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The branch of science that deals with the nature and properties of substances and how one substance can be converted to another is known as Chemistry. Chemistry studies the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions, including how one substance can be transformed into another.

Hund's rule states that the lowest energy state of an atom or molecule is when the spins of its electrons are aligned as much as possible. This means that electrons in the same orbital have the same spin before pairing up with opposite spins. Each orbital in a subshell is singly occupied or filled with one electron first before any orbital is doubly occupied.

Oxidation number of Cr in Na\(_2\)Cr\(_2\)O\(_7\) = 0 2(Na) + 2Cr + 7(O) = 0 Oxidation state of Na = +1, O = - 2 So, 2(+1) + 2Cr + 7(-2) = 0 +2 + 2Cr - 14 = 0 +2 - 14 + 2Cr = 0 - 12 + 2Cr = 0 2Cr = 12 Cr = \(\frac{12}{2}\) Cr = + 6

Bauxite is considered the most important ore of aluminum; it is the primary source from which aluminum is extracted globally. Bauxite ore (Al\(_2\)O\(_3\). xH\(_2\)O) is the major source of aluminium till date which is a mixture of hydrated aluminium oxide. Both haematite and magnetite are ores of Iron. Monazite is a phosphate mineral that contains rare earth elements and thorium. It's often found in sand and gravel deposits, and can be red, brown, or green in color.

Bases turn red litmus paper blue. They are also slippery to touch.

When a concentrated sodium chloride solution is electrolyzed using carbon electrodes, the primary product formed is chlorine gas at the anode (positive electrode), while hydrogen gas is produced at the cathode (negative electrode). At the anode: Chloride ions (Cl-) are oxidized to form chlorine gas (Cl\(_2\)). At the cathode: Water molecules are reduced to form hydrogen gas (H\(_2\)) and hydroxide ions (OH-). The overall reaction produces sodium hydroxide solution alongside the chlorine and hydrogen gases.

When ethanol reacts with excess acidified potassium dichromate (K\(_2\)Cr\(_2\)O\(_7\)), it gets oxidized to ethanoic acid (acetic acid), with the color of the solution changing from orange to green as the chromium ions are reduced during the oxidation process; this reaction is a common test for alcohols due to the visible color change. CH\(_3\)CH\(_2\)OH + K\(_2\)Cr\(_2\)O\(_7\) → CH\(_3\)COOH

When an ammonium salt dissolves in water, the resulting solution is acidic. Ammonium ions (NH\(_4\)\(^+\)) act as a weak acid when dissolved in water, donating a proton to water molecules and creating hydronium ions (H\(_3\)O\(^+\), which lowers the pH and makes the solution acidic.Consequently, option B is correct since the pH of solution formed will be less than 7 not greater than 1 because greater than 1 can mean that it is alkaline. Ammonium salts decompose when heated, typically releasing ammonia gas as one of the products. Ammonium salts break down into their constituent components, like ammonia and the corresponding acid, when exposed to heat. For example, ammonium chloride (NH\(_4\)Cl) decomposes into ammonia (NH\(_3\)) and hydrogen chloride (HCl) when heated. Ammonium salts are generally very soluble in water; most simple ammonium salts readily dissolve in water, making them considered highly soluble. Which makes the statement incorrect.

Solid ethanedioic acid (also known as oxalic acid) is typically purified through a process called crystallization where the impure solid is dissolved in a hot solvent (usually water), then allowed to cool slowly, causing the purer crystals to precipitate out while leaving impurities behind in the solution; this process can be repeated multiple times for further purification.

To identify an alkanoic acid, look for the presence of the carboxyl functional group (-COOH) in the molecule, which is the key indicator of an alkanoic acid (also known as a carboxylic acid).

The primary intermolecular force between ethanol molecules is hydrogen bonding. Hydrogen bonding is a strong type of dipole-dipole attraction. Other intermolecular forces present in ethanol is the London dispersion forces or Van der waal's force. Van der Waals forces of attraction are present in ethanol molecules, alongside stronger hydrogen bonding interactions; essentially, all molecules experience some degree of van der Waals forces, making them present in ethanol as well.

If 0.24g of the salt was dissolved in 100 cm\(^3\) then Xg of the salt will be dissolved in 1000 cm\(^3\) (1 dm\(^3\) ⇒ 0.24 = 100 cm\(^3\) X = 1000 cm\(^3\) Solubility of salt, X (gdm\(^{-3}\)) = \(\frac{{0.24} \times{1000}}{100}\) = 2.40 gdm\(^{-3}\)

Ni\(^{2+}\)\(_{aq}\) + Fe\(_s\) → Ni\(_s\) + Fe\(^{2+}\)\(_{aq}\) Reduction takes place from Ni\(^{2+}\) to Ni because there is a decrease in oxidation number from +2 to 0. Thus, Ni\(^{2+}\) ions are reduced to Ni Oxidation takes place from Fe to Fe\(^{2+}\) because there is an increase in oxidation number from 0 to +2. Thus, Fe is oxidized to Fe\(^{2+}\) Oxidizing agent → Ni\(^{2+}\) because oxidizing agents undergo reduction. Reducing agent → Fe because reducing agents undergo oxidation. Consequently, option D is the correct option.

Transition elements are elements having partially filled d- orbitals. The first series of transition elements ranges from Scandium to Zinc. Apart from the general properties of metals, the transition elements have in addition the following characteristics: - Variable oxidation state - Catalytic properties - Magnetic properties. - Complex ion formation

Aluminum is ideal as an alloy for aircraft because it strikes a great balance between being lightweight, strong, resistant to corrosion, and relatively easy to work with, making it perfect for building large aircraft structures while minimizing overall weight, which significantly improves fuel efficiency and performance; this is especially important due to its high strength-to-weight ratio compared to other metals like steel.