alleryAn element has two isotopes: one of mass 9 amu (50% abundance) and another of mass 10 amu (50% abundance). What is its average atomic mass?
A9.0 amu
B10.0 amu
C19.0 amu
D9.5 amu
Answer & Solution
Correct answer: D. 9.5 amu
1. Convert percentages to fractions: $0.50$ and $0.50$.
2. Average atomic mass $= (9 \times 0.50) + (10 \times 0.50)$.
3. $= 4.5 + 5 = 9.5$ amu.
_Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 7 Atoms and Molecules "Average Atomic Mass", p.100_
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