Animated Solution for Chemistry - Metallurgy: Match List-I and List-II. $\begin{array}{ll}\text{List-I}& \text{List-II}\\ \text{A. Haematite}& \text{1. }{\mathrm{Al}}_2{\mathrm{O}}_3\cdot x{\mathrm{H}}_2\mathrm{O}\\ \text{B. Bauxite}& \text{2. }{\mathrm{Fe}}_2{\mathrm{O}}_3\\ \text{C. Magnetite}& \text{3. }{\mathrm{CuCO}}_3\cdot {\mathrm{Cu}(\mathrm{OH})}_2\\ \text{D. Malachite}& \text{4. }{\mathrm{Fe}}_3{\mathrm{O}}_4\end{array}$ Choose the correct answer from the options given below.

The study of metallurgy is incomplete without a solid grasp of the various ores from which we extract essential metals. This problem is a classic example of a memory-based question that frequently appears in JEE. It tests your direct knowledge of the chemical formulas of common ores. Let's break down each ore mentioned in the problem and understand its composition.

Iron is one of the most abundant and widely used metals on Earth, and it is primarily extracted from its oxide ores. The problem presents us with two very famous iron ores: Haematite and Magnetite.

Imagine the reddish, rust-like appearance of Haematite. It is a very common oxide ore of iron, and its chemical formula is simply ${\mathrm{Fe}}_2{\mathrm{O}}_3$. Because of its high iron content and relative abundance, it is a primary source of iron in the metallurgical industry. Therefore, Haematite (A) perfectly matches with formula (2).

Now, let's look at Magnetite. As its name beautifully suggests, this ore possesses natural magnetic properties! It is also an oxide of iron, but it has a slightly different composition. Its formula is ${\mathrm{Fe}}_3{\mathrm{O}}_4$. A great way to remember the difference is that Magnetite has more iron and oxygen atoms compared to Haematite. Thus, Magnetite (C) matches with formula (4).

Next up is Bauxite, the undisputed king of aluminium ores! Aluminium is a highly reactive metal, and in nature, it is most commonly found in the form of hydrated oxides. Bauxite is essentially a mixture of these hydrated aluminium oxides.

Its general chemical formula is written as ${\mathrm{Al}}_2{\mathrm{O}}_3\cdot x{\mathrm{H}}_2\mathrm{O}$, where '$x$' represents the variable number of water molecules attached to the alumina. This makes Bauxite (B) a direct match for formula (1).

Finally, we have Malachite. If you have ever seen ancient copper artifacts or statues turning a beautiful shade of green over time, you have witnessed the formation of compounds similar to Malachite. It is a naturally occurring green-colored ore of copper.

Chemically, it is a basic copper carbonate. The term "basic" implies the presence of hydroxide ions alongside the carbonate ions. Its exact formula is ${\mathrm{CuCO}}_3\cdot {\mathrm{Cu}(\mathrm{OH})}_2$. This means Malachite (D) matches perfectly with formula (3).

Let's bring all our findings together to find the correct option: - A (Haematite) matches with 2 (${\mathrm{Fe}}_2{\mathrm{O}}_3$) - B (Bauxite) matches with 1 (${\mathrm{Al}}_2{\mathrm{O}}_3\cdot x{\mathrm{H}}_2\mathrm{O}$) - C (Magnetite) matches with 4 (${\mathrm{Fe}}_3{\mathrm{O}}_4$) - D (Malachite) matches with 3 (${\mathrm{CuCO}}_3\cdot {\mathrm{Cu}(\mathrm{OH})}_2$)

Looking at the given options, the sequence A $\to$ 2, B $\to$ 1, C $\to$ 4, D $\to$ 3 corresponds exactly to option (d).

Questions like these are absolute lifesavers in competitive exams. They require no complex calculations and can be solved in seconds if your memory is sharp. Make sure to thoroughly revise the formulas of other important ores like Siderite (${\mathrm{FeCO}}_3$) and Copper Pyrites (${\mathrm{CuFeS}}_2$) to secure these easy marks!