Question

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1.
One chlorine isotope with 18 neutrons has an abundance of 75.77% and a mass number of 35 amu.
The other chlorine isotope has 20 neutrons, an abundance of 24.23% and a mass number of 37 amu.
What is the average atomic mass?

Answer 1

Answer: 35.4846 amu

Explanation: Hey! To find the average atomic mass of an element's isotopes here are the steps

1. Take the relative abundance of the chlorine isotope with the mass of 35 amu, this is 75.77, and divide by 100, 0.7577

Multiply that with the mass, 35 amu, (35 amu x 0.7577) = 26.5195

2. Do the same with the other isotope with a mass of 37 amu

Divide the relative abundance by 100, 24.23/100 = 0.2423

Multiply 0.2423 by 37, that will be 8.9651.

Add the two answers (26.5195 + 8.9651) = 35.4846 amu

And there's your answer!