Explanation:
Average atomic mass of Chlorine = 35.45 amu
The percentage of isotopes is the percentage abundance.
This is given by;
Average atomic mass = (Mass of isotope * Percentage abundance of 35/17 Cl) + (Mass of isotope * Percentage abundance 37/17 Cl)
Let percentage abundance of 35/17 Cl = x
Then percentage abundance of 37/17 Cl = 1 - x
Putting the values in the equation;
35.45 = (35 * x) + (37 * (1-x))
35.45 = 35x + 37 - 37x
35.45 - 37 = 35x - 37x
- 1.55 = -2x
x = 1.55 / 2 = 0.775
Percentage abundance of 35/17 Cl = 0.775 * 100 = 77.5%
Percentage abundance of 37/17 Cl = (1 - 0.775) * 100 = 22.5%
