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Alloys and Their Uses – NDA Chemistry PYQs
Coastal States, Gulfs, Straits, Islands and Maritime Zones of India
Indian Geography • Coastal Geography • PYQs Included
Q1. Bronze is often used to make statues and medals whereas brass is used in making utensils, scientific apparatus and cartridges. Both are copper-containing alloys, yet they differ in additionally containing:
(a) Zinc in brass and tin in bronze
(b) Chromium in brass and nickel in bronze
(c) Nickel in brass and tin in bronze
(d) Iron in brass and nickel in bronze
Answer: (a) Zinc in brass and tin in bronze
Brass = Cu + Zn. Bronze = Cu + Sn. Both contain copper — brass has zinc as the additional metal, bronze has tin. This is the single most tested alloy fact across NDA and CDS.
[NDA 2011-I]
Q2. Solder is an alloy of:
(a) Cu and Sn (b) Fe and Zn (c) Pb and Sn (d) Ag and Zn
Answer: (c) Pb and Sn
Solder is Lead + Tin. Its low melting point (~183°C) lets it melt and flow into electrical joints without damaging surrounding components. Cu + Sn = bronze. Fe + Zn = not a standard alloy.
[NDA 2021-I]
Q3. Bronze is an alloy of:
(a) Cu and Zn (b) Cu and Sn (c) Zn and Mg (d) Fe and Cu
Answer: (b) Cu and Sn
Bronze = Copper + Tin. Cu + Zn = Brass. This confusion is tested repeatedly.
[NDA 2022-II]
Q4. Which one of the following is NOT a solution?
(a) Alloy (b) Milk (c) Air (d) Sugar
Answer: (d) Sugar
Alloy, milk, and air are all homogeneous mixtures. Sugar is a pure compound — not a mixture.
[NDA 2022-I]
Q5. German silver is an alloy of:
(a) Gold and silver (b) Copper and silver
(c) Copper, zinc and silver (d) Copper, zinc and nickel
Answer: (d) Copper, zinc and nickel
German Silver contains NO actual silver. It is Cu + Zn + Ni — named only for its silver-like appearance. Option (c) is the designed trap.
[NDA tested via CDS]
Q6. Match the alloy with its composition:
A. Solder — B. Brass — C. Bronze — D. Steel
- Fe + C — 2. Cu + Zn — 3. Cu + Sn — 4. Pb + Sn
Answer: A-4, B-2, C-3, D-1
Solder = Pb + Sn (4) | Brass = Cu + Zn (2) | Bronze = Cu + Sn (3) | Steel = Fe + C (1).
[NDA tested via CDS]
Q7. The heating coil in an electric heater is made of:
(a) Nichrome (b) Tungsten (c) Copper (d) Iron
Answer: (a) Nichrome
Nichrome (Ni + Cr) has very high electrical resistance and does not oxidise at high temperatures. Copper has very low resistance — it carries current without generating much heat. High resistance = efficient heat generation.
[NDA tested via CDS]
Q8. Which one of the following is the correct way to store curd?
(a) Copper vessel (b) Stainless steel vessel (c) Bronze vessel (d) Brass vessel
Answer: (b) Stainless steel vessel
Curd is acidic. Acids react with copper (and copper alloys like bronze and brass) — producing toxic copper compounds. Stainless steel is chemically inert and safe for acidic foods.
[NDA 2023-I]