Answer:
C. 114.8 u
Explanation:
The atomic mass of X 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
0.0429 × 112.90 u = 4.843 u
0.9571 × 114.90 u = 109.97 u
TOTAL = 114.8 u
