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I have three chem questions that I need help on?
1. Three isotopes of Argon-36(35.97 amu, 0.337%), Argon-38 (37.96 amu, 0.063%) and Argon-40 (39.96 amu, 99.600%). Find the atomic mass of Argon.
The other two questions are like this one, could someone please demonstrate how to do it so I can apply the method to the others? Thank you!
2 Answers
- Trevor HLv 71 decade agoFavorite Answer
You have to use a mathematical technique called " weighted average " to get the answer. This is not at all difficult.
Argon 36 = 35.97 * 0.337 = 12.12189
Argon 38 = 37.96 * 0.063 = 2.39148
Argon 40 = 39.96 * 99.6 = 3,980.016
Add all these values up:
Total = 3,994.53
Divide total by 100
Atomic mass = 39.9453 amu
Easy - when you know how. Do the rest in exactly the same way.
- kumorifoxLv 71 decade ago
It's quite simple.
First, convert the percentage to a decimal (divide by 100). So the abundance of argon-36 is 0.337/100 = 0.00337, argon-38 is 0.063/100 = 0.00063 and argon-40 is 0.99600.
Next, multiply the atomic mass of each isotope by its decimal abundance, then add those values together to get the atomic mass of argon.
(35.97Ã0.00337) + (37.96Ã0.00063) + (39.96Ã0.99600) = 0.1212189 + 0.0239148 + 39.80016 = 39.9452937 = 39.95 AMU, correct to 4 significant figures.
