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Hydrometallurgy and leaching

28 questions on Hydrometallurgy and leaching from the Metallurgy chapter: 5 NEET level, 11 JEE Main, 12 JEE Advanced. Each one opens with its answer and solution.

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In Baeyer's process the powdered bauxite is leached with NEET level
When argentite ore is leached with dilute aqueous sodium cyanide in the presence of air, silver passes into solution as NEET level
The metal obtained from the cyanide leach solution of silver or gold is precipitated by adding NEET level
In the electrolytic reduction of alumina, cryolite is added mainly to NEET level
The reaction at the cathode in the Hall-Heroult cell is NEET level
In Baeyer's process the insoluble red residue left after leaching bauxite with hot concentrated NaOH consists mainly of JEE Main level
Assertion (A): Baeyer's process is unsuitable for bauxite that contains a large amount of silica. Reason (R): Red mud, which contains Fe2O3, is formed as a resi... JEE Main level
In Serpeck's process bauxite is heated with coke in a stream of nitrogen to give AlN. Treating AlN with water gives JEE Main level
Sodium aluminate solution is converted into Al(OH)3 in Hall's process by (i) and in Baeyer's process by (ii) . JEE Main level
In the cyanide leaching of gold (4Au + 8NaCN + O2 + 2H2O -> 4Na[Au(CN)2] + 4NaOH), the function of the air bubbled through the pulp is to JEE Main level
A cyanide leach solution contains 4.925 g of gold as Na[Au(CN)2]. Zinc dust is added by the reaction 2Na[Au(CN)2] + Zn -> Na2[Zn(CN)4] + 2Au and 91.0% of the go... JEE Main level
Which statement about the electrolytic refining of impure copper in acidified CuSO4 solution is correct? JEE Main level
In the Parkes process for desilverisation of argentiferous lead, molten zinc is added to molten lead. The process works because JEE Main level
Scrap iron is added to a solution of CuSO4 obtained by acid leaching of a low-grade ore. Given E deg(Cu^2+/Cu) = +0.34 V and E deg(Fe^2+/Fe) = -0.44 V, the stan... JEE Main level
Match the reaction mixture in Column I with a product in Column II. Column I: (P) bauxite with hot conc. NaOH(aq), (Q) argentite with NaCN(aq) and air, (R) cupr... JEE Main level
In the Hall-Heroult cell the graphite anodes have to be replaced periodically because JEE Main level
Select the correct statement(s) about the electrolytic extraction of aluminium. JEE Advanced level
Select the correct statement(s) about the cyanide process for silver and gold. JEE Advanced level
Select the correct statement(s) about the processes used to obtain pure alumina from bauxite. JEE Advanced level
A leach solution contains Ag^+, Cu^2+ and Fe^2+ ions, each at 1 M. Use E deg values (V): Ag+/Ag +0.80; Cu^2+/Cu +0.34; Fe^2+/Fe -0.44; Zn^2+/Zn -0.76. Select th... JEE Advanced level
Select the correct statement(s) about silver recovery and copper refining. JEE Advanced level
In a Hall-Heroult cell 2.70 kg of aluminium (Al = 27) is produced. Taking F = 96500 C/mol, C = 12 and 22.4 L/mol at STP, select the correct statement(s). JEE Advanced level
A 5.52 kg sample of bauxite contains 75.0% Al2O3.2H2O by mass (molar mass 138) and the rest is inert. It is digested as Al2O3 + 2NaOH + 3H2O -> 2Na[Al(OH)4] (wa... JEE Advanced level
A Hall-Heroult cell carries 40.0 kA for 10.0 h with 100% current efficiency. The anode gas is an equimolar mixture of CO and CO2. With F = 96500 C/mol, Al = 27,... JEE Advanced level
24.8 kg of pure argentite, Ag2S (molar mass 248), is leached by Ag2S + 4NaCN -> 2Na[Ag(CN)2] + Na2S. Air oxidises the sulphide formed by 2Na2S + 2O2 + H2O -> Na... JEE Advanced level
194 kg of a zinc ore containing 60.0% ZnS is roasted completely to ZnO (2ZnS + 3O2 -> 2ZnO + 2SO2). The oxide is leached with dilute acid, ZnO + H2SO4 -> ZnSO4 ... JEE Advanced level
A 500.0 g impure copper anode contains 97.0% Cu, 2.0% Zn and 1.0% Ag by mass. It is dissolved completely in an acidified CuSO4 cell with 100% current efficiency... JEE Advanced level
In the Mond process 1.50 kg of crude nickel containing 94.0% Ni is treated with CO at about 330 K: Ni + 4CO -> Ni(CO)4, and the impurities do not react. With Ni... JEE Advanced level