Question

The oxidation states of Cu and Fe in copper pyrites is respectively:
A.+1 and +2
B.+2 and +3
C.+1 and +3
D.+2 and +6

Answer 1

Hint: The principle ore of copper is Copper pyrite. The chemical formula for copper pyrite is $ {\text{CuFe}}{{\text{S}}_{\text{2}}}$.It is also known as Chalcopyrite.

Complete step by step answer:
The copper iron sulfide mineral is Chalcopyrite. The name is derived from Greek word “chalkos” meaning copper, “pyrites” meaning striking fire. It is a tetragonal system. The chemical formula of the tetragonal system is ${\text{CuFe}}{{\text{S}}_{\text{2}}}$.These minerals can be concentrated by Froth floatation process, gravity separation, distillation and fractionation.
The oxidation state of copper is +1 while the oxidation state of iron is +3. ${\text{F}}{{\text{e}}^{{\text{3 + }}}}$ and ${\text{C}}{{\text{u}}^{{\text{2 + }}}}$ ions are arranged alternatively in tetragonal structure. Whereas the oxidation state of Sulphur (S) is -2. The oxidation states were determined by various computational spectroscopic methods. In the crystal structure, each metal ion is tetrahedrally coordinated to 4 sulphur anions. Each sulphur anion is bonded to two copper atoms and two iron atoms.

So, the correct option is C.

Additional information:
 By roasting a mixture of chalcopyrite and silica sand, Copper metal can be extracted. It can be as shown by the following reaction:
\[{\text{2CuFe}}{{\text{S}}_{\text{2}}}{{\text{}}_{\left( {\text{s}} \right)}}{\text{ + 5}}{{\text{O}}_{{\text{2}}\left( {\text{g}} \right)}}{\text{ + 2Si}}{{\text{O}}_{{\text{2}}\left( {\text{s}} \right)}} \rightleftharpoons {\text{2C}}{{\text{u}}_{\left( {\text{l}} \right)}}{\text{ + 4S}}{{\text{O}}_{{\text{2}}\left( {\text{g}} \right)}}{\text{ + 2FeSi}}{{\text{O}}_{{\text{3}}\left( {\text{l}} \right)}}\]
Unlike pyrite mineral, chalcopyrite has single \[{{\text{S}}^{{\text{2 - }}}}\]sulphide ions rather than pairs. Elements such as Ag, Au, Cd, Co, Ni, Pb, Sn, and Zn can be found in minor amounts that can be measured in part per million levels.

Note:
The crystallographic structure of chalcopyrite is closely related to that zinc ore, namely Zinc blende (ZnS). It is simply the replacement of \[{\text{Z}}{{\text{n}}^{{\text{2 + }}}}\]ions by \[{\text{F}}{{\text{e}}^{{\text{3 + }}}}\]ions. Chalcopyrite is also known as “yellow copper” due to its appearance.