Problem 7 - A Complete Resource Book in Chemistry for JEE Main

Question

Misch metal is (a) an alloy of copper (b) an alloy of lanthanoid metal (c) an alloy of aluminium (d) a mixture of chromium and lead chromate

Step-by-Step Solution

Answer

Misch metal is an alloy of lanthanoid metal (Option b).

Step 1: Understand the Definition of Misch Metal

Misch metal primarily refers to an alloy composed of rare earth metals, predominantly lanthanoids. This understanding is crucial before proceeding with the identification of the correct option.

Step 2: Analyze the Given Options

Read through the options to relate them to the composition of the mixture known as Misch metal. The options are: - (a) An alloy of copper - (b) An alloy of lanthanoid metal - (c) An alloy of aluminium - (d) A mixture of chromium and lead chromate.

Step 3: Match Misch Metal to Lanthanoids

Since Misch metal mostly consists of lanthanoids such as cerium, lanthanum, and neodymium, option (b) correctly identifies Misch metal as an alloy of lanthanoid metal.

Step 4: Eliminate Incorrect Options

Verify that the other options do not correspond to the known composition of Misch metal: - Option (a): Copper alloys are different categories of metals like bronze and brass. - Option (c): Aluminium alloys include different elements like copper for aerospace. - Option (d): Chromium mixed with lead chromate is unrelated to Misch metal, as it focuses on lanthanoids.

Key Concepts

Lanthanoid Metals

Lanthanoid metals are a group of elements in the periodic table, often referred to as rare earth elements. They include 15 metallic elements with atomic numbers from 57 to 71, ranging from lanthanum to lutetium. These metals are known for their similar properties and are often found together in minerals. Lanthanoids are typically shiny and silvery-white. They may tarnish when exposed to air and are known to have high melting and boiling points. These metals are significant for their magnetic and phosphorescent properties, making them vital to various technological applications.

Alloys

An alloy is a combination of metals or a metal and another element. Alloys are created to enhance the properties of individual metals, such as strength, durability, or resistance to corrosion. For instance, steel is an alloy of iron with carbon, greatly increasing iron's strength and endurance. The unique property of alloys is that their characteristics differ from those of their component elements, offering specialized benefits for different industrial purposes. For example, Misch metal is an alloy primarily of lanthanoid metals, used in lighter flints and other applications where ignition is essential. Creating alloys allows engineers and chemists to tailor materials to specific needs.

Rare Earth Metals

Rare earth metals are a group of 17 elements within the periodic table, including the lanthanoids plus scandium and yttrium. Despite their name, these elements are relatively abundant in the Earth's crust, but they tend to be dispersed, making them challenging to extract in pure form. These metals play a crucial role in modern technology. For example, they are used in smartphones, electric vehicles, wind turbines, as well as in numerous other electronic devices and advanced applications due to their unique optical and magnetic properties. Their importance in high-tech industries highlights the need for efficient and sustainable mining practices.

Cerium

Cerium (Ce) is the most abundant of the rare earth elements and makes up a significant portion of Misch metal. This element is commonly used in self-cleaning ovens, gas mantles, and as a catalyst in the automotive industry. Cerium's ability to release and absorb oxygen easily allows it to play a vital role in catalytic converters, reducing vehicle emissions. Additionally, cerium oxide is widely used in glass polishing agents and protective coatings. Its versatile applications make cerium a crucial component in both industrial and consumer products.

Lanthanum

Lanthanum (La), another key component of Misch metal, is a soft and ductile metal that is often used in camera lenses and arc lighting. This element is essential in the production of night vision goggles and in the steel industry to improve the mechanical properties of steel. Lanthanum is also used in hydrogen storage and rechargeable batteries, particularly nickel-metal hydride batteries found in hybrid vehicles. Its remarkable conductivity and ability to form stable compounds bring significant benefits to modern technology and industry.

Neodymium

Neodymium (Nd) is a vital component in the formulation of strong permanent magnets, known as neodymium magnets, undoubtedly the most powerful commercially available magnets. These magnets are found in various high-performance electric motors and generators, such as those found in electric and hybrid vehicles. Neodymium is also used in lasers, headphones, computer hard disks, and microphones due to its high magnetic strength. Its indispensable role in producing lightweight, portable gadgets and reducing carbon emissions showcases neodymium's substantial influence on modern industrial and technological advancements.