A) boiling impure gold with dil. \[{{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\]
B) boiling impure gold with conc. \[{{H}_{2}}S{{O}_{4}}\]
C) electrolytically
D) Both (b) and (c)
Correct Answer: D
Solution :
Impurities of Cu and Ag from gold are removed by boiling impure gold with cone. \[{{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\] and also by electrolytic method. \[Cu+2{{H}_{2}}S{{O}_{4}}\xrightarrow{\text{heat}}>CuS{{O}_{4}}+S{{O}_{2}}+2{{H}_{2}}O\]\[2Ag+2{{H}_{2}}S{{O}_{4}}\xrightarrow{heat}A{{g}_{2}}S{{O}_{4}}+S{{O}_{2}}+2{{H}_{2}}O\]This method is called parting. Cone. \[\text{HN}{{\text{O}}_{\text{3}}}\]can also be used for this purpose.
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