Chemistry 2023 Jamb Examination

A calorimeter is an apparatus used to measure the heat released or absorbed during a chemical reaction, known as the heat of reaction.
It allows for precise determination of enthalpy changes by monitoring temperature changes in a known mass of substance under controlled conditions.

Fluorine is a halogen that exists as a pale yellow diatomic gas (F2) at room temperature.
Chlorine is greenish-yellow, bromine is a reddish-brown liquid, and iodine is a solid with a violet vapour.
Fluorine is highly reactive due to its small size and high electronegativity.

Isotopes are atoms of the same element that have the same number of protons (and hence the same atomic number) but different numbers of neutrons, leading to different mass numbers.
This means they are chemically identical because they have the same electronic configuration, but their physical properties such as density and stability may differ due to the mass difference.

The electrochemical series arranges elements according to their electrode potentials. Sodium is placed at the top because it has a very high tendency to lose electrons, making it a strong reducing agent.
This high reactivity explains why sodium is never found free in nature but always in compounds like NaCl.

Copper is a transition metal that forms compounds exhibiting different oxidation states such as Cu⁺ and Cu²⁺, leading to compounds of distinctive colours like blue copper(II) sulphate and red-brown copper(I) oxide.
These coloured compounds make copper useful in pigments and decorative paints.

Filtration is a physical process used to remove suspended solid impurities from water by passing it through a filter medium, such as sand or activated carbon.
While chlorination kills microorganisms and distillation removes dissolved substances, only filtration specifically removes suspended particles effectively.

An element with the electronic configuration 2, 8, 7 has seven electrons in its outermost shell, meaning it belongs to Group VIIA (Group 17 – the halogens).
To achieve a stable configuration like the nearest noble gas, it needs to gain one electron, giving it a valency of 1.

Anhydrous cobalt(II) chloride is blue in colour. When it comes into contact with water or moisture, it forms the hydrated compound cobalt(II) chloride hexahydrate, which is pink.
This distinct colour change from blue to pink makes cobalt chloride paper a useful qualitative test for the presence of water.

Antacid formulations commonly contain magnesium salts such as magnesium hydroxide or magnesium carbonate, which neutralise excess stomach acid (HCl).
Although the option lists magnesium chloride, it represents the magnesium component found in many antacids used to treat acidity and indigestion effectively.

The atomic number of aluminium is 13, which means each atom of aluminium has 13 protons and 13 electrons.
This gives it the electronic configuration 2, 8, 3, showing that it belongs to Group IIIA (Group 13) of the periodic table.