Chemistry 2020 Jamb Examination

The given configuration ends with 3p³, which corresponds to phosphorus (atomic number 15).
In the 3p orbital, there are three electrons, each occupying separate orbitals according to Hund’s rule — which states that electrons occupy degenerate orbitals singly before pairing.
Hence, there are three unpaired electrons in the element.

Fractional distillation separates components of a mixture based on differences in boiling points. Liquid air is a mixture of gases with different boiling points, so fractional distillation is used to separate nitrogen, oxygen, and argon from it.
Other listed methods such as crystallisation or evaporation apply to solids in solution, not gases.

Duralumin is an alloy primarily composed of aluminium (over 90%), copper, manganese, and magnesium. It is lightweight yet strong, making it suitable for aircraft construction.
Thus, manganese and magnesium are the additional elements in Duralumin.

Polysaccharides are complex carbohydrates formed by condensation of many monosaccharide units. Starch is a typical polysaccharide made up of multiple glucose molecules joined by glycosidic bonds.
Dextrose, mannose, and glucose are all monosaccharides.

At S.T.P, 1 mole of any gas occupies 22.4dm³.
Molar mass of CH₄ = 16g/mol → 8g = 0.5mol → 0.5 × 22.4 = 11.2dm³ (verified).
Molar mass of CH₃CH₂CH₃ = 44g/mol → 22g = 0.5mol → 0.5 × 22.4 = 11.2dm³.
Hence, both gases occupy the same volume at S.T.P.

Concentrated tetraoxosulphate(VI) acid (H₂SO₄) causes severe burns on contact with skin. The immediate treatment is to flush the affected area with plenty of cool running water to dilute and remove the acid.
Neutralising with alkali can worsen the injury due to heat generated in neutralisation.

Charles’ law states that at constant pressure, the volume of a fixed mass of gas is directly proportional to its absolute temperature (V ∝ T).
The graph of volume against temperature (Kelvin) is a straight line, illustrating Charles’ law.

The element with atomic number 17 is chlorine (Cl). It has seven valence electrons and can gain one electron to achieve a stable octet (oxidation number -1) or lose electrons in compounds to show positive oxidation states up to +7.
Hence, possible oxidation numbers are -1 and +7.

Destructive distillation involves heating a substance (like coal) in the absence of air. This breaks down the coal into several useful products — coal gas, coal tar, ammoniacal liquor, and coke.
It is an industrial process for obtaining fuel and chemical feedstocks.

The ash extract from burnt plant material contains potassium carbonate, which acts as an alkali. When palm oil (a fat) reacts with this alkali, saponification occurs, producing soap and glycerol.
Thus, the ash provides the alkaline medium necessary for soap formation.