Problem 141 - A Complete Resource Book in Chemistry for JEE Main

Question

Match the following: List-I List-II 1\. Bell metal (i) \(\mathrm{Cu}: 60 \%-80 \%, \mathrm{Zn}: 20 \%-40 \%\) 2\. Gun metal (ii) Cu: \(75 \%-90 \%\), Sn: \(10 \%-25 \%\) 3\. Bronze (iii) \(\mathrm{Cu}: 88 \%, \mathrm{Sn}: 10 \%, \mathrm{Zn}: 2 \%\) 4\. Brass (iv) Cu: \(80 \%\) Sn: \(20 \%\) The correct matching is: \(\begin{array}{llll}1 & 2 & 3 & 4\end{array}\) (a) (iv) (iii) (ii) (i) (b) (iii) (iv) (ii) (i) (c) (iv) (ii) (i) (iii) (d) (iii) (iv) (i) (ii)

Step-by-Step Solution

Answer

The correct matching is (b): 1-(iv), 2-(iii), 3-(ii), 4-(i).

Step 1: Identify Properties

First, understand the properties of each material mentioned in the List-I (Bell metal, Gun metal, Bronze, Brass). Bell metal typically contains copper (Cu) and tin (Sn). Gun metal usually consists of copper, tin, and sometimes zinc (Zn). Bronze is a mixture of copper and tin, and brass comprises copper and zinc.

Step 2: Analyze List-II Compositions

Next, analyze the compositions provided in List-II: (i) Cu: 60%-80%, Zn: 20%-40% (ii) Cu: 75%-90%, Sn: 10%-25% (iii) Cu: 88%, Sn: 10%, Zn: 2% (iv) Cu: 80%, Sn: 20%. Notice the percentages of Cu, Zn, and Sn given in each option.

Step 3: Match Bell Metal

Bell metal (1) typically contains a high percentage of tin (Sn). Option (iv) Cu: 80%, Sn: 20% matches this description almost exactly.

Step 4: Match Gun Metal

Gun metal (2) usually contains Cu, Sn, and sometimes a smaller amount of zinc (Zn). Option (iii) Cu: 88%, Sn: 10%, Zn: 2% has the right kind of composition for gun metal.

Step 5: Match Bronze

Bronze (3) is an alloy of copper (Cu) and tin (Sn). Option (ii) Cu: 75%-90%, Sn: 10%-25% fits this description well, as it contains only copper and tin.

Step 6: Match Brass

Finally, brass (4) is composed of copper (Cu) and zinc (Zn). Option (i) Cu: 60%-80% and Zn: 20%-40% matches this definition of brass.

Key Concepts

Bell Metal Composition

Bell metal is a fascinating alloy primarily composed of copper (Cu) and tin (Sn). It typically contains around 80% copper and 20% tin. This specific composition gives bell metal its distinguished acoustic properties, making it ideal for crafting bells. The high tin content, compared to other alloys, contributes to a distinct and resonant sound, which is why this metal has been historically favored for musical instruments and church bells.

• Copper: 80%
• Tin: 20%

In the context of alloy distinction, it's crucial to note that bell metal's composition can vary slightly, but it generally remains very close to this approximate ratio.

Gun Metal Properties

Gun metal is a strong and durable alloy usually composed of copper, tin, and a small amount of zinc (sometimes not included). Typically, the blend forms into a composition of roughly 88% copper, with 10% tin, and a pinch of zinc making up around 2%.

• Copper: 88%
• Tin: 10%
• Zinc: 2%

Originally, gun metal was used extensively for making cannons, hence its name. In modern times, gun metal is appreciated for being resistant to corrosive influences, immune to steam, and having great machinability, making it useful for valves, gears, and statues.

Bronze Alloy

Bronze is an ancient alloy that has been pivotal throughout history, consisting mainly of copper and tin. The composition of bronze makes it tough and can range significantly, from 75% to 90% copper and 10% to 25% tin, depending on its intended use.

• Copper: 75%-90%
• Tin: 10%-25%

Its durability and resistance to corrosion have historically made it a choice material for weapons, tools, and sculptures. Bronze is known for its beautiful patina, which is highly valued in art and architecture, giving creations a unique and attractive aging appearance.

Brass Composition

Brass is a vibrant and versatile metal alloy formed from copper and zinc. Its typical composition ranges from 60% to 80% copper and 20% to 40% zinc.

• Copper: 60%-80%
• Zinc: 20%-40%

The varying proportions of zinc allow brass to have numerous variations, from softer malleable forms to harder, stronger ones. Brass is renowned for its bright gold-like appearance, making it popular for decorative purposes, including musical instruments, fittings, and architectural trim. Its excellence in conductivity and machinability also makes it highly suitable for nuts, bolts, and screws.