1. Tardigrade
  2. Question
  3. Chemistry
  4. The nonstoichiometric oxide of iron called wustite has empirical formula Fe x O. It has a density of 5.75 g / cm 3, a cubic unit cell with cell constant of 431 pm and an FCC arrangement of oxygen atoms. Find the fraction Fe(II) in total iron.

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Q. The nonstoichiometric oxide of iron called wustite has empirical formula $Fe _{ x } O$. It has a density of $5.75 \,g / cm ^{3}, a$ cubic unit cell with cell constant of $431 \,pm$ and an $FCC$ arrangement of oxygen atoms. Find the fraction $Fe(II)$ in total iron.

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Solution:

$5.75=\frac{(56 x+16) 4}{\left(4.31 \times 10^{-8}\right)^{3} \times 6.02 \times 10^{23}} $
$\Rightarrow x=0.95$
Using charge balance we write for $z$ moles of $+2$ and rest $+3$ iron.
$2(z)+3(0.95-z)=2 $
$\Rightarrow 2 z+2.85-3 z=2$
$\Rightarrow z=0.85$
$\therefore $ fraction is $ \frac{0.85}{0.95}=0.895$