Question

Bromine has two naturally occurring isotopes (br-79 and br-81) and has an atomic mass of

Answer 1

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,

$79.904=(0.49310)(80.9163)+(0.50690)(x)\\79.904=39.89982753+(0.50690)(x)\\40.00417247=(0.50690)(x)\\x=\frac{40.00417247}{0.50690}=\boxed{78.919 \text{ amu}}$