Metallurgy

I. Siderite $\left(\mathrm{FeCO}_3\right)$ and (III)

Calamine $\left(\mathrm{ZnCO}_3\right)$ are carbonate ions.

II. Kaolinite : $\mathrm{Al}_2 \mathrm{Si}_2 \mathrm{O}_5(\mathrm{OH})_4$

[Aluminium ore)

IV. Sphalerite : (Zn, Fe) S [sulphur ore]

Thus I and III are carbonate ore.

Monds process is used to obtain pure nickel

$ \mathrm{Ni}=(28)=[\mathrm{Ar}] 3 d^8 4 s^2 $

Unpaired electrons $=2$

Zone refining is useful for producing semiconductor grade metals of high purity. In this method, meterials are repeatedly melted and solidifying narrow zone of a substance. As molten zone more along the material, impurities tends to dissolve in molten region leaving pure solid as it solidifies.

Let's analyze each option in terms of whether it contains water of crystallization or is associated with water molecules:

1. Cryolite (Na₃AlF₆)

   → This compound does not contain water molecules. It is anhydrous (no water of crystallization).

   ✅ Not associated with water molecules.

2. Bauxite (Al₂O₃·xH₂O)

   → This is a hydrated form of alumina, i.e. it does contain water molecules.

   – Associated with water.

3. Kernite (Na₂B₄O₇·4H₂O)

   → This is hydrated sodium borate, contains crystallization water.

   – Associated with water.

4. Borax (Na₂B₄O₇·10H₂O)

   → This also contains crystal water.

   – Associated with water.

✅ Correct Answer: Option A — Cryolite

Reason: Cryolite (Na₃AlF₆) is not associated with water molecules.

Let's match each process with the metal it is primarily associated with:

1. Hall-Heroult process: This is a major industrial process for the primary production of aluminum (Al). It involves the electrolytic reduction of alumina (Al₂O₃) dissolved in molten cryolite.

   • So, (A) Hall-Heroult process matches with (III) Al.

2. Mond process: This process is used for the purification of nickel (Ni). Impure nickel is reacted with carbon monoxide to form volatile nickel tetracarbonyl [Ni(CO)₄], which is then decomposed at a higher temperature to yield pure nickel.

   • So, (B) Mond process matches with (IV) Ni.

3. van-Arkel process: This process is used for the ultra-purification of metals like titanium (Ti), zirconium (Zr), and hafnium (Hf). The metal is converted into a volatile compound (e.g., iodide) and then decomposed to yield a very pure metal.

   • So, (C) van-Arkel process matches with (I) Ti.

4. Zone refining process: This method is used for obtaining highly pure metals, especially for semiconductors, by exploiting the difference in solubility of impurities in the molten and solid states of the metal. Metals like germanium (Ge), silicon (Si), gallium (Ga), and indium (In) are purified by this method.

   • So, (D) Zone refining process matches with (II) In.

Combining these matches:

• A-III

• B-IV

• C-I

• D-II

Reaction given in option (b),

$ 2 \mathrm{PbS}+3 \mathrm{O}_2 \longrightarrow 2 \mathrm{PO}+2 \mathrm{SO}_2 $

is an example of Roasting.

When an sulphide ore is heated in presence of oxygen/air, it is called as roasting.

Statement I

In the extraction of Al by the Hall–Héroult process, pure Al₂O₃ mixed with Na₃AlF₆ lowers its melting point and increases conductivity.

✅ True.

• In the Hall–Héroult process, pure alumina ($ \mathrm{Al_2O_3} $) has a very high melting point (~2050 °C).

• It is dissolved in molten cryolite ($ \mathrm{Na_3AlF_6} $) and sometimes small quantities of $ \mathrm{CaF_2} $ are also added.

• The cryolite mixture lowers the melting point to around 950–1000 °C and increases the electrical conductivity of the electrolyte.

Hence, Statement I is correct.

Statement II

Zirconium metal is purified by zone refining method.

❌ Incorrect.

• The zone refining method is used for metals that need to be extremely pure and are less reactive, such as silicon, germanium, gallium, indium, etc.

• Zirconium (and hafnium) are purified by the van Arkel (iodide) process, not by zone refining.

• This process involves conversion of crude Zr into volatile $ \mathrm{ZrI_4} $, which then decomposes on a hot filament to yield pure zirconium metal.

Hence, Statement II is not correct.

✅ Final Answer:

Option C — Statement I is correct, but Statement II is not correct.

Aniline is used as froth stabilises in froth floatation process.

Aniline stabilise the froth, allowing desired mineral particle to bubble and be seperated from the impurity in the ore slurry.

Haematite $=\mathrm{Fe}_2 \mathrm{O}_3$

The main impurity $=\mathrm{SiO}_2(x)$

This $\mathrm{SiO}_2$ is treated with calcium oxide

$ \mathrm{SiO}_2+\mathrm{CaO} \longrightarrow \underset{\text { Calcium silicate (slag) }}{\mathrm{CaSiO}_3(y)} $

I. Hg (Mercury) - Distillation

Distillation is a refining process used for volatile metals with low boiling points. Mercury is a liquid metal at room temperature and has a relatively low boiling point (356.7 °C), making it suitable for purification by distillation to separate it from non-volatile impurities.

This match is correct.

II. Cu (Copper) - Poling

Poling is a pyrometallurgical refining process used to remove small amounts of oxygen from molten copper (blister copper). In this process, green wood logs are stirred into the molten copper. The hydrocarbons in the wood act as reducing agents, converting cuprous oxide (Cu₂O) to metallic copper.

This match is correct.

III. B (Boron) - Zone refining

Zone refining is a purification technique used for producing extremely pure metals and metalloids, especially for semiconductor applications. It works on the principle that impurities are more soluble in the molten state than in the solid state. Boron is a metalloid, and ultra-pure boron is vital for certain applications. Zone refining is indeed a method used for the purification of boron, as well as silicon and germanium.

This match is correct.

IV. Ti (Titanium) - Liquation

Liquation is a refining process suitable for metals with low melting points that can be separated from higher melting point impurities (e.g., tin, lead). Titanium, however, has a very high melting point (1668 °C). Its refining typically involves methods like the Kroll process (to produce titanium sponge) followed by electron beam melting or vacuum arc remelting for further purification. Liquation is not appropriate for titanium.

This match is incorrect.

Based on the evaluation, pairs I, II, and III are correctly matched.

The final answer is $\boxed{B}$

Kaolinite : $\mathrm{Al}_2 \mathrm{Si}_2 \mathrm{O}_5(\mathrm{OH})_4$

$x=$ Aluminium ore

Malachite : $\mathrm{Cu}_2 \mathrm{CO}_3(\mathrm{OH})_2$

$y=$ Copper ore

Alloy of copper and zinc $=$ Brass $(x$ alloy)

Alloy of copper and nickel = Cupronickel ( $Y$ alloy) used for UK silver coins.

During the extraction of iron in a blast furnace, the critical reactions occurring at temperatures between 900-1500 K are:

The reaction between carbon and carbon dioxide to produce carbon monoxide:

$ \mathrm{C} + \mathrm{CO}_2 \longrightarrow 2 \mathrm{CO} $

The reduction of iron(II) oxide by carbon monoxide:

$ \mathrm{FeO} + \mathrm{CO} \longrightarrow \mathrm{Fe} + \mathrm{CO}_2 $

These reactions are integral to the iron extraction process, as the carbon monoxide produced acts as a reducing agent, facilitating the transformation of iron ore into metallic iron.

In the extraction of certain metals, impurities are removed as slag. Specifically, this process is used in the extraction of iron (Fe) and copper (Cu).

During this process, lime (calcium carbonate, CaCO₃) is used and, upon heating, it decomposes into calcium oxide (CaO) and carbon dioxide (CO₂):

$ \mathrm{CaCO}_3 \xrightarrow{\Delta} \mathrm{CaO} + \mathrm{CO}_2 $

The calcium oxide produced reacts with the impurities in the ore, commonly known as gangue, to form slag. This slag is a combination of compounds such as calcium silicate (CaSiO₃) and calcium aluminate ($\mathrm{Ca}(\mathrm{AlO}_2)_2$).

These reactions can be represented as:

$ \begin{aligned} & \text{Flux} + \text{Gangue} \longrightarrow \text{Slag} \\ & \mathrm{CaO} + \mathrm{SiO}_2 \longrightarrow \mathrm{CaSiO}_3 \\ & \mathrm{CaO} + \mathrm{Al}_2\mathrm{O}_3 \longrightarrow \mathrm{Ca}\left(\mathrm{AlO}_2\right)_2 \end{aligned} $

Wrought iron is prepared from cast iron by oxidising impurities in a reverberatory furnance lined with haematite.

$ \mathrm{Fe}_2 \mathrm{O}_3+3 \mathrm{C} \longrightarrow \underset{\text { Wrought ion }}{2 \mathrm{Fe}}+3 \mathrm{CO} $

Lime stone $\left(\mathrm{CaCO}_3\right)$ is added as a flux, to remove sulphur, silicon and phosphorous impurities.

In the extraction of iron, the type of iron obtained from a blast furnace is pig iron. Pig iron typically contains approximately 92% iron (Fe) and a carbon content ranging from 3.5% to 4.5%.

In extraction of iron from hematite ore, hot air is blown from bottom of blast furnace so that coke is to give high temperature of 2200 K .

At upper part of furnace, at $500-800 \mathrm{~K}$, iron get reduced by CO .

$ \begin{aligned} & 3 \mathrm{Fe}_2 \mathrm{O}_3+\mathrm{CO} \longrightarrow 2 \mathrm{Fe}_3 \mathrm{O}_4+\mathrm{CO}_2 \\ & \mathrm{Fe}_3 \mathrm{O}_4+4 \mathrm{CO} \longrightarrow 3 \mathrm{Fe}+4 \mathrm{CO}_2 \\ & \mathrm{Fe}_2 \mathrm{O}_3+\mathrm{CO} \longrightarrow 2 \mathrm{FeO}+\mathrm{CO}_2 \end{aligned} $

The alloy that is made up of lithium and magnesium is used to make amount plates.

In this alloy magnesium is around 843 and lithium is around $16 \%$. It is very hard and light weight.

Let's analyze each option:

Option A:

Cuprite is a copper oxide (formula: $\text{Cu}_2\text{O}$).

Haematite is an iron oxide (formula: $\text{Fe}_2\text{O}_3$).

Both are oxide ores, so this match is correct.

Option B:

Calamine is a historical name used for zinc carbonate minerals like smithsonite (formula: $\text{ZnCO}_3$).

Siderite is an iron carbonate (formula: $\text{FeCO}_3$).

Both belong to the carbonate ore group, so this match is correct.

Option C:

Magnetite is an iron oxide (formula: $\text{Fe}_3\text{O}_4$).

The term “matachite” is questionable and “sticate ores” is not a standard classification.

Magnetite belongs to oxide ores, not a supposed “sticate” category.

Therefore, this match is incorrect.

Option D:

Sphalerite is a zinc sulphide (formula: $\text{ZnS}$).

“Fool's gold” refers to pyrite, which is an iron sulphide (formula: $\text{FeS}_2$).

Both are sulphide ores, making this match correct.

Based on the above, the incorrectly matched set is in Option C.

Answer: Option C.

The two major constituents of Portland cement are:

Option A: $\mathrm{CaO}, \mathrm{SiO}_2$

Portland cement primarily consists of lime (calcium oxide, $\mathrm{CaO}$) and silica (silicon dioxide, $\mathrm{SiO}_2$). These two components contribute to the strength and durability of the cement. While other oxides like $\mathrm{Al}_2\mathrm{O}_3$ and $\mathrm{Fe}_2\mathrm{O}_3$ are also present in Portland cement, they are not considered as major constituents compared to $\mathrm{CaO}$ and $\mathrm{SiO}_2$.

Reaction,

Hence, ZnO + HCl $\longrightarrow$ ZnCl$_2$ + H$_2$O

$\begin{aligned} & \underset{\text { Zinc chloride }}{2 \mathrm{ZnCl}_2}+2 \mathrm{~K}_4\left[\mathrm{Fe}(\mathrm{CN})_6\right] \longrightarrow \mathrm{K}_2 \mathrm{Zn}_3\left[\mathrm{Fe}(\mathrm{CN})_6\right]_2 \\ & +6 \mathrm{KCl} \end{aligned}$

$\therefore$ D is Zn(zinc) and C is Na$_2$ZnO$_2$.