Question

Bromine has two isotopes 79Br and 81Br, whose masses (78.9183 and 80.9163 amu) and abundances (50.69% and 49.31%, respectively) were determined in earlier experiments. Calculate the average atomic mass of bromine based on these experiments.

Answer 1

Average atomic mass = 79.9034 amu

Step-by-step explanation:

The formula for the calculation of the average atomic mass is:

`Average\ atomic\ mass=(\frac {\%\ of\ the\ first\ isotope}{100}* {Mass\ of\ the\ first\ isotope})+(\frac {\%\ of\ the\ second\ isotope}{100}* {Mass\ of\ the\ second\ isotope})`

Given that:

For first isotope:

% = 50.69 %

Mass = 78.9183 amu

For second isotope:

% = 49.31 %

Mass = 80.9163 amu

Thus,

`Average\ atomic\ mass=(50.69)/(100)* {78.9183}+(49.31)/(100)* {80.9163}\ amu`

`Average\ atomic\ mass=40.0036+39.8998\ amu`

Average atomic mass = 79.9034 amu