Answer
:
87.62 u
Explanation:
The atomic mass of Sr is the weighted average of the atomic masses of its isotopes.
We multiply the atomic mass of each isotope by a number representing its relative importance (i.e., its percent of the total).
Set up a table for easy calculation
0.0050 × 83.91 u = 0.420 u
0.099 × 85.91 u = 8.505 u
0.070 × 86.91 u = 6.084 u
0.826 × 87.91 u = 72.61 u
TOTAL = 87.62 u
