Problem 122 - A Complete Resource Book in Chemistry for JEE Main

Question

Among the following statements, the incorrect one is (a) calamine and siderite and carbonates (b) argentite and cuprite are oxides (c) zinc blende and pyrites are sulphides (d) malachite and azurite are ores of copper

Step-by-Step Solution

Answer

Statement (b) is incorrect.

Step 1: Analyze Each Statement

We need to analyze each statement in the question and determine the validity of the claims about the types of mineral ores or compounds. Let's examine each option provided.

Step 2: Verify Statement (a)

Statement (a) says calamine and siderite are carbonates. Calamine is a zinc mineral, specifically a form of zinc carbonate (1ZnCO_{3}2), and siderite is iron carbonate (bFeCO_{3}d). Both are correctly classified as carbonates.

Step 3: Verify Statement (b)

Statement (b) implies argentite and cuprite are oxides. Argentite is actually a silver sulfide mineral (bAg_{2}Sd), not an oxide. Cuprite, on the other hand, is a copper oxide (bCu_{2}Od). Therefore, this statement is incorrect because argentite is not an oxide.

Step 4: Verify Statement (c)

Statement (c) states zinc blende and pyrites are sulphides. Zinc blende, also known as sphalerite, is a sulfide (bZnSd) mineral. Pyrite (bFeS_{2}d) is also a sulfide mineral. Thus, this statement is correct.

Step 5: Verify Statement (d)

Statement (d) notes that malachite and azurite are ores of copper. Malachite (bCu_{2}(OH)_{2}CO_{3}d) and azurite (bCu_{3}(OH)_{2}(CO_{3})_{2}d) are both copper carbonate minerals used as copper ores, confirming the statement is correct.

Step 6: Conclusion

From the analysis, we found that statement (b) is incorrect. Argentite is not an oxide as claimed; it should be classified as a sulfide.

Key Concepts

Carbonate Minerals

Carbonate minerals are an important group of minerals that contain the carbonate ion \(CO_3^{2-}\). These minerals form in a diverse range of environments, such as in sedimentary rocks and hydrothermal veins. The structure of carbonate minerals is characterized by a triangular arrangement in the carbonate ion, where one carbon atom is bonded to three oxygen atoms. This unique geometry leads to the variety and stability of these minerals.

• Calamine: Often referred to in mineralogy as smithsonite, calamine is primarily zinc carbonate (\(ZnCO_3\)). It's a significant ore of zinc, commonly found in oxidized zinc ores.
• Siderite: Known as iron carbonate (\(FeCO_3\)), siderite is another typical carbonate mineral, forming as part of sedimentary rock formations.
• Malachite and Azurite: These are copper carbonate hydroxide minerals with vibrant green and blue hues, used both as ores and for decorative purposes in jewelry.

With their distinctive crystal structures and vibrant colors, carbonate minerals are appreciated not only for their economic value but also for their aesthetic appeal. Understanding their formation and classification is crucial in mineral exploration and industrial applications.

Oxide Minerals

Oxide minerals are a class of minerals containing oxygen bonded to one or more metal ions. These minerals are significant for their role as ores for various metals.

• Cuprite: This is a copper oxide mineral with the formula \(Cu_2O\). It is a minor ore of copper but famous for its deep red coloration and is often used as a gemstone.
• Magnetite and Hematite: These are well-known iron oxide minerals, crucial for iron production both historically and in modern industry.

Oxide minerals, due to their simple chemical compositions and strong metal-oxygen bonds, tend to be very stable. This stability makes them resistant to weathering, which is one reason why they are often abundant at or near the Earth's surface. Their study and identification are vital in mining and geological exploration.

Sulfide Minerals

Sulfide minerals consist of one or more metals combined with sulfur. These minerals form in a wide variety of geological settings, including hydrothermal vents and sedimentary layers.

• Argentite: This is a silver sulfide mineral, \(Ag_2S\), often found in silver-bearing ore veins. Despite the incorrect classification in the exercise, argentite is not an oxide.
• Zinc Blende: Also known as sphalerite, zinc blende is \(ZnS\), the most important ore of zinc, characterized by its high zinc content.
• Pyrite: Commonly known as "fool's gold," pyrite is iron sulfide (\(FeS_2\)) and is recognized by its metallic luster and pale brass-yellow hue.

Sulfide minerals are critical to the extraction of many valuable metals. Their identification and processing are fundamental in the mining industry. They often give clues about the geothermal conditions under which they formed.

Copper Ores

Copper ores are valuable sources of copper, one of the most widely used metals in the world. Copper is essential for electrical wiring, plumbing, and many other industries due to its high conductivity and durability.

• Malachite and Azurite: These are two important copper carbonate ores. Malachite \(Cu_2(OH)_2CO_3\) and azurite \(Cu_3(OH)_2(CO_3)_2\) are prized for their striking green and deep blue colors, respectively.
• Bornite and Chalcopyrite: These are sulfide ores containing copper. Bornite (\(Cu_5FeS_4\)) and chalcopyrite (\(CuFeS_2\)) are other significant copper ores mined globally.

The extraction of copper from these ores involves several steps, including mining, concentrating, smelting, and refining. Understanding copper ores’ types and their distribution helps in optimizing the extraction process. Moreover, knowledge of copper ores plays a crucial role in ecological sustainability and economic viability in mining practices.