please help me as I can't understand how to figure out this question...
(a) Many elements exhibit variable oxidation numbers. The oxidation numbers of copper are 0, +1 and +2.
The element copper is present in many metallic minerals. These minerals include chalcopyrite (CuFeS2), malachite (Cu2(CO3)(OH)2), and copper metal (Cu).
(i) State the oxidation number of copper in copper metal (Cu)
(ii) Determine the oxidation number of copper in malachite, Cu2(CO3)(OH)2. Include your working to show how the oxidation number was determined.
(iii) Sulfur has an oxidation number of –2 in chalcopyrite, CuFeS2.
Discuss the possible oxidation numbers of both copper and iron in chalcopyrite, CuFeS2.
(b) Copper ores that contained the compound copper(II) sulfide, CuS, were first mined by ancient miners. First they roasted the CuS in air as shown by Equation A. Then the product was reacted with carbon as shown by Equation B.
Roasting in air: 2CuS + 3O2 → 2CuO + 2SO2 Equation A
Reacting the product with carbon: CuO + C → Cu + CO Equation B
Both these reactions are examples of redox equations.
(i) In Equation A circle the element which is oxidised.
(ii) Justify your answer.
(iii) In terms of oxidation number, explain why Equation B is a redox reaction.