In which of the following process oxidation state of metal present in ore is changed from +3 to 0
(i) Hematite $+ Al Δ$
(ii) Gold ore $+ NaCN_{(aq.)} air$
(iii) Red Bauxite $+ NaOH_{(aq.)} \to$
(iv) Cassitarite $+ C / CO Δ$
(v) Allumina (molten) $El ec t ro l ys i s$

(vi)Limonite $Δ in the absence of oxygen$

Question

In which of the following process oxidation state of metal present in ore is changed from +3 to 0

(i) Hematite $+ Al Δ$

(ii) Gold ore $+ NaCN_{(aq.)} air$

(iii) Red Bauxite $+ NaOH_{(aq.)} \to$

(iv) Cassitarite $+ C / CO Δ$

(v) Allumina (molten) $El ec t ro l ys i s$

(vi)Limonite $Δ in the absence of oxygen$

TestHub · Accepted Answer

The oxidation state of the metal changes from +3 to 0 in processes (i) and (v).

(i) Hematite (Fe₂O₃) + Al: Fe from +3 to 0 (Thermite process).

(v) Alumina (Al₂O₃) electrolysis: Al from +3 to 0 (Hall-Héroult process).

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