Question

Q6. Bromine, like chlorine, has two stable isotopes. For bromine, the isotopicmasses are 78.9183 amu, with a relative abundance of 50.69% and 80.9163amu with a relative abundance of 49.31%. Calculate the average atomic weightof bromine.

Answer 1

The question requires us to calculate the average atomic weight of bromine, given this element isotope masses and their abundance.

The following information was provided by the question:

number of isotopes of Br = 2

mass of isotope 1 = m1 = 78.9183 amu

abundance of isotope 1 = f1 = 50.69%

mass of isotope 2 = m2 = 80.9163 amu

abundance of isotope 2 = f2 = 49.31%

The average atomic mass of an element is the sum of the masses of its isotopes, each multiplied by its natural abundance (we use the decimal number associated with the abundance for the isotope; for example: if the abundance is 75%, we use 0.75).

Therefore, to calculate the average atomic mass of Br, we'll use the following equation:

`\text{average mass Br = m}_1* f_1+m_2* f_2`

where m refers to the isotope mass and f, to its natural abundance.

Applying the values provided by the problem, we have:

`\text{average mass Br = (}78.9183*0.5069_{})+(80.9163*0.4931)=79.90\text{ amu}`

Therefore, the average atomic weight of bromine is 79.90 amu.