Animated Solution for Chemistry - Metallurgy: Calamine, malachite, magnetite and cryolite, respectively are

The study of metallurgy is not just about memorizing chemical reactions; it is about understanding the raw materials that the Earth provides us. Before we can extract pure, shiny metals to build our modern world, we must first identify and process the rocky, impure minerals known as ores.

In this classic JEE Advanced problem, we are tested on our fundamental knowledge of four incredibly important ores: Calamine, Malachite, Magnetite, and Cryolite.

Let's embark on a journey to decode each of these minerals, understanding not just their chemical formulas, but the fascinating chemistry behind them.

You might wonder why an exam as conceptually rigorous as JEE Advanced tests your memory of mineral formulas. The truth is, inorganic chemistry is the vocabulary of the chemical sciences.

Just as you cannot write a beautiful poem without knowing words, you cannot master complex metallurgical processes—like Ellingham diagrams, roasting, calcination, and electrolytic reduction—without knowing the exact chemical nature of the starting materials.

When a question asks about the self-reduction of a copper ore, you must instantly know whether the ore is a sulfide or a carbonate. When a question discusses the magnetic separation of impurities, knowing that magnetite is ${\text{Fe}}_3{\text{O}}_4$ allows you to predict its behavior on a magnetic conveyor belt.

These formulas are not just random letters and numbers; they are the keys that unlock the physical and chemical behavior of the elements.

Calamine

When you hear the word "calamine," your mind might immediately jump to the pink lotion used to soothe skin rashes. Interestingly, there is a direct chemical connection!

In the realm of metallurgy, calamine is a historically significant ore of zinc.

Chemically, calamine is a carbonate ore, specifically zinc carbonate.

Zinc is a moderately reactive metal, and in nature, it is frequently found bound to carbonates or sulfides (like zinc blende, $\text{ZnS}$).

When extracting zinc from calamine, the first major step is calcination. By heating the ore strongly in the absence of air, the zinc carbonate decomposes to form zinc oxide and carbon dioxide gas.

This zinc oxide is then reduced using carbon to obtain pure zinc metal. Remembering that calamine is a carbonate (${\text{ZnCO}}_3$) and not a sulfate (${\text{ZnSO}}_4$) is crucial for eliminating incorrect options in multiple-choice questions.

Malachite

Next on our list is malachite, a mineral so visually striking that it has been used for thousands of years as a gemstone and a pigment.

If you have ever seen a malachite stone, you will immediately recognize its vibrant, swirling green patterns. This characteristic green color is a massive hint in chemistry—it strongly indicates the presence of copper(II) ions.

However, malachite is not just a simple copper carbonate. It is a basic copper carbonate.

This means that its crystal lattice contains both carbonate (${\text{CO}}_3^{2-}$) and hydroxide (${\text{OH}}^{-}$) anions.

Students often make the mistake of assuming malachite is just ${\text{CuCO}}_3$. The examiners know this, which is why they often include options with incomplete formulas.

Always remember the "basic" nature of this ore. The presence of the hydroxide part is what gives malachite its unique chemical stability and its specific shade of green.

Magnetite

Moving on to the third ore, we encounter magnetite. The name itself is a dead giveaway of its most famous physical property—it is naturally magnetic!

Magnetite is one of the most important and iron-rich ores found on Earth.

When studying iron extraction, you will frequently encounter two major oxide ores: haematite and magnetite. It is vital to distinguish between the two.

Haematite is iron(III) oxide (${\text{Fe}}_2{\text{O}}_3$). Magnetite, on the other hand, is a mixed oxide.

It is essentially a combination of iron(II) oxide ($\text{FeO}$) and iron(III) oxide (${\text{Fe}}_2{\text{O}}_3$). When you combine these two, you get the formula for magnetite.

A simple trick to remember this: the magnetic ore has the larger numbers in its formula (3 and 4) compared to haematite (2 and 3).

In the blast furnace, magnetite is reduced by carbon monoxide in a series of steps to eventually yield molten pig iron.

Cryolite

Finally, we arrive at cryolite, a mineral that revolutionized the aluminum industry.

Aluminum is the most abundant metal in the Earth's crust, primarily found as bauxite. Bauxite is purified to obtain alumina (${\text{Al}}_2{\text{O}}_3$).

However, extracting aluminum from alumina is incredibly difficult because alumina has a melting point of over $2000^{\circ }\text{C}$. Melting it directly would require an economically unviable amount of energy.

Enter cryolite.

Chemically, cryolite is a complex fluoride of sodium and aluminum, known as sodium hexafluoroaluminate.

In the famous Hall-Héroult process, cryolite is added to the purified alumina. This addition does two miraculous things: it lowers the melting point of the mixture to a much more manageable $900^{\circ }\text{C}$, and it significantly increases the electrical conductivity of the molten electrolyte.

Without cryolite, cheap and abundant aluminum would not exist in our modern world!

Now that we have deeply analyzed each ore, let's align our findings with the given options.

1. Calamine: ${\text{ZnCO}}_3$ 2. Malachite: ${\text{CuCO}}_3\cdot {\text{Cu(OH)}}_2$ 3. Magnetite: ${\text{Fe}}_3{\text{O}}_4$ 4. Cryolite: ${\text{Na}}_3{\text{AlF}}_6$

When we look at the choices provided in the question, we must find the exact sequence that matches our derived formulas.

Option (A) incorrectly lists zinc sulfate and simple copper carbonate. Option (C) incorrectly lists zinc sulfate and simple copper hydroxide. Option (D) correctly identifies calamine, magnetite, and cryolite, but it falls into the trap of listing malachite as a simple carbonate (${\text{CuCO}}_3$).

Only Option (B) perfectly captures the correct chemical formula for every single ore in the exact order requested.

This problem beautifully illustrates why a solid foundation in factual inorganic chemistry is essential. By understanding the unique properties and compositions of these ores, you can confidently navigate even the trickiest of multiple-choice questions!