Revisal Problems (Past 13 Year) JEE Main (Metallurgy) - Class 12 MCQ

Metals like Na, K, Mg, Ca, Al extracted by the electrolysis of their salts in molten state. This is called electrometallurgy.

Leaching This method consists in treating the powdered ore with a suitable reagent (acids, bases or other chemicals) which can selectively dissolve the ore but not the impurities.

Chalcocite = Copper glance = CU₂S.

CaCO₃ → CaO + CO₂,CaO + SiO₂ (slag)

Zone refining is based on the principle that the impurities are more soluble in the melt than in the solid state of the metal.

Manganese steel, an alloy of exceptional durability that found uses in the construction of railroad rails and rock-crushing machinery. Manganese steel containing 12-14 per cent manganese, it provides a hard, wear-resistant etc.

CuO, K₂O cannot be reduced to give respective metals.

The reduction process is accompanied by an increase in volume and is therefore facilitated when implemented under reduced pressure condition. Hence, ΔG is positive.

The major impurities in bauxite are iron oxides (haematite), silicon dioxide.

Fluorspas (CaF₂) is used to lower the temperature of the melt. It is also used to increase the conductivity of the mixture.

2AI + Fe2O₃ → AI₂O₃ + 2Fe

Cyanide process Extraction of Au, Ag

Heavy spar is BaSO₄, Anglesite = PbCO₃
Cerussite = PbSO₄, Galena = PbS

Spiegeleisen is a ferromanganese alloy containing approximately 15% manganese and small quantities of carbon and silicon. Historically, this was the standard form in which manganese was traded and used in steel making.
Being remarkably free from impurities, such as phosphorus, sulphur, and silica, it was much used in the Bessemer process for the purpose of reintroducing carbon. It reduces the iron oxide and is itself subject to oxidation.

Argentite (Ag₂S) is sulphide and cuprite are oxides.

The molten mixture of Al₂O₃ and Na₃AIF₆ used as an electrolyte.

Aqueous solution of calcium chloride upon electrolysis give calcium hydroxide because calcium metal reacts with water to produce calcium hydroxide.

Hydrometallurgy is the process of bringing the metal into solution by the action of suitable chemical reagents (NaCN solution or chlorine in water etc.) followed by recovery of the metal by the use of proper precipitating agent which is a more electropositive metal.

Argentiferrous lead contain upto 2% silver in it. To remove such silver in lead in desilverisation methods are used like Parke’s and Pattinson's process. In this zinc is added which combine with Ag forming zinc-silver alloy which is lighter and separated.

Cinnabar (HgS) on roasting from HgO which is unstable (due to + ve ΔH°_f) at high temperature and de compose forming the metal.

Except the first one ail other reactions occur.

Furnaces are lined with refactries which are resistant to different chemicals, withstand high temperature and loads etc.

4Na₂S + 5O₂ + 2 H₂O → 2 Na₂SO₄ + 4NaOH + S

The zinc ores are sphalerite (ZnS) and ZnCO₃.

The sequence of steps should be roasting, reduction and electrolytic refining.

The uppermost part of the furnace where the temperature is 250-700°C haematite is reduced by CO whereas carbon is effective as reducing agent at high temperature.

To eliminate carbon impurities furnace is lined with heamatite.

To extract aqueous solution should not be used, only molten chemical should be used.