Chemistry 2022 Jamb Examination

A solid-gas mixture consists of tiny solid particles dispersed in a gas. Smoke fits this description because it contains solid carbon or soot particles suspended in air.
Milk is a liquid-liquid emulsion, kerosene is a homogeneous liquid mixture, and soil is a solid-solid mixture. Hence, smoke is the correct representation of a solid-gas mixture.

According to the Aufbau principle, electrons fill orbitals in order of increasing energy, starting from the lowest available energy level. The correct electronic configuration should follow Hund’s rule, which states that electrons occupy degenerate orbitals singly before pairing up.
The configuration 1s² 2s² 2pₓ² 2pᵧ¹ 2$p_z$¹ 3s⁰ shows this pattern correctly, as electrons occupy each 2p orbital singly before pairing begins. Therefore, it follows the correct filling order.

Wrought iron is produced by oxidising impurities such as carbon from cast iron. This is achieved by heating cast iron with haematite (Fe₂O₃) in a furnace. The haematite acts as an oxidising agent, converting carbon to carbon dioxide and purifying the iron.
Magnetite is another iron ore but is not typically used for this refining process. Calcium trioxosilicate(IV) (slag) is a by-product, not a reactant.

In a blast furnace, hot air is blown in through the tuyeres — small nozzles located near the base of the furnace. This air reacts with coke to produce carbon dioxide and heat, which maintains the high temperature required for reduction reactions.
Valves and arcs are not used for air injection in this context, and the open-hearth process is a different method for steel production.

Carbon(IV) oxide (CO₂) has a linear structure represented as O=C=O. Each double bond between carbon and oxygen contains two bonding pairs of electrons.
Therefore, the total number of bonding pairs is 4 (2 in each double bond).

Structural isomers have the same molecular formula but different arrangements of atoms. 2-methylprop-1-ene (C₄H₈) and but-2-ene (C₄H₈) share the same molecular formula but differ in the position of the double bond and the branching of the carbon chain.
Hence, they are structural isomers.

Alkanes, being saturated hydrocarbons, burn readily in air to produce energy, carbon dioxide, and water. Their high combustion energy makes them suitable as fuels for domestic and industrial purposes (e.g., methane, propane, and butane).
They are not primarily used for hydrogenation or textile applications.

Using the dilution formula \(C_1V_1 = C_2V_2\):
\(C_1 = 2.0\), \(V_1 = 10\), \(C_2 = 0.5\).\[2.0 \times 10 = 0.5 \times V_2\]\[V_2 = 40\,\text{dm}^3\]The total volume after dilution is 40 dm³. The volume of water added = 40 − 10 = 30 dm³.
Thus, 30 dm³ of water should be added.

On Earth, nitrogen constitutes about 78% of the atmosphere and oxygen about 21%. Carbon dioxide makes up less than 0.04%.
Therefore, nitrogen (N₂) and oxygen (O₂) are present in higher proportions on Earth than on planet X.

Hard water contains high concentrations of calcium (Ca²⁺) and magnesium (Mg²⁺) ions. These ions come from dissolved salts such as calcium hydrogen carbonate and magnesium sulphate.
They interfere with soap lathering and cause scale formation in pipes and boilers.
Nitrogen, phosphorus, and helium ions do not contribute to water hardness.