(i) A blackmineral(A) on treatment with dilutesodiumcyanidesolutionin present ofairgivesa clearsolutionof (B) and(C ).(ii) The solutionof (B) on reactionwithzinc givesprecipitate ofametal (D).Identify (A) and (D) andexplainthereactionsofsteps(i) and(ii).

(i) A blackmineral(A) on treatment with dilutesodiumcyanidesolutionin

1.	(i) A blackmineral(A) on treatment with dilutesodiumcyanidesolutionin present ofairgivesa clearsolutionof (B) and(C ).(ii) The solutionof (B) on reactionwithzinc givesprecipitate ofametal (D).Identify (A) and (D) andexplainthereactionsofsteps(i) and(ii).
Answer» Solution :(i) Silver isextanctedfrom its oresbythecyanideprocess. Sincethegivenmineral (A)isblack, itformation ofacomplex, sodiumdicyanoargentate(B). ` ""underset ("A(Black)") +4 NaCNtounderset ("SOD.dicyanorgentate (B)") (2 Na [AG(CN)_2] +Na_2S ` `Na_2 S `THUS formed islargelyoxidisedto` Na_2 SO_ 4`bytheexcess air. `4 Na_2S + 2 H_ 2O+5 O_ 2(air ) tounderset ("Sodium sulphate(C)") (2Na_2SO_4) +4NaOH+2 S` Thus, B is sod. dicyanoargentate and C is sodium sulphate. (ii) Whenthe solutionof B istreated withzinddust, silverbeingless electropositive then zincgetsprecipitated `2 Na [Ag (CN)_2]+ZntoNa_2[ Zn (CN)_4 ] +underset("(D)") ( 2Ag) downarrow `