Explain the following: (a) Although Au is soluble in aqua-regia, Ag is not (b) Zinc and hot copper is used for recovery of Ag from the complex [Ag(CN)_(2)]^(-) (c ) Aluminium metal is frequently used as a reducing agent for extraction of metal such as chromium manganese etc. (d) Partial roasting of sulphide ore is donue in the metallurgy of copper.

Explain the following: (a) Although Au is soluble in aqua-regia, Ag i

1.	Explain the following: (a) Although Au is soluble in aqua-regia, Ag is not (b) Zinc and hot copper is used for recovery of Ag from the complex [Ag(CN)_(2)]^(-) (c ) Aluminium metal is frequently used as a reducing agent for extraction of metal such as chromium manganese etc. (d) Partial roasting of sulphide ore is donue in the metallurgy of copper.
Answer» Solution :(a) Au dissolved in aquaregia forming soluble `HAuCl_(4)` but Ag forms insoluble AgCl `Au + 4HCl + 3HNO_(3) to underset("soluble")(HAuCl_(4)) + 3NO_(2) + 3H_(2)O` `Ag + HCl + HNO_(3) to underset("insoluble")(AgCl) + NO_(2) + H_(2)O` (b) Zinc is POWERFUL reducing agent in comparison to copper and zinc is cheaper also than copper. (C ) Aluminium metal is frequently used as a reducing agent for the EXTRACTION of metals. Such as Cr and Mn from their respective oxides because aluminium is more electropositive than Cr or Mn. The process of reduction is called alumino thermy. `Cr_(2)O_(3) + 2Al to Al_(2)O_(3) + 2Cr` `3Mn_(2)O_(4) + 8Al to 4Al_(2)O_(3) + 9Mn` (d) Partial roasting of sulphide ore forms some oxide. The oxide then reduces the remaining sulphide ore into metal. `2CuS + 3O_(2) to 2CuO + 2SO_(2)` `2CuO + CUS to 3Cu^(+) + SO_(2)`