Chemistry 2024 Jamb Examination

Water reacts with sodium to form sodium hydroxide, an alkali, and also reacts with anhydrous copper(II) sulphate to form the hydrated blue compound CuSO4·5H2O. This reaction demonstrates water's ability to act as a reactant in both cases, whereas acids, bases, or solvents would not produce the same colour change.

The reaction shows nuclear transmutation. The mass number decreases by 1 and the atomic number increases by 1. This indicates that X is a beta particle (β−) which converts a neutron into a proton, thereby increasing the atomic number by 1 without changing the mass number.

Sublimation occurs when a solid changes directly to gas. NH₄Cl, I₂, and S₈ can sublime under heat, but CaCO₃ decomposes into CaO and CO₂ instead of subliming. Therefore, CaCO₃ does not undergo direct solid-to-gas transition.

Oxidation is defined as the loss of electrons. As electrons are lost, the oxidation number of the species increases. Reduction would correspond to a decrease in oxidation number, and acting as an oxidizing agent is a separate concept.

A strong acid is one that fully dissociates in aqueous solution. Hydrochloric acid ionizes completely into H+ and Cl− ions, which is why it is considered strong. Partial ionization would indicate a weak acid.

In K₄Fe(CN)₆, iron has an oxidation state of +2 because the overall charge is neutral and each cyanide ligand is -1. Therefore, the correct name is potassium hexacyanoferrate(II).

Aluminium oxide (Al₂O₃) is amphoteric because it can react both with acids (forming salts) and with bases (forming aluminates). The other oxides are either acidic or basic in nature.

Saponification, cracking, and polymerization are all processes related to petroleum and its derivatives. Fermentation is related to biochemical processes, typically converting sugars into alcohol, and is not used in the petroleum industry.

Kerosene is a non-polar organic solvent. It effectively dissolves non-polar substances like paints, gums, and fats, with paints being the most common industrial use as a solvent medium.

Spontaneity of a reaction is determined by Gibbs free energy (ΔG). A negative ΔG indicates a reaction is spontaneous. While negative enthalpy and positive entropy changes favour spontaneity, the key criterion is that the free energy change is negative.