Explainthe following :(i) Zincbutnot copperis usedfortherecoveryofAg from [Ag(CN)""_(2)]^(-) (ii) Partialroasting ofsulphide ore isdoneinthe metallurgyof copper. (iii) Why ischalcociteroasted and notcalcinedduringextractionof copper ?

Explainthe following :(i) Zincbutnot copperis usedfortherecoveryofAg f

1.	Explainthe following :(i) Zincbutnot copperis usedfortherecoveryofAg from [Ag(CN)""_(2)]^(-) (ii) Partialroasting ofsulphide ore isdoneinthe metallurgyof copper. (iii) Why ischalcociteroasted and notcalcinedduringextractionof copper ?
Answer» Solution :(i) The ` E^(@) `ofzinc` (Zn^( 2 +) //Zn =- 076 V) `is lower than thatofcopper` (Cu^( 2 +)//Cu=034V)`,therefore, Zn ISA morepowerfulreducing agent Cu . Further , Zn is also cheaper than Cu. Because of these two reasons , zinc but not copper is used for the recovery of silver from `[Ag(CN)_(2)]^(-)`. (ii) Partial roasting of sulphide ore forms some oxide which then reacts with the remaining sulphide ore to form copper metal by self-reducing of the oxide and sulphide . `2Cu_(2) S + 3 O_(2) to 2 Cu_(2) O + 2 SO_(2)` , `2 Cu_(2)O + Cu_(2) S to 6 Cu + SO_(2)` Thus , to bring about self reducing process , sulphide ore of copper is partially roasted . (III) Calcination is used for conversion of carbonate and HYDROXIDE ores to their respective oxides while roasting is used for conversion of sulphide ores to their respective oxides . SINCE chalcocite `(Cu_(2)S)` is a sulphide ore , therefore , it is roasted and not calcined .