Alloys — Set 2
Chemistry · मिश्र धातुएं · Questions 11–20 of 50
What is the primary alloy used to make coins in many countries?
Correct Answer: B. Cupro-nickel
Cupro-nickel is a mixture of copper and nickel that provides durability and resistance to wear. It retains its shine over long periods of circulation and is difficult to counterfeit. Nickel is a ferromagnetic metal, which can be useful for coin-operated machines.
Which of these alloys is characterized by its property of 'shape memory'?
Correct Answer: B. Nitinol
Nitinol is an alloy of Nickel and Titanium that can return to its original shape after being deformed. This unique property is activated by a change in temperature or stress. It is extensively used in medical stents and orthodontic braces.
Which alloy of copper and zinc is used for making cheap jewelry and musical instruments?
Correct Answer: C. Brass
Brass is preferred for musical instruments like trumpets because of its excellent acoustic properties and workability. Its bright gold-like appearance also makes it a popular choice for decorative jewelry. Copper, the base of brass, was the first metal used by humans.
The alloy 'Invar' is famous for having a very low coefficient of what?
Correct Answer: C. Thermal expansion
The correct answer is 'Thermal expansion'. Invar is a nickel-iron alloy that does not significantly expand or contract with temperature changes. This stability makes it perfect for precision instruments like clocks and seismic creep gauges. The name 'Invar' is derived from the word 'invariable'.
Which of the following describes an alloy?
Correct Answer: C. A homogeneous mixture
Alloys are considered homogeneous mixtures because the components are uniformly distributed at the atomic level. Unlike compounds, the ratio of elements in an alloy can be varied to achieve specific properties. Most alloys consist of a primary metal mixed with other metals or non-metals.
What is the primary constituent of 'Bell Metal'?
Correct Answer: A. Copper
Bell metal is a specific type of bronze consisting of about 80% copper and 20% tin. This high tin content creates a hard, brittle material that produces a long-lasting, resonant sound. It has been used for centuries to cast church bells and cymbals.
Which alloy is typically used for making the filaments of early incandescent bulbs?
Correct Answer: D. Tungsten-based alloys
Tungsten alloys are used because they have the highest melting point of all known metals. This allows the filament to reach extremely high temperatures and glow brightly without melting. Tungsten is represented by the symbol 'W' on the periodic table.
Which metal is added to Iron to produce 'Invar'?
Correct Answer: D. Nickel
Invar is composed of approximately 64% iron and 36% nickel. Adding nickel to iron in this specific proportion drastically reduces the rate of thermal expansion. It was discovered by Charles Édouard Guillaume, who won a Nobel Prize for it.
Which alloy is predominantly used for making surgical instruments?
Correct Answer: B. Stainless Steel
Stainless steel is chosen because it can be easily sterilized and does not rust when exposed to chemicals or body fluids. Its durability ensures that the instruments remain sharp and functional over many uses. It is also non-reactive, ensuring patient safety during procedures.
Monel metal is a highly corrosion-resistant alloy consisting of which two metals?
Correct Answer: B. Nickel and Copper
Monel is composed of roughly 67% nickel and 30% copper, along with small amounts of other elements. It is stronger than pure nickel and is especially resistant to corrosion by seawater and acids. This makes it ideal for marine engineering and chemical processing equipment.