KCET · Chemistry · General Principles and Processes of Isolation of Metals
In chromite ore, the oxidation number of iron, and chromium are respectively
- A \(+3,+2\)
- B \(+3,+6\)
- C \(+2,+6\)
- D \(+2,+3\)
Answer & Solution
Correct Answer
(D) \(+2,+3\)
Step-by-step Solution
Detailed explanation
Chromite or chrome iron ore is \(\mathrm{FeCr}_{2} \mathrm{O}_{4}\). Its actual composition is \(\mathrm{FeO} \cdot \mathrm{Cr}_{2} \mathrm{O}_{3}\).
In \(\mathrm{FeO}\), oxidation state of \(\mathrm{Fe}\) is calculated as
\[
\begin{aligned}
\mathrm{x}+(-2) &=0 \\
\mathrm{x} &=+2
\end{aligned}
\]
Similarly, in \(\mathrm{Cr}_{2} \mathrm{O}_{3}\), the oxidation state of \(\mathrm{Cr}\) is calculated as
\[
\begin{aligned}
2 \times x+(-2) \times 3 &=0 \\
2 x &=+6 \\
x &=+3
\end{aligned}
\]
In \(\mathrm{FeO}\), oxidation state of \(\mathrm{Fe}\) is calculated as
\[
\begin{aligned}
\mathrm{x}+(-2) &=0 \\
\mathrm{x} &=+2
\end{aligned}
\]
Similarly, in \(\mathrm{Cr}_{2} \mathrm{O}_{3}\), the oxidation state of \(\mathrm{Cr}\) is calculated as
\[
\begin{aligned}
2 \times x+(-2) \times 3 &=0 \\
2 x &=+6 \\
x &=+3
\end{aligned}
\]
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