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Indicate the steps in the preparation of:
(i) \(\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7\) from chromite ore
(ii) \(\mathrm{KMnO}_4\) from pyrolusite ore.
(i) \(\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7\) from chromite ore
(ii) \(\mathrm{KMnO}_4\) from pyrolusite ore.
Solution:
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Verified Answer
(i) \(4 \mathrm{FeCr}_2 \mathrm{O}_4+8 \mathrm{Na}_2 \mathrm{CO}_3+7 \mathrm{O}_2 \rightarrow\)
\(\begin{aligned}
8 \mathrm{Na}_2 \mathrm{CrO}_4+2 \mathrm{Fe}_2 \mathrm{O}_3+8 \mathrm{CO}_2 \\
2 \mathrm{Na}_2 \mathrm{CrO}_4+2 \mathrm{H}^{+} \rightarrow \mathrm{Na}_2 \mathrm{Cr}_2 \mathrm{O}_7+2 \mathrm{Na}^{+}+\mathrm{H}_2 \mathrm{O} \\
\mathrm{Na}_2 \mathrm{Cr}_2 \mathrm{O}_7+2 \mathrm{KCl} \rightarrow \mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7+2 \mathrm{NaCl}
\end{aligned}\)
(ii) \(2 \mathrm{MnO}_2+4 \mathrm{KOH}+\mathrm{O}_2 \stackrel{\Delta}{\longrightarrow} 2 \mathrm{~K}_2 \mathrm{MnO}_4+2 \mathrm{H}_2 \mathrm{O}\)
\(\begin{aligned}
8 \mathrm{Na}_2 \mathrm{CrO}_4+2 \mathrm{Fe}_2 \mathrm{O}_3+8 \mathrm{CO}_2 \\
2 \mathrm{Na}_2 \mathrm{CrO}_4+2 \mathrm{H}^{+} \rightarrow \mathrm{Na}_2 \mathrm{Cr}_2 \mathrm{O}_7+2 \mathrm{Na}^{+}+\mathrm{H}_2 \mathrm{O} \\
\mathrm{Na}_2 \mathrm{Cr}_2 \mathrm{O}_7+2 \mathrm{KCl} \rightarrow \mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7+2 \mathrm{NaCl}
\end{aligned}\)
(ii) \(2 \mathrm{MnO}_2+4 \mathrm{KOH}+\mathrm{O}_2 \stackrel{\Delta}{\longrightarrow} 2 \mathrm{~K}_2 \mathrm{MnO}_4+2 \mathrm{H}_2 \mathrm{O}\)
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