Haematite is an iron ore (Fe2O3), Cassiterite is the primary ore of tin (SnO2), Cryolite is a sodium aluminium fluoride (Na3AlF6) used in aluminium extraction, and Argentite is a silver sulfide ore (Ag2S). Matching these yields: a-4, b-2, c-1, d-3.
82
Which of the following metals are considered noble and do not react with air under standard conditions?
Gold and platinum are noble metals with very high standard reduction potentials, making them highly resistant to oxidation and corrosion by atmospheric oxygen. While silver is relatively stable, it can react with sulfur compounds in the air to form tarnish, making gold and platinum the most inert choices provided.
83
Which of the following metals is resistant to reaction with nitric acid?
Gold is a noble metal and is highly resistant to oxidation by nitric acid alone. It requires a mixture of concentrated nitric acid and hydrochloric acid, known as aqua regia, to dissolve it by forming a complex ion.
84
What is the defining characteristic of transition elements in terms of their electronic structure?
Transition elements are defined as elements that have a partially filled d-subshell in their neutral or common oxidation states. This corresponds to having incomplete d-orbitals in the penultimate shell (n-1) while the outermost shell (n) is also partially filled or involved in bonding.
85
To which block of the periodic table does the element with atomic number 57 belong?
The element with atomic number 57 is Lanthanum. Its electronic configuration is [Xe] 5d1 6s2. Because the last electron enters the 5d orbital, Lanthanum is classified as a d-block element. Although it is often grouped with the lanthanides (which are f-block elements), Lanthanum itself is technically the first element of the d-block in the sixth period.
86
Which of the following metals cannot be extracted from its ore using carbon reduction?
Highly reactive metals like sodium have a stronger affinity for oxygen than carbon does. Therefore, carbon cannot reduce sodium oxide to metallic sodium. Such metals must be extracted using electrolytic reduction of their molten salts, whereas less reactive metals like iron or copper can be reduced by carbon.
87
What is the correct increasing order of acidity for the oxides of Manganese (Mn)?
The acidity of metal oxides increases with the oxidation state of the metal. In MnO, Mn is in the +2 state (basic). In MnO2, Mn is in the +4 state (amphoteric). In Mn2O7, Mn is in the +7 state (acidic). Therefore, the acidity increases as the oxidation state increases: MnO < MnO2 < Mn2O7.
88
What is the specific term for an alloy that contains mercury as one of its constituent metals?
An amalgam is defined as an alloy of mercury with one or more other metals. These materials can be solid, liquid, or paste-like depending on the proportion of mercury. Amalgams are commonly used in dentistry and in various chemical extraction processes due to the unique ability of mercury to dissolve other metals.
89
Which metal, represented by its chemical symbol, is commonly used to manufacture incandescent light bulb filaments?
Tungsten (symbol W) is used for filaments due to its exceptionally high melting point (approx. 3422°C), which allows it to glow white-hot without melting. Fe is Iron, Ag is Silver, and 'An' is not a standard chemical symbol for a metal.
90
Identify the first metal historically utilized by human civilization.
Copper was the first metal to be extensively used by humans, marking the beginning of the Copper Age (Chalcolithic period). It was relatively easy to extract from its ores and could be hammered into tools and ornaments before the development of smelting and alloying techniques like bronze or iron working.
