Constantan is a copper-nickel alloy usually consisting of 55% copper and 45% nickel. Hence, statement B is only false.

Tennantite (Cu₁₂As₄S₁₃) is 51.6% of copper. Hence it is the least pure.

Willemite (ZnSiO₃) is the ore of zinc.

Frary metal consists of 97% Pb, 2% Ba and 1% Ca.

Crocoisite (PbCrO₄) is the ore of lead. Felspar (KAlSi₃O₈) is the mineral of potassium and Aluminium. Cerussite (PbCO₃) is the carbonate ore of lead. Malachite (Cu(OH)₂.CuCO₃) is the carbonate ore of copper. Hence, this is the  correct representation of the codes A - 1, B - 3, C - 2, D - 4.

In the extraction of iron, in roasting step all pure haematite is converted to ferrous oxide (FeO) that combines with oxygen and form Fe₂O₃. So, the final product of the roasting step is FeO₃ in the extraction of iron, and hence  there is no need of roasting.

Galena (PbS) is the sulphide ore of Pb. Dolomite (CaCO₃.MgCO₃) is the carbonate ore of Mg. Mica (K₂O.3Al₂O₃.6SiO₂.2H₂O) is the silicate ore of Al. Zincite (ZnO) is the oxide ore of Zn. Hence, the correct answer using the codes is P - 1, Q - 4, R - 2, S - 3.

Mn and Cr metals are extracted by the reduction with Al thermite process. The reduction potentials of Mn and Cr are - 1.08 V and - 0.74 V, which favours the reduction by Al thermite process.

The chief ores of lead are - Anglesite (PbSO₄), Galena (PbS), crocoisite (PbCrO₄), Cerrusite (PbCO₃), etc.

Wood’s metal is composed of 50% Pb, 25% Sn, 12.5% Cd and 12.5% Bi. This alloy has melting point of 80^oC and used in soldering. Monel metal is composed of 68% Ni, 27% Cu and 5% Fe and used in the making of boilers of ships. Hence, statement Q is  false.

Babbit metal is composed of 90% Sn, 7% Sb and 3% Cu used in bearings of machinery. Gun metal consists of 88% Cu, 10% Sn, 2% Zn and 0.5% Pb. Frary metal is composed of 97% Pb, 2% Ba and 1% Ca. Rose metal is consist of 50% Bi, 25% Pb and 25% Sn. Hence, this is the  correct answer P - 3, Q - 1, R - 4, S - 2.

Yes, it is the correct answer. Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, deep purple, to rusty red. The oxide ore of iron are- magnetite (Fe₃O₄), hematite (Fe₂O₃). Limonite (Fe₂O₃.3H₂O) is hydrated oxide ore of iron. Siderite (FeCO₃) is the carbonate ore of iron.

Bauxite (Al₂O₃.2H₂O) is the ore of aluminium. The chemical formula for gibbsite is Al₂O₃.3H₂O.

Duralumin is composed of 94% Al, 4% Cu, and 2% Mg, Mn & Si. Electron alloy is consists of 95% Mg, 4.5% Zn and 0.5% Cu. Dutch metal contains 80% Cu and 20% Zn. Rose metal is consist of 50% Bi, 25% Pb and 25% Sn. Hence, the answer using the codes is A - 5, B - 1, C - 3, D - 2.

Galena (PbS) is the sulphide ore of lead. Willemite (ZnSiO₃) is the silicate ore of zinc. Hence, statement R is only incorrect.

Cerrosafe alloy contains 42.5% Bi, 37.7% Pb, 11.3% Sn and 8.5% Cd. Field’s metal consists of 51% In, 32.5% Bi and 16.5% Sn. Vitallium is a trademark for an alloy of 60% cobalt, 20% chromium, 5% molybdenum and 15% other substances. Nordic gold is the gold-coloured copper alloy consisting of 89% copper, 5% aluminium, 5% zinc and 1% tin. Hence, the correct answer using the codes is P - 3, Q - 1, R - 4, S - 2.

Anhydrous magnesium chloride is regenerated from magnesium hydroxide or magnesium carbonate using hydrochloric acid. In order to obtain anhydrous magnesium chloride from hydrated form by heating, hydrolysis of MgCl₂ takes place that produce MgO. Thus anhydrous MgCl₂ cannot be prepared by direct heating of hydrated MgCl₂. Hence, both A and R are true.

Bornite (2Cu₂S.CuS.FeS) and chalcopyrite (CuFeS₂) are the sulphide ores of copper. Gibbsite (Al₂O₃.3H₂O) is the hydrated oxide ore of aluminium. Anglesite (PbSO₄) is the ore of lead. Hence, S is only lead ore among the given ores.

Yes, it is the correct answer, as the statement is false. Manganin is a trademarked name for an alloy of typically 86% copper, 12% manganese and 2% nickel. Manganin foil and wire is used in the manufacture of resistors, particularly ammeter shunts, because of its virtually zero temperature coefficient of resistance value.

Hg is extracted by cyanide reduction method. K is extracted by electrolysis of fused salts, usually chlorides. Pb metal is extracted by carbon reduction method. Zn metal is extracted by the reduction with Al thermite process. Hence, the correct answer using the codes is P - 3, Q - 1, R - 4, S - 2.