Bromine has two naturally occurring isotopes (br-79 and br-81) and has an atomic mass of
79.904 amu. the mass of br-81 is 80.9163 amu, and its natural abundance is 49.310%. what is
the mass of br-79?

Respuesta :

Answer: 78.919 amu

Explanation:

If the natural abundance of Br-81 is 49.310%, then the natural abundance of Br-79 must be 100%-49.310%=50.690%

Substituting into the atomic mass formula,

[tex]79.904=(0.49310)(80.9163)+(0.50690)(x)\\79.904=39.89982753+(0.50690)(x)\\40.00417247=(0.50690)(x)\\x=\frac{40.00417247}{0.50690}=\boxed{78.919 \text{ amu}}[/tex]