111.

Gold is extracted by hydrometallurgical process, based on its property

• of being electropositive

• of being less reactive

• to form complexes which are water soluble

• to form salts which are water soluble

Which of the following taking place in the blast furnace is endothermic?

• CaCO₃ → CaO + CO₂

• 2C + O₂ → 2CO

• C + O₂ → CO₂

• Fe₂O₃ + 3CO → 2Fe + 3CO₂

During the extraction of gold the following reactions take place

Au + CN^- + H₂O $\stackrel{{\mathrm{O}}_2}{\to }$ [X]

             [X] + Zn → [Y] + Au

X and Y are respectively

• [Au(CN)₂]^- and [Zn(CN)₆]^4-

• [Au(CN)₄]^2- and [Zn(CN)₄]^2-

• [Au(CN)₄]^3- and [Zn(CN)₄]^2-

• [Au(CN)₂]^- and [Zn(CN₄)]^2-

Identify the ore not containing iron.

• limonite

• siderite

• carnallite

• chalcopyrites

Identifythe reaction that does not take place in a blast furnace

• CaCO₃ → CaO + CO₂

• CaO + SiO₂ → CaSiO₃

• 3Fe₂O₃ + 3C → 4Fe+ 3CO₂

• CO₂ + C → 2CO

The ore that is concentrated by froth floatation process is

• zincite

• cinnabar

• bauxite

• malachite

In the electrolytic refining of zinc

• graphite is at the anode

• the impure metal is at the cathode

• the metal ion get reduced at the anode

• acidified zinc sulphate is the electrolyte

The temperature of the slag zone in the metallurgy of iron using blast furnace is

• 1200 - 1500°C

• 1500 - 1600 °C

• 400 - 700°C

• 800 - 1000°C

Which one of the following statements is false?

• During roasting, moisture is removed from the ore

• The ore is freed from almost all non-metallic impurities

• Calcination of ore is carried out in the absence of any blast of air

• The concentrated zinc blende is subjected to calcination during its extraction by pyrometallurgy

The process of zone refining is used in the purification of

• Al

• Ge

• Cu

• Ag