Problem 54 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following metal is found in gun metal, monel metal and constantan alloys? (a) \(\mathrm{Cu}\) (b) \(\mathrm{Fe}\) (c) \(\mathrm{Hg}\) (d) \(\mathrm{Zn}\)

Step-by-Step Solution

Answer

Copper (Cu) is found in gun metal, Monel metal, and Constantan alloys.

Step 1: Understand the Alloys

Gun metal, Monel metal, and Constantan are metal alloys that have specific compositions. It is important to identify which metals are used in these alloys to answer the question.

Step 2: Analyze Gun Metal Composition

Gun metal is primarily composed of copper, tin, and zinc. Therefore, copper (Cu) is included in this alloy.

Step 3: Analyze Monel Metal Composition

Monel metal mainly consists of nickel and copper. Thus, copper (Cu) is part of Monel metal.

Step 4: Analyze Constantan Composition

Constantan is an alloy of copper and nickel, typically with 55% copper and 45% nickel. Hence, copper (Cu) is in Constantan.

Step 5: Identify the Common Metal

After analyzing each alloy, copper (Cu) is the only metal found in all three: gun metal, Monel metal, and Constantan.

Key Concepts

Gun Metal

Gun metal is an ancient alloy with a fascinating history, primarily used in the casting of gun barrels. Its composition generally includes:

• Copper (Cu), accounting for about 85%
• Tin (Sn), usually around 5-15%
• Zinc (Zn), in small amounts, typically around 5%

Gun metal is renowned for its corrosion resistance and tensile strength, making it ideal for applications requiring durability and reliability. Over time, manufacturers discovered that substituting or adding different proportions could yield specific characteristics necessary for varying applications. Historical uses, such as in cannons, have primarily been replaced with more modern needs, including gears, statues, and bearings, showcasing the alloy’s continued relevance.

Monel Metal

Monel metal represents a group of nickel-copper alloys that offer extremely high resistance to corrosion. The typical composition includes:

• Nickel (Ni), around 63%
• Copper (Cu), about 28-34%
• Small amounts of iron (Fe), manganese (Mn), and other trace elements

Monel's unique properties allow it to excel in marine engineering and chemical processing equipment. It's ideal for environments exposed to sea water and other corrosive elements. The alloy's strength and durability make it optimal for use in industries where mechanical stress and corrosion resistance are key. Its application extends to oil rigs, heat exchangers, and even musical instruments, demonstrating its versatility and reliability.

Constantan

Constantan is a copper-nickel alloy known for its consistent electrical resistance over a wide temperature range. Typically, its composition is:

• Copper (Cu), approximately 55%
• Nickel (Ni), around 45%

This alloy is specially tailored for applications necessitating precise temperature measurement since its conductivity remains stable despite ambient temperature shifts. Common uses include thermocouples and resistance wire. The predictability of its behavior under changing temperatures ensures it remains a staple in industries such as aerospace and meteorology, providing unparalleled accuracy in temperature-sensitive measurements. It is this stability that gives Constantan its name and makes it indispensable in various technological applications.