Problem 2 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Mischmetal is an alloy consisting mainly of: (a) lanthanoid metals (b) actinoid and transition metals (c) lanthanoid and actinoid metals (d) actinoid metals

Step-by-Step Solution

Answer

(a) lanthanoid metals

Step 1: Understanding Mischmetal

Mischmetal is an alloy typically used in the manufacturing of flints for lighters. It is primarily composed of a mixture of rare-earth elements.

Step 2: Composition of Mischmetal

The main components of mischmetal are lanthanoid metals. These are elements from the lanthanide series, which include cerium, lanthanum, and neodymium among others.

Step 3: Identifying the Correct Answer

Given its composition, mischmetal consists mainly of lanthanoid metals. There is no significant incorporation of actinoid metals or transition metals in its typical composition.

Step 4: Selecting the Correct Option

Based on the composition described, the correct option among the given choices is (a) lanthanoid metals.

Key Concepts

Lanthanoid Metals

Lanthanoid metals, often referred to as lanthanides, are a group of 15 chemical elements with atomic numbers from 57 to 71. These elements are located in the f-block of the periodic table, situated between the actinoids and the transition metals.
Lanthanides are known for their similar chemical properties, which result from having similar electron configurations. This similarity makes them challenging to separate from each other through chemical processes. Important members of this group include:

• Cerium (Ce): With an atomic number of 58, cerium is the most abundant of the lanthanides.
• Lanthanum (La): Known for its role in various industrial applications.
• Neodymium (Nd): Widely used in powerful magnets and in the production of lighter flints.

These metals are essential to high-tech industries because of their special properties like magnetic, luminescent, and catalytic capabilities.

Lighter Flint Manufacturing

The manufacturing of lighter flints involves the use of an alloy known as mischmetal, which is primarily composed of rare-earth elements. The flints in lighters are small yet crucial components that create sparks when struck against a rough surface.

The ability of mischmetal to produce sparks is largely due to its composition of lanthanoid metals like cerium and lanthanum, combined with small amounts of iron and magnesium. When the flint is struck, cerium oxidizes quickly, generating enough heat to produce a spark. This spark then ignites the fuel in the lighter, causing a flame.

• Durability: The alloy must withstand repeated use and maintain its spark-producing capability.
• Consistency: Consistent production quality ensures that each flint delivers a reliable performance.

Overall, the design and composition of lighter flint are crucial for the efficient functioning of lighters, making the choice of materials particularly important.

Rare-Earth Elements

Rare-earth elements are a set of 17 chemical elements within the periodic table that are crucial for many of today’s technologies. They are often divided into the lanthanides, plus scandium and yttrium, due to their similar properties.
Despite their name, these elements are relatively abundant in the Earth's crust but challenging to extract economically due to their dispersion and complex ore formations.

• Applications: Technologies such as smartphones, electric vehicles, wind turbines, and many others depend heavily on rare-earth elements.
• Properties: Their unique magnetic, luminescent, and electrochemical properties make them integral to modern innovations.
• Extraction Challenges: Isolation and purification require intricate and often environmentally-impactful processes.

Understanding the importance of rare-earth elements is key to advancing and maintaining many technological solutions in our daily lives. They provide benefits that are essential for modern conveniences and technological advancement.