasons to explain why C-14 dating cannot do this. Problem #49: You read that a fossil dinosaur skull has been found in Montana and that it has been carbon-14 dated to be 73 million years old. Assuming you had a sample of such a tree in which the number of C-14 decay events was 15.3 decays per minute before decomposition, what would the decays per minute be in the present day? Problem #48: Using dendrochronology (using tree rings to determine age), tree materials dating back 10,000 years have been identified. How old is a wooden artifact if it has a count of 9.58 cpm? Problem #47: All current plants have a C-14 count of 15.3 cpm. How many disintegrations per minute per gram of carbon will be measured from a 12900-year-old sample? (The half-life of C-14 is 5730 years.) The observed rate of decay of C-14 from a living plant is 15.3 disintegrations per minute per gram of carbon. Problem #46: A living plant contains approximately the same isotopic abundance of C-14 as does atmospheric carbon dioxide. The half life of carbon-14 is 5730 years. Problem #45: Determine the age of a sample of charcoal which is giving off 25 counts per hour, if carbon-14 from a just made piece of charcoal gives off 85 counts per hour. If a sample today contains 0.060 mg of carbon-14, how much carbon-14 must have been present in the sample 11,430 years ago?ģ) Use a ratio and proportion to find C-14 present in the past: Problem #44: Carbon-14 is used to determine the age of ancient objects.

Problem #43: The C-14 content of an ancient piece of wood was found to have three tenths of that in living trees (indicating 70% of the C-14 had decayed). Another wood sample prepared from an object recovered at an archaeological excavation gives a decay rate of 0.109 disintegration per second per gram of the sample. Problem #42: The carbon-14 decay rate of a sample obtained from a young tree is 0.296 disintegration per second per gram of the sample. What is the age of the piece of wood in years? The decay rate of carbon-14 in fresh wood today is 13.6 counts per minute per gram, and the half life of carbon-14 is 5730 years.ġ) Determine decimal fraction of C-14 remaining:Ģ) Determine how many half-lives have elapsed: Problem #41: A chemist determines that a sample of petrified wood has a carbon-14 decay rate of 6.00 counts per minute per gram. Included in these are two which use C-14 as the example problem to be solved. Note: If you have not looked at the half-life videos on the Radioactivity menu, there are several which measure the drop off in radioactivity in terms of disintegrations. ChemTeam: Half-life problems involving carbon-14 Half-life problems involving carbon-14 Ten Examples Probs 26-40 Probs 1-10 Problems involving uranium-238 Probs 11-25 Examples and Problems only (no solutions) Return to Radioactivity menu

Carbon 14 decay constant