Chemistry

Joseph Black is credited with the discovery of carbon dioxide, which he called 'fixed air,' in the 1750s through his experiments on magnesium carbonate and calcium carbonate.

The chemical symbol for Iron is Fe, derived from its Latin name 'Ferrum'. This is a standard and universally accepted symbol in the periodic table.

Permanent hardness in water is caused by dissolved calcium and magnesium salts that do not precipitate on boiling. Adding sodium carbonate (washing soda) precipitates these ions as insoluble carbonates, thus removing permanent hardness.

Helium is the lightest noble gas in the periodic table, with an atomic number of 2 and atomic mass of about 4 u. Nitrogen, hydrogen, and oxygen are not noble gases, so they are incorrect options.

Graphite is considered one of the purest forms of carbon, consisting almost entirely of carbon atoms arranged in a crystalline structure. Anthracite is a type of coal containing impurities, and lampblack is a form of carbon black produced by incomplete combustion, often containing impurities as well.

Phosphorus, antimony, and arsenic are elements that commonly act as donor atoms in coordination chemistry due to their lone pairs of electrons. Aluminum, being a metal with empty orbitals, typically acts as an acceptor rather than a donor atom.

PVC (Polyvinyl chloride) is produced by the polymerization of vinyl chloride monomers. Propane and styrene are monomers for other polymers, and 'None of these' is incorrect.

Water is known to have multiple crystalline phases (ice polymorphs) under different temperature and pressure conditions. As of current scientific consensus, there are 18 recognized crystalline phases of ice, making option D correct.

In chemistry, homologous refers to compounds in a homologous series that have the same chemical properties but differ by a repeating unit, typically a -CH2- group. Therefore, 'Same Chemical Properties' is the correct interpretation.

Sodium carbonate is commonly known as washing soda, which is used in cleaning and laundry applications. The other options are incorrect: Plaster of Paris is calcium sulfate hemihydrate, and common salt is sodium chloride.

Authoritative sources including Wikipedia, Britannica, and specialized materials science references confirm that tungsten has the highest melting point of all metals, approximately 3422°C. Among the given options, 4000°C (option D) is the closest to the actual melting point, which is about 3422°C. The other options (1000°C, 2000°C, 3000°C) are significantly lower and incorrect. Therefore, option D is the best choice despite being a slight overestimate.

Copper (Cu) is a transition element because it is a d-block element with an incomplete d-subshell in its atoms or common oxidation states. Chlorine (Cl) and sulfur (S) are p-block elements and not transition metals. Therefore, option B is correct.

Bauxite is not a single chemical compound but a mixture of minerals primarily containing aluminium oxides and hydroxides such as gibbsite, boehmite, and diaspore. Therefore, it does not have a single chemical name like 'Aluminium Oxide'.

RDX is commonly known as Cyclonite, which is a powerful explosive compound. The other options do not correspond to RDX.

Gold and silver are both classified as coinage metals because they have historically been used to make coins. They are also considered noble metals due to their resistance to corrosion and oxidation. Therefore, both terms apply to these metals.

The modern periodic table currently contains 118 confirmed elements, from hydrogen (1) to oganesson (118). This is the widely accepted and standardized count in chemistry.

Chromite is the primary ore of chromium, containing chromium oxide and iron oxide, making it the main source for extracting chromium metal. The other options are unrelated substances.

Fluorine is the most electronegative element in the periodic table due to its high effective nuclear charge and small atomic radius, which strongly attracts electrons. Oxygen and bromine are less electronegative, and sodium is a metal with low electronegativity.

Chromite is the primary ore of chromium, from which chromium metal is extracted. The other options are unrelated to chromium.

The modern periodic table currently contains 118 confirmed elements, from Hydrogen (1) to Oganesson (118). This is the widely accepted and updated count in scientific literature.

The position of an element in the Periodic Table is determined by its atomic number, which is the number of protons in the nucleus of an atom. This number uniquely identifies each element and defines its place in the table.

Metals tend to lose electrons easily and thus are highly electropositive, meaning they have a tendency to donate electrons in chemical reactions. Electronegativity refers to the ability to attract electrons, which is generally low for metals.

Bromine is the only non-metal that exists as a liquid at room temperature, unlike mercury which is a metal. Phosphorus and iodine are solids at room temperature.

Chalk is primarily composed of calcium carbonate, which is the chemical name for chalk. The other options are unrelated chemical compounds.

Oil of Vitriol is the historical name for Sulphuric Acid, a strong mineral acid widely used in industry and laboratories.