Problem 78 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

Which of the following alloys contain(s) \(\mathrm{Cu}\) and \(\mathrm{Zn}\) ? (a) Bronze (b) Brass (c) Gun metal (d) Type metal

Step-by-Step Solution

Answer

Brass (b) contains Cu and Zn.

Step 1: Identify the composition of each alloy

Each alloy has a specific composition. Bronze is primarily composed of copper (Cu) and tin (Sn). Brass is an alloy of copper (Cu) and zinc (Zn). Gun metal is mainly composed of copper (Cu), tin (Sn), and a small amount of zinc (Zn). Type metal is typically composed of lead (Pb), antimony (Sb), and tin (Sn).

Step 2: Determine which alloys contain both Cu and Zn

From Step 1, we see that brass contains both copper (Cu) and zinc (Zn). Gun metal may also contain a small amount of zinc, but it is primarily composed of copper and tin. The rest of the alloys do not contain zinc.

Step 3: Choose the correct answer(s) from the given options

Brass contains both copper (Cu) and zinc (Zn), aligning with option (b). Gun metal can also contain zinc, but zinc is not a defining component of the alloy, so the primary answer remains option (b).

Key Concepts

Brass

Brass is a very common alloy made up of copper and zinc. It is loved for its attractive gold-like appearance and its corrosion resistance, making it ideal for decorative and functional uses.
This alloy has been used for centuries in a variety of applications, such as making musical instruments, decorative artifacts, and plumbing goods.
Brass is known for being easy to mold and process, which is why it is a favorite in manufacturing.

• Composition of Brass: Brass typically contains 60-70% copper and 30-40% zinc.
• Properties: It is both malleable and ductile, meaning it can be easily shaped and stretched without breaking.
• Uses of Brass: Common in musical instruments like trumpets and also in various mechanical applications due to its low friction.

Composition of alloys

Alloys are mixtures of two or more elements, where at least one of the elements is a metal. The process of creating alloys is known as alloying, and it helps to combine the best properties of different metals.
The specific composition of an alloy determines its distinct properties, such as strength, ductility, corrosion resistance, and appearance.

• Alloying Elements: Elements like tin, zinc, nickel, and lead are often added to metals to form various alloys.
• Purpose of Alloying: To enhance properties such as tensile strength, corrosion resistance, or to achieve a specific color.
• Examples: Steel (iron and carbon), bronze (copper and tin), and brass (copper and zinc).

Copper-Zinc alloys

Copper-zinc alloys primarily refer to brass, which is determined by varying the amount of zinc added to copper. The changes in zinc content can tweak the properties of the brass, making it suited for various applications.
While brass is the most common copper-zinc alloy, there are several variations that can include small amounts of other elements to modify their properties.

• Variations: Changing zinc ratios can result in different strengths, colors, and levels of workability.
• Trade-offs: More zinc can make the alloy stronger but less resistant to corrosion.
• Specialty Alloys: Some are used in lower friction applications, while others are preferred for their aesthetic qualities.