Question 2.1.2: Calculate the average atomic weight for chlorine. Chlorine h......
Calculate the average atomic weight for chlorine. Chlorine has two naturally occurring isotopes, chlorine-35 (34.96885 u, 75.78% abundant) and chlorine-37 (36.96590 u, 24.22% abundant).
You are asked to calculate the average atomic weight for chlorine.
You are given the relative abundance of the chlorine isotopes and the exact mass of each isotope.
Use Equation 2.1, the exact mass of the isotopes, and the fractional abundance of the isotopes to calculate the average atomic weight of chlorine.
average atomic weight = \sum\limits_{\; \text{all}\\\text{istopes}}{} (exact mass) (fractional abundance) (2.1)
average atomic weight (Cl) = (^{35}Cl exact mass)(^{35}Cl fractional abundance)
+ (^{37}Cl exact mass)(^{37}Cl fractional abundance)
average atomic weight (Cl) = (34.96885 u)\left(\frac{75.78}{100} \right) + (36.96560 u)\left(\frac{24.2}{100} \right)
average atomic weight (Cl) = 35.45 u
Is your answer reasonable? The average mass of chlorine should be closer to 35 u than 37 u because the chlorine-35 isotope is more abundant than the chlorine-37 isotope.