The following reactions take place in the blast furnace in the preparation of impure iron. Identify the reaction pertaining to the formation of the slag.

• Fe₂O₃ (s) + 3CO (g) → 2 Fe (l) +3CO₂ (g)

• CaCO₃ (s) → CaO (s) + CO₂ (g)

• CaO (s) +SiO₂ → CaSiO₃ (s)

• CaO (s) +SiO₂ → CaSiO₃ (s)

Which of the following statements, about the advantage of roasting of sulphide ore before reduction is not true?

• Carbon and hydrogen are suitable reducing agent for metal sulphides

• The Δ_fG^o of the sulphide is greater than those for CS₂ and H₂S

• The Δ_fG^o  is negative for roasting of sulphide ore to oxide

• The Δ_fG^o  is negative for roasting of sulphide ore to oxide

Sulphide ores of metals are usually concentrated by froth flotation process. Which one of the following sulphide ores offers an exception and is concentrated by chemical leaching?

• Argentite

• Galena

• Copper pyrite

• Copper pyrite

164.

Copper sulphates dissolves in excess of KCN to give:

• CuCN

• [Cu(CN)₄]^3-

• [Cu(CN)₄]^2-

• [Cu(CN)₄]^2-

Al₂O₃ can be converted to anhydrous AlCl₃ by heating:

• Al₂O₃ with HCl gas

• Al₂O₃ with NaCl in solid state

• a mixture of Al₂O₃ and carbon in dry Cl₂ gas

• a mixture of Al₂O₃ and carbon in dry Cl₂ gas

Extraction of gold and silver involves leaching with CN– ion. Silver is later recovered by

• Liquation

• Distillation

• Zone refining

• Zone refining

Extraction of gold and silver involves leaching with CN^– ion. Silver is later recovered by

• Liquation

• Distillation

• Zone refining

• Zone refining

Considering the Ellingham diagram, which of the following metals can be used to reduce alumina?

• Fe

• Zn

• Cu

• Mg

In cyanide extraction process of silver from argentite ore, the oxidising and reducing agents are respectively.

• O₂ and CO₂

• O₂ and Zn dust

• HNO₃ and Zn dust

• HNO₃ and CO

Flux is used to 

• remove all type of impurities

• reduce metal oxide

• remove carbonate and sulphate

• remove silica and undesirable metal oxides