Constantan is a copper-nickel alloy, typically consisting of 55% copper and 45% nickel. It is widely used in electrical engineering for its constant electrical resistance over a wide range of temperatures.
52
Which of the following minerals serves as the primary ore for the extraction of aluminium metal?
Bauxite is the principal ore of aluminium. It is a sedimentary rock with a high aluminium content, primarily consisting of aluminium minerals like gibbsite, boehmite, and diaspore, mixed with iron oxides and silica. It is processed via the Bayer process to produce alumina, which is then reduced to aluminium metal.
53
What is the typical elemental composition of the alloy known as nichrome?
Nichrome is a non-magnetic alloy primarily composed of nickel and chromium. It often contains small amounts of iron, manganese, and other elements to improve its mechanical properties and resistance to oxidation at high temperatures. It is widely used in heating elements for appliances like toasters and hair dryers due to its high electrical resistivity and heat resistance.
54
Among the listed metals, which one exhibits the highest degree of malleability?
Malleability is the ability of a metal to be hammered or rolled into thin sheets. Silver (Ag) is exceptionally malleable, surpassed only by gold among common metals. Compared to sodium, aluminum, and zinc, silver can be beaten into extremely thin leaves, making it highly valued for its physical properties.
55
What is the oxidation state (valency) of copper in cuprous oxide (Cu2O)?
In cuprous oxide (Cu2O), oxygen typically exhibits an oxidation state of -2. To maintain electrical neutrality for the molecule, the two copper atoms must collectively provide a +2 charge. Therefore, each copper atom has an oxidation state of +1. This is characteristic of the cuprous ion (Cu+), distinguishing it from the cupric ion (Cu2+).
Mercury is historically and commonly referred to as 'quicksilver' because it is a liquid metal at room temperature with a silvery, reflective appearance. The term 'quick' historically meant 'living' or 'moving', referring to its fluid, mobile nature. It is the only metallic element that is liquid under standard conditions of temperature and pressure.
57
The phenomenon of variable valency is a characteristic property of which group of elements?
Transition elements (d-block elements) are characterized by their ability to exhibit variable valency. This occurs because the energy difference between their (n-1)d and ns orbitals is small, allowing electrons from both subshells to participate in chemical bonding. This flexibility allows these elements to form ions with different charges, such as Fe2+ and Fe3+.
58
Which metal compound is primarily utilized in traditional black and white photography?
Silver halides, such as silver bromide (AgBr), are light-sensitive compounds used in photographic film. When exposed to light, silver ions are reduced to metallic silver, which creates the latent image on the film during the development process.
59
What is the chemical reaction between hydrochloric acid and iron filings?
When iron (Fe) reacts with hydrochloric acid (HCl), a single displacement reaction occurs. The iron displaces the hydrogen from the acid, resulting in the formation of iron(II) chloride (FeCl2) and the evolution of hydrogen gas (H2).
60
Which metals are added to chromium and iron to produce stainless steel?
Stainless steel is an alloy of iron, chromium, and often nickel. Chromium is essential for providing corrosion resistance by forming a passive oxide layer, while nickel is frequently added to improve the mechanical properties, ductility, and corrosion resistance of the austenitic stainless steel grades.
