Some Basic Concepts of Chemistry - Result Question 13
20. Given that the abundances of isotopes ${ }{54} \mathrm{Fe},{ }{56} \mathrm{Fe}$ and ${ }_{57} \mathrm{Fe}$ are $5 %, 90 %$ and $5 %$, respectively, the atomic mass of Fe is
(2009)
(a) 55.85
(b) 55.95
(c) 55.75
(d) 56.05
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Answer:
Correct Answer: 20. (b)
Solution:
- From the given relative abundance, the average weight of Fe can be calculated as
$A=\frac{54 \times 5+56 \times 90+57 \times 5}{100}=55.95$
BETA
