Introduction to Metallurgy & Ores of Some Metals (Old NCERT) - Free MCQ

The mass-abundance of the nine most abundant elements in the Earth's crust is approximately: oxygen 46%, silicon 28%, aluminum 8.3%, iron 5.6%, calcium 4.2%, sodium 2.5%, magnesium 2.4%, potassium 2.0%, and titanium 0.61%.

Chalcopyrite (CuFeS2) is the ore which contains both copper and iron.

Cryolite is an important ore of aluminum that is used in the extraction of aluminum from bauxite. It is a rare mineral that occurs in small quantities in Greenland, and its chemical formula is Na3AlF6.

In chromite ore is (FeO . Cr₂O₃)
Let the oxidation state of Fe be x.
∴ x - 2 + 2 x 3 + 3 x (-2) = 0
x - 2 + 6 - 6 = 0 ⇒ x = + 2
Let the oxidation state of Cr be y
∴ 2 y + 2 - 2 + 3 x (-2 ) = 0
2 y - 6 = 0
y = 3
Hence, oxidation state of Fe and Cr are +2 and +3 respectively.

Metals having high polarising power (Z_eff) exist in ore with anions having high polarisibility
Ag, Cu, Pb →Sulphide ores (Ag₂S, CuFeS₂, Pbs)
Sn → Oxide ore (SnO₂)
Mg→Sea water and dolomite (CaCO₃, MgCO₃)
Al →Oxide ore (Al₂O₃.2H₂O)

Haematite is Fe₂O₃, in which oxidation number of iron is III. Magnetite is Fe₃O₄ which is infact a mixed oxide (FeO.Fe₂O₃), hence iron is present in both II and III oxidation state.

Statement: Zinc blende and iron pyrites are sulphides. This statement is correct because zinc blende is ZnS and iron pyrites is FeS₂.
Statement:Calamine and siderite are carbonates. This statement is correct because calamine is ZnCO₃ and siderite is FeCO₃. 
Statement: Malachite and azurite are ores of copper. This statement is also correct because malachite is Cu(OH)₂.CuCO₃ and azurite isCu(OH)₂.2CuCO₃. 
Statement: Argentite and cuprite are oxides. This statement is incorrect because argentite is Ag₂S and cuprite is Cu₂O.

A mineral is called an ore if a metal can be profiteably extracted from it. e.g. Aluminium occur in earth's crust in the form of two minerals i.e. bauxite (Al₂O₃ . 2H₂O) and clay (Al₂O₃ . 2SiO₂ . 2H₂O). Out of these two minerals aluminium can be conveniently and economically extracted from bauxite while no easy and cheap method is so far available for the extraction of aluminium from clay. Therefore, the ore of aluminium is bauxite.

Siderite is a mineral composed of iron(II) carbonate (FeCO₃)

Glauber's salt, common name for sodium sulfate decahydrate, Na₂SO₄.10H₂O. It occurs as white or colorless monoclinic crystals. Upon exposure to fairly dry air, it effloresces, forming powdery anhydrous sodium sulfate.

Sodium nitrate is the chemical compound with the formula NaNO₃. This alkali metal nitrate salt is also known as Chile saltpeter (large deposits of which were historically mined in Chile) to distinguish it from ordinary saltpeter, potassium nitrate. The mineral form is also known as nitratine, nitratite or soda niter.

Calamine (ZnCO₃), Siderite (FeCO₃), Malachite (CuCO₃ . Cu(OH)₂), Calcite (CaCO₃), Azurite (2CuCO₃ . Cu(OH)₂), Witherite (BaCO₃).  MAGNESITE IS MgCO3 and DOLOMITE is CaCO3.MgCO3.

Plaster of Paris is not a mineral. It is a building material made by heating gypsum, a mineral, to remove its water content. The other three options (Gypsum, Litharge, and Galena) are indeed minerals.

Feldspar = KAISi₃O₈, Cryolite (3NaF.AlF₃ or Na₃AlF₆).
Sylvine= KCI, Carnallite = KCI.MgCI₂ . 6H₂O

Ruby silver = Pyrargyrite(3Ag₂S.Sb₂S₃ or Ag₃SbS₃),
Horn silver = AgCI
German silver = An alloy of Cu + Zn + Ni and Quick silver = Mercury.

The correct answer is option A
The impurities associated with minerals used in metallurgy are collectively called Gangue.

Elements which are not attached by moisture, oxygen and carbon dioxide of the air occur in the native state, e.g. Au, Pt, and noble gases.

(i) → (t), (ii) → (s), (iii) → (q), (iv) → (p)

(i) → (r), (ii) → (s), (iii) → (p), (iv) → (q,t)

The carbonate ores are siderite, azurite. calamine, calcite, magnesite.

Fluorapatite is 3Ca₃(PO₄)₂ . CaF₂ or Ca₉(PO₄)6CaF₂.

The oxide ores are pyrolusite, rutile, cassiterite, haematite and cuprite.

Silicon is present in Beryl = 3 BeO .  AI₂O₃ . 6SiO₂;
Mica = K₂O . 3AI₂O₃ . 6SiO₂ . 2H₂O 
Zn₂SiO₄ = Willemite; Feldspar = KAISi₃O₈.
China clay = Al₂O₃ . 2SiO₂ . 2H₂O (or) [AI₂(OH)₄ Si₂O₅]
Silicon is not present in
Limonite = 2Fe₂O₃ . 3H₂O; Pyrargyrite (Ruby silver)
= 3Ag₂S₃Sb₂S₃.

Chromite (Fe₂CrO₄), Limonite (Fe₂O₃ . 3H₂O), Cryolite
(Na₃AIF₆), Caliche (NalO₃), Diaspora (Al₂O₃ . H₂O).

Aluminium cannot be extracted from clay profitably.