Animated Solution for Chemistry - General Principles and Processes of Isolation of Metals: The ore that contains both iron and copper is

The journey of extracting metals from the Earth's crust begins with a fundamental understanding of minerals and ores. In the fascinating world of metallurgy, knowing the chemical composition of various ores is not just a matter of rote memorization; it is the absolute key to unlocking the entire extraction process. Every metal has a unique story of how it is bound to other elements in nature, and deciphering these chemical bonds is the first step for any metallurgist.

In this particular problem, we are presented with a unique and specific challenge. We need to identify an ore that serves as a dual repository, containing both iron ($\text{Fe}$) and copper ($\text{Cu}$). To solve this, we must embark on a systematic investigation of the four options provided: malachite, azurite, dolomite, and copper pyrites. Let us dissect each of these minerals to uncover their elemental secrets and understand their role in the broader context of inorganic chemistry.

Malachite

Our first candidate in this investigation is malachite. If you have ever marveled at antique green statues, ornamental boxes, or vibrant green jewelry, you have likely seen malachite in all its glory. It has been mined since antiquity and holds a special place in human history.

Chemically, malachite is classified as a basic copper carbonate. Its chemical formula is written as $CuC{O}_3\cdot Cu(OH{)}_2$. When we break down this formula, we can clearly identify the presence of copper ($\text{Cu}$), carbon ($\text{C}$), oxygen ($\text{O}$), and hydrogen ($\text{H}$). The presence of the hydroxide ion ($O{H}^{-}$) is what makes it "basic."

While malachite is an excellent and historically significant ore of copper, a careful inspection of its formula reveals a complete absence of iron. It is a pure copper mineral in terms of its heavy metal content. Therefore, despite its immense importance in early copper metallurgy and its striking visual appeal, malachite does not satisfy our strict requirement of containing both iron and copper. We must look elsewhere.

Azurite

Moving on to the second option, we encounter azurite. Azurite is very closely related to malachite and is often found alongside it in nature, forming beautiful green and blue banded patterns in rocks. It is renowned for its deep, mesmerizing blue color, which has been crushed and used as a vibrant pigment by artists for centuries, particularly during the Renaissance.

Like malachite, azurite is also a basic carbonate of copper. However, its chemical formula is slightly different, reflecting a different ratio of carbonate to hydroxide. It is represented as $C{u}_3(C{O}_3{)}_2(OH{)}_2$, which is sometimes written as $2CuC{O}_3\cdot Cu(OH{)}_2$ to show its relation to malachite.

Once again, scanning this formula reveals a rich concentration of copper atoms. It is undeniably a fantastic source of copper. But just like our previous candidate, azurite is entirely devoid of iron. The chemical lattice simply does not accommodate iron atoms. Thus, we must eliminate azurite from our list of potential answers.

Dolomite

Our third suspect is dolomite. Unlike the first two options, dolomite is not an ore of a transition metal. Instead, it is a very common rock-forming mineral that makes up significant portions of the Earth's crust, particularly in massive sedimentary rock formations known as dolostones.

Dolomite is a double carbonate of two alkaline earth metals: calcium and magnesium. Its precise chemical formula is $CaMg(C{O}_3{)}_2$. It forms when magnesium-rich groundwater replaces some of the calcium in standard limestone ($CaC{O}_3$).

A quick elemental check of the formula shows the presence of calcium ($\text{Ca}$) and magnesium ($\text{Mg}$), along with the carbonate group. There is absolutely no trace of either copper or iron in pure dolomite. While it is incredibly useful in the construction industry and as a source of magnesium, it is completely irrelevant to our search for a copper-iron ore. Consequently, we can confidently discard this option.

Copper Pyrites

Finally, we arrive at our last option: copper pyrites. This mineral is scientifically known as chalcopyrite, and it is the undisputed king of copper ores.

Here lies a classic metallurgical trap that examiners love to set! The common name "copper pyrites" prominently features the word "copper," which might lead an unwary student to assume it is a pure copper compound, perhaps a simple copper sulfide. However, the term "pyrites" in mineralogy generally refers to sulfide minerals that often contain iron. The most famous example is iron pyrite ($Fe{S}_2$), which is universally known as "fool's gold" due to its deceptive metallic luster.

Let us look at the exact chemical formula of copper pyrites: $CuFe{S}_2$.

Aha! The formula reveals the truth. Along with copper ($\text{Cu}$) and sulfur ($\text{S}$), we clearly see the symbol $\text{Fe}$, which stands for iron. Copper pyrites is a mixed sulfide ore that naturally contains both copper and iron in its crystal lattice. This perfectly matches the criteria set by our question!

The fact that copper pyrites contains both iron and copper is not just a random trivia fact; it has profound and complex implications for the industrial extraction of copper. Copper pyrites is, in fact, the most abundant and principal ore of copper worldwide, accounting for the vast majority of global copper production.

Because the ore contains a significant amount of iron—essentially a 1:1 atomic ratio with copper—the metallurgical process to extract pure copper becomes quite an intricate dance of chemistry. You cannot simply melt it down and get copper; you have to actively fight to remove the iron.

During the extraction process, the concentrated copper pyrites ore is first roasted in the presence of excess air. This converts the sulfides into oxides: Further roasting converts the iron sulfide into iron oxide:

Now, the metallurgist faces a problem: how to get rid of this $FeO$? This is where the concept of a flux comes in. During the smelting phase in a reverberatory furnace, silica ($Si{O}_2$) is added to the mixture. Silica acts as an acidic flux and reacts specifically with the basic iron oxide ($FeO$) to produce iron silicate ($FeSi{O}_3$), which is a molten slag.

This iron silicate slag is lighter than the molten mixture of copper and iron sulfides (known as copper matte) and floats on top of it. It can then be easily skimmed off, effectively separating the iron from the copper. This elegant chemical trick is the only reason we can economically extract copper from an ore that is half iron!

Through our systematic analysis of the chemical formulas, we have deduced that out of the given choices, copper pyrites ($CuFe{S}_2$) is the only ore that houses both iron and copper.

This problem beautifully highlights the critical importance of memorizing the chemical formulas of common ores for competitive exams like JEE and NEET. It is not merely about knowing the names to score marks, but understanding the exact elemental composition that dictates how these metals behave, how they bond, and ultimately, how they are isolated and purified in the massive industrial furnaces of the real world.