To calculate the percentage of abundance of each isotope, we can set up a system of equations using the average atomic mass and the atomic masses of the isotopes. Let's assume the abundance of Cl-35 is x (in decimal form) and the abundance of Cl-37 is (1-x) (since the total abundance adds up to 100%).
The average atomic mass can be expressed as:
Average atomic mass = (mass of Cl-35 * abundance of Cl-35) + (mass of Cl-37 * abundance of Cl-37)
Using the given values:
35.453u = (34.968u * x) + (36.956u * (1-x))
Let's solve this equation to find the abundance of Cl-35:
35.453u = 34.968u * x + 36.956u - 36.956u * x
35.453u - 36.956u = -1.988u * x
-1.503u = -1.988u * x
x = -1.503u / -1.988u
x ≈ 0.756
The abundance of Cl-35 is approximately 0.756 (or 75.6%), and the abundance of Cl-37 is approximately 0.244 (or 24.4%).
Therefore, Cl-35 is about 75.6% abundant, and Cl-37 is about 24.4% abundant.