Potassium-Argon dating is a common method of determining the age of rocks based on the time they were last liquified, and thus we can determine the age of a surface by examining the ratio of the parent K40 to the decay product Ar40. This works because argon is a gas, which will be free to bubble out of liquified rock whenever the rock is hot enough to no longer be in it's solid state (think of magma covering a surface). This means that just after the rock solidifies, there should be effectively no Ar40 remaining and that any Ar40 that we do find in the rock at the time of the collection of the sample must be due to radioactive decay. With all of this in mind, if we find that a rock sample has 31 Ar40 atoms for every 1 K40 atom, and the half-life of K40 is 1.3 billion years, how much time has passed in years since that rock was geologically active (aka it was last liquified)?  When typing your answer, please do not use commas or scientific notation because of how Blackboard interprets numerical answers. For example, you would type 1300000000 rather than 1.3*10^9 or 1,300,000,000

Chemistry: An Atoms First Approach
2nd Edition
ISBN:9781305079243
Author:Steven S. Zumdahl, Susan A. Zumdahl
Publisher:Steven S. Zumdahl, Susan A. Zumdahl
Chapter18: The Nucleus: A Chemist's View
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Potassium-Argon dating is a common method of determining the age of rocks based on the time they were last liquified, and thus we can determine the age of a surface by examining the ratio of the parent K40 to the decay product Ar40. This works because argon is a gas, which will be free to bubble out of liquified rock whenever the rock is hot enough to no longer be in it's solid state (think of magma covering a surface). This means that just after the rock solidifies, there should be effectively no Ar40 remaining and that any Ar40 that we do find in the rock at the time of the collection of the sample must be due to radioactive decay.

With all of this in mind, if we find that a rock sample has 31 Ar40 atoms for every 1 K40 atom, and the half-life of K40 is 1.3 billion years, how much time has passed in years since that rock was geologically active (aka it was last liquified)? 

When typing your answer, please do not use commas or scientific notation because of how Blackboard interprets numerical answers. For example, you would type 1300000000 rather than 1.3*10^9 or 1,300,000,000

 
 
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