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Practice each question, then open the answer or worked solution.
The purest form of iron is prepared by oxidising impurities from cast iron in a reverberatory furnace. Which iron ore is used to line the furnace? Explain by giving a reaction.
Haematite ore (Fe2O3) is the iron ore used to line the reverberatory furnace.
Fe2O3 + 3 C → 2 Fe + 3CO
Haematite is reduced by coke to wrought iron and the coke gets oxidised to CO.
The mixture of compounds A and B is passed through a column of Al2O3 by using alcohol as eluant. Compound A is eluted in preference to compound B. Which of the compounds A or B, is more readily adsorbed on the column?
Compound A doesn’t adsorb on the column well and moves down the column with alcohol (eluant), while compound B gets adsorbed well on the column and cannot move down.
Why is sulphide ore of copper heated in a furnace after mixing with silica?
Sulphide ore of copper is heated in a furnace after mixing with silica because the iron impurities present in the ore can form slag with silica and will be easily removed. The copper is produced as copper matte.
FeO + SiO2→ FeSiO3(slag)
Why are sulphide ores converted to oxide before reduction?
Sulphide ores cannot be easily reduced so they are usually converted to oxides because oxides can be reduced easily.
Which method is used for refining Zr and Ti? Explain with the equation.
Van Arkel method is used for refining Zr and Ti. Van Arkel process involves heating the impure metal with Iodine. It forms a volatile complex which on decomposition at high temperatures, gives back the metal but in very pure form.
Refining of Zr and Ti using Van Arkel method
For Zirconium,
Zr(impure) + 2I2→ ZrI4
ZrI4→Zr(pure) + 2I2 (at 1800K)
For Titanium,
Ti(impure) + 2I2→ TiI4
TiI4 → Ti(pure) + 2I2 (at 1800K)
What should be the considerations during the extraction of metals by electrochemical method?
(i) Reactivity of the metal produced
(ii) Electrodes to be made of suitable material
(iii) Addition of flux for making molten mass conducting
What is the role of flux in metallurgical processes?
To remove gangue, certain substances are mixed with it. These are called fluxes. Flux can be basic or acidic. Acidic flux removes basic impurity and basic flux removes acidic impurity. Flux is also used for increased conductivity.
How are metals used as semiconductors refined? What is the principle of the method used?
Semiconductors are refined by zone refining. Zone refining is based on the principle that impurities are more soluble in the molten metal than in the solid metal. A molten zone moves along the impure rod heating it, the impurities dissolve in the molten zone and move along the rod, while the pure metal devoid of impurities gets left behind and crystallises out.
Write down the reactions taking place in Blast furnace-related to the metallurgy of iron in the temperature range 500-800 K.
These are the reactions that happen in the blast furnace at the 500K-800K range.
3Fe2O3 + CO → 2Fe3O4 + CO2
Fe3O4 + CO →3FeO + 2CO2
Fe2O3 + CO → 2FeO + CO2
Give two requirements for vapour phase refining.
(i) The metal should react easily with the reagent to form the complex.
(ii) The volatile complex should easily decomposable so that the recovery is easy.