Given, that the abundances of isotopes, ${ }^{54} \mathrm{Fe},{ }^{56} \mathrm{~F}$ and ${ }^{57}…

Given, that the abundances of isotopes, ${ }^{54} \mathrm{Fe},{ }^{56} \mathrm{~F}$ and ${ }^{57} \mathrm{Fe}$ are $5 \%$, $90 \%$ and $5 \%$, respectively, the atomic mass of $\mathrm{Fe}$ is
  1. $55.85$
  2. $55.95$
  3. $55.75$
  4. $56.05$

Solution

Average atomic weight $ \frac{54 \times 5+56 \times 90+57 \times 5}{100}=55.95 $

Asked in: JEE Advanced 2009 (Paper 1)

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