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Methane (CH\(_4\)) has a tetrahedral shape with four equivalent C-H bonds and bond angles of 109.5 degrees. The tetrahedral shape of methane can be explained using the Valence Shell Electron Pair Repulsion (VSEPR) theory, which states that electron pairs around an atom will arrange themselves to minimize repulsion. The carbon atom in methane undergoes sp3 hybridization, meaning that it combines one s orbital and three p orbitals to form four equivalent sp3 hybrid orbitals.

In solids, the particles (atoms, molecules, or ions) are closely packed together due to strong intermolecular forces. These forces are strong enough to overcome the thermal energy of the particles, preventing them from moving freely. Strong intermolecular forces of attraction are primarily responsible for the definite shapes and volumes of solids because they hold the constituent particles in fixed positions.

Sugar can be separated from its impurities in a solution primarily through crystallization, a process that allows for the separation of pure solute (sugar) from the solvent (water). Separation by evaporation method can lead to sugar charring. Charring of sugar is a chemical change which occurs when sugar is heated, causing it to evaporate, become foggy due to water vapor, and ultimately produce a black, powdery substance called charcoal. This process involves the breakdown of sugar molecules into carbon, water, and other volatile compounds.

The electron is indeed the sub-particle of an atom that contributes the least to its mass, as its mass is significantly smaller compared to protons and neutrons, which make up the nucleus and thus account for the majority of an atom's mass.

Alkali metals readily form electrovalent bonds because they have a single valence electron that they easily lose, becoming positively charged ions, and readily react with nonmetals to form ionic compounds. Only option A has the electronic configuration that fits the description of alkali metals; 2, 8, 1

A heterogeneous mixture is a mixture in which the composition is not uniform. It consists of two or more phases. When oil and water are combined, they do not mix evenly, but instead form two separate layers. Other examples include; Soil (containing sand, pebbles, and organic matter). Blood (containing red blood cells, white blood cells, platelets, and plasma). Sand and water. Vegetable soup (you can see the different vegetables and broth) etc

Given: V\(_1\) = 100 cm\(^3\) T\(_1\) = 35\(^0\)C + 273 = 308K P\(_1\) = 750 mmHg V\(_2\) = ? T\(_2\) = 35\(^0\)C + 273 = 308K P\(_2\) = 100 mmHg According to Boyle's law, the volume of a given mass of gas is inversely proportional to pressure, provided temperature remains constant. Since temperature remains unchanged, it means T\(_1\) = T\(_2\), invariably meaning that temperature remains constant. So, applying Boyle's law, P\(_1\) V\(_1\) = P\(_2\)V\(_2\) ( At constant temperature) V\(_2\) = \(\frac{{P_1}{V_1}}{P_2}\) V\(_2\) = \(\frac{{750}\times{100}}{100}\) V\(_2\) = 750cm\(^3\)

Radioactive isotopes are used in the preparation of drugs, specifically in the form of radiopharmaceuticals, which are drugs containing radioactive isotopes used for both diagnosis and treatment of various medical conditions such as treatment of cancer. Also, radioactive isotopes, acting as tracers, are used to detect leaks in water mains, with gamma-emitting isotopes added to the water, and their accumulation in the soil around a leak detected by radiation detectors. Radioactive isotopes, particularly carbon-14, are used in a method called radiocarbon dating to determine the age of ancient tools and other organic materials, up to approximately 60,000 years old.

It's important to take note of "valence shell" used in the presentation of the question. Electronic configuration and valence shell electronic configuration are not the same. Electronic configuration describes the arrangement of all electrons in an atom, while valence shell electronic configuration focuses specifically on the electrons in the outermost shell, which are the valence electrons. Hence; Option D carries the answer as specified in the question.

Density = \(\frac{mass}{volume}\) Recall that the molar volume of gases at s.t.p = 22.4 dm\(^3\) ∴ 1.98 = \(\frac{mass}{22.4}\) Mass = 1.98 x 22.4 Molecular mass = 44.35g

When pure aluminum metal is heated to red-hot in the presence of nitrogen gas, it undergoes a chemical reaction, forming aluminum nitride (AlN). The reaction can be represented by the following balanced chemical equation: 2 Al(s) + N₂(g) → 2 AlN(s).

When ammonia (NH\(_3\)) gas reacts with hydrogen chloride (HCl) gas, they form solid ammonium chloride (NH\(_4\)Cl), observable as white fumes or clouds. The reaction is a neutralization reaction where ammonia, acting as a base, accepts a proton (H+) from the acid, hydrogen chloride. NH\(_3\)(g) + HCl(g) → NH\(_4\)Cl(s)

Increasing temperature in the Haber process decreases the yield of ammonia because the forward reaction is exothermic, and Le Chatelier's principle states that increasing temperature shifts the equilibrium position towards the endothermic (reverse) direction, reducing ammonia production.

Concentrated tetraoxosulphate(VI) acid, a hygroscopic liquid is a very strong drying agent as it absorbs moisture from the air, and becomes diluted to about three times its original volume. It can be used to dry all gases except ammonia and Hydrogen sulphide. Consequently, for drying SO₂ gas, concentrated sulphuric acid (H₂SO₄) is a suitable drying agent, as it effectively absorbs water vapour without reacting with the sulphur dioxide. On the contrary, concentrated sulphuric acid (H₂SO₄) cannot be used to dry hydrogen bromide (HBr) gas because it is a strong oxidizing agent that will react with HBr, oxidizing it to bromine (Br₂) and sulphur dioxide (SO₂). Also, H₂S cannot be dried using concentrated tetraoxosulphate(VI) acid (H₂SO₄) because it reacts with H₂S, producing water, sulphur dioxide, and elemental sulphur, thus failing to serve its purpose of drying. Ammonia cannot be dried using concentrated sulfuric acid (tetraoxosulphate(VI) acid) because they react to form ammonium sulfate, a solid, rather than drying the ammonia.

In a closed system, as a reaction proceeds, the concentrations of reactants and products change until the system reaches a state where the forward and reverse reactions are occurring at the same rate. Reactions in a closed system naturally tend towards a state of equilibrium, where the rates of the forward and reverse reactions are equal, and the net change in concentrations of reactants and products is zero.