Chemistry 2021 Jamb Examination

Zymase is a complex of enzymes produced by yeast that catalyses the conversion of glucose into ethanol and carbon dioxide during fermentation. This biochemical process occurs under anaerobic conditions and is widely used in brewing and wine-making industries.
Maltase converts maltose into glucose, diastase converts starch into maltose, and invertase converts sucrose into glucose and fructose.

The compound (CH₃)₂CHCH₂Br has a branched chain containing four carbon atoms with a bromine atom attached to a primary carbon atom next to an isopropyl group. This structure corresponds to isobutyl bromide.
It differs from normal butyl bromide, which has a straight-chain structure.

Albert Einstein proposed the mass–energy equivalence principle expressed by the famous equation \(E = mc^2\). It shows that mass can be converted into energy and vice versa. This principle underlies nuclear reactions such as fission and fusion.
Boyle formulated Boyle’s law, Lavoisier worked on the law of conservation of mass, and Avogadro is known for Avogadro’s law.

The compound HC≡CCH₃ consists of three carbon atoms with a triple bond between the first and second carbons. Its IUPAC name is prop-1-yne, but its common name is methyl acetylene.
It belongs to the alkyne family with one triple bond and is used in organic synthesis and welding.

In CuCO₃, copper exists in the +2 oxidation state because carbonate (CO₃) has a charge of -2. Therefore, the compound is named copper(II) carbonate.
There is no stable copper(III) or copper(I) carbonate under normal conditions.

The breathalyser test for alcohol detection uses a chemical reaction between ethanol and potassium dichromate in the presence of sulphuric acid. The dichromate ion is reduced from orange (Cr⁶⁺) to green (Cr³⁺) chromium ions.
This colour change indicates the presence of alcohol in the breath.

A mixture consists of two or more substances physically combined without fixed proportions. Air, milk, and cement are mixtures of gases, liquids, or solids respectively.
Mercury, however, is a pure element and not a mixture, existing as a single metallic element under normal conditions.

Bromine (Br₂) is the only non-metal that is liquid at room temperature (about 25°C). It has a reddish-brown colour and easily vaporises into a red vapour.
Chlorine and helium are gases, while phosphorus is a solid at room temperature.

Chemical changes involve formation of new substances with different properties. Cooking and digestion of food both involve chemical reactions that change the composition of the substances involved.
Freezing and heating of water are physical changes because the chemical composition of water (H₂O) remains unchanged.

Nitrogen has seven protons and seven neutrons in its most common isotope, giving an atomic mass of 14 units.
Therefore, the atomic weight of nitrogen is approximately 14, which is used in chemical calculations involving molecular masses.