Answer to Question #141978 in General Chemistry for Learner

Question

Compute the average atomic mass of gallium, if 60.0% of the gallium atom occurring in nature have mass number 69 and 40.0% of the items have mass number 71.

Answer 1

The isotopes of gallium with mass numbers of 69 and 71 have abundances of 60.0% and 40.0% , respectively. In order to calculate the average atomic mass of gallium, one needs to (i) convert the percentages to fractions (divide the percentage by 100) and (ii) sum up the products of the fractions and mass numbers $f·A_i$ .

Therefore, the average atomic mass of gallium can be calculated as:

$A = \frac{60.0}{100}·69 + \frac{40}{100}·71 = 69.8$ amu.

Answer: the average atomic mass of gallium, if 60.0% of the gallium atom occurring in nature have mass number 69 and 40.0% of the items have mass number 71 is 69.8 amu.