\(\mathrm{Cr}_2 \mathrm{P}_7^{2 \cdot}+6 \mathrm{Fe}^{2+} \rightarrow 2 \mathrm{Cr}^{3+}+6 \mathrm{Fe}^{3+}+7 \mathrm{H}_2 \mathrm{O}\). In the equation above, the oxidation number of chromium changes from \((\)
A. \(+7\) to \(++3\) B. \(+6\) to \(+3 \) C. \(-6\) to \(+3 \) D. \(-2\) to \(+6\)
Correct Answer: B
Explanation
\(\mathrm{Cr}_2 \mathrm{O}_7^{2-}+6 \mathrm{Fe}^{2+} \rightarrow 2 \mathrm{Cr}^{3+}+6 \mathrm{Fe}^{3+}+7 \mathrm{H}_2 \mathrm{O}\) The oxidation number of chromium in heptaoxodichromate (VI) ion is +6. Thus. there is a shift from \(+6\) to \(+3\).