Question

Chlorine has two isotopes. Chlorine-35 has an actual mass of 34.9689 u and chlorine-37 has a mass of 36.9659 u. In any sample of chlorine atoms, 75.771% will be chlorine-35 and 24.229% will be chlorine 37. Calculate the average atomic mass of chlorine. 2. Copper has two isotopes. Copper-63, which has an atomic mass of 62.93 u and copper-65, which has an atomic mass of 64.93 u. In any sample of copper atoms, 69.1% will be copper-63 and 30.9% will be copper-65. Calculate the average atomic mass of naturally occurring copper.

Answer 1

Answer: 1. The average atomic mass of chlorine is 35.453u

2. The average atomic mass of copper is 63.5 u

Explanation:

Average atomic mass is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

$\text{Average atomic mass }=\sum_{i=1}^n\text{(Atomic mass of an isotopes)}_i\times \text{(Fractional abundance})_i$

1. For chlorine:

$\text{Average atomic mass of chlorine }=(34.9689\times \frac{75.771}{100})+(36.9659\times \frac{24.229}{100})=35.453u$

2.  For copper:

$\text{Average atomic mass of chlorine }=(62.93\times \frac{69.1}{100})+(64.93\times \frac{30.9}{100})=63.5u$