2022 JAMB CHEMISTRY PAST QUESTIONS AND ANSWERS

The nucleus of an atom contains protons (positively charged particles) and neutrons (neutral particles). Electrons orbit around the nucleus and are not found within it. Ions are charged atoms/molecules, not subatomic particles.

In IUPAC nomenclature, the longest carbon chain determines the base name. The structure shows a chloro group and methyl group on the same carbon, making it 2-chloro-2-methylbutane. The other options incorrectly identify the position or number of substituents.

Vanadium(V) oxide is the primary industrial catalyst used in the Contact Process for manufacturing sulfuric acid, where [SO_2] is converted to [SO_3]. Other metal oxides listed are not as effective for this specific reaction.

The stability of a salt to heat determines which preparation method is most suitable. Some salts decompose when heated, requiring different preparation methods, while others are stable enough for direct heating methods.

Phosphorus, sulfur, and carbon all form acidic oxides with oxygen. Chlorine forms oxides that are acidic in nature. The question appears to have an error as all options form acidic oxides.

To find neutrons: Mass number – Atomic number = Number of neutrons. Here: 37 – 17 = 20 neutrons. The atomic number (17) represents protons, while mass number (37) is the sum of protons and neutrons.

Zinc sulfide (ZnS) is used as a phosphor coating in fluorescent tubes due to its fluorescent properties. When excited by UV light, it emits visible light through phosphorescence.

Acetic acid (CH₃COOH) reacts with carbonate solutions to produce CO₂ gas. This is a characteristic reaction of carboxylic acids with carbonates. Other options don’t react with carbonates to produce CO₂.

When NaCl dissolves in water, it causes colligative property changes: decreasing freezing point and increasing boiling point. This is due to the dissolved ions disrupting the water’s intermolecular forces.

Nitrochalk is a nitrogen-based fertilizer containing calcium nitrate and ammonium nitrate. Galena (PbS), bauxite (Al ore), and emerald (beryl) are minerals, not fertilizers.

Cu²⁺ has the highest reduction potential among the given options, making it the most easily reduced (discharged) at the cathode. The electrochemical series shows: Cu²⁺ > Sn²⁺ > Fe²⁺ > Zn²⁺

Activated charcoal in water treatment removes odors through adsorption of organic compounds and impurities that cause bad smells. It doesn’t prevent goiter, tooth decay, or directly kill germs.

Iron is reactive enough to decompose steam, producing hydrogen gas and iron oxide. Copper, tin, and lead are less reactive and cannot displace hydrogen from steam.

Amines (RNH₂) typically have fishy odors. This is characteristic of primary amines. The other options represent different organic functional groups that don’t typically have fishy smells.

For an exothermic reaction (Δ=-ve), low temperature favors forward reaction. Since the number of moles decreases, high pressure also favors forward reaction to form N₂O₄.

In this reaction, zinc loses electrons to form Zn²⁺, making it oxidized. While zinc is a reactant and a metal, the question specifically asks about its electron transfer behavior.

Alkynes can reduce ammoniacal silver nitrate (Tollens’ reagent), forming a silver mirror. This is a characteristic test for terminal alkynes. Other options don’t give this reaction.

Chlorine is a yellowish-green gas that is highly toxic and can severely damage the respiratory system. The other gases, while also harmful, don’t match all criteria (color and specific damage).

In electroplating, the object to be plated (spoon) is the cathode where metal ions are reduced. The silver rod serves as the anode, and silver nitrate solution is the electrolyte.

Ethene (C₂H₄) contains a double bond that undergoes addition reaction with bromine, decolorizing the brown bromine water. Alkanes are saturated and don’t react with bromine.

Fractional distillation separates crude oil components based on boiling points. This industrial process is fundamental to petroleum refining. Other methods don’t separate petroleum components effectively.

Converting percentages to moles: C=5.75, H=15.3, O=1.92. Dividing by smallest number (1.92): C:H:O = 3:8:1. Therefore, empirical formula is C₃H₈O.

From equation, H₂:O₂ ratio is 2:1. For 50 cm³ H₂, need 25 cm³ O₂. Given 75 cm³ O₂, excess = 50 cm³ unreacted.

NaH forms an ionic bond as Na loses an electron to H, forming Na⁺ and H⁻. Other compounds listed form covalent bonds through electron sharing.

Using Charles’ Law: V₁/T₁ = V₂/T₂. V₂ = 29.5(288/273) = 31.1 cm³. Temperature must be in Kelvin (273 + °C).

H₂SO₄ + 2NaOH has the highest ΔH as it’s a diprotic acid neutralizing two moles of base. Other reactions involve monoprotic acids or weaker bases.

The atomic number equals the number of protons, which in a neutral atom equals the number of electrons. It’s not the number of neutrons or total nucleons.

Fluorine has the highest electronegativity value (4.0 on Pauling scale) of all elements due to its small size and high nuclear charge.

Ionic bonds involve electron transfer between metals and non-metals, forming charged ions. Electron sharing describes covalent bonding, not ionic bonding.

Na + H₂O → NaOH + H₂. Sodium reacts with water to form sodium hydroxide and hydrogen gas. Other products listed are not formed in this reaction.

Nickel is the most commonly used catalyst in industrial hydrogenation of oils due to its effectiveness and lower cost compared to other options.

Sulfuric acid is a strong diprotic acid with high dissociation. Other acids listed are either weak (acetic, citric) or monoprotic (hydrochloric).

Endothermic reactions absorb energy from surroundings. Exothermic releases energy. Neutralization and displacement describe reaction types, not energy changes.

Sodium bicarbonate neutralizes acetic acid in vinegar, forming salt, water, and CO₂. It’s not an indicator and doesn’t primarily produce CO₂ or increase acidity.

Fractional distillation separates liquids based on their different boiling points. Components vaporize at different temperatures, allowing separation. Other properties like density or solubility aren’t the primary basis.

Rust formation (iron oxidation) requires both oxygen and water to occur. Neither alone is sufficient for significant rusting. The presence of both accelerates the corrosion process.

CO₂ is the primary greenhouse gas contributing to global warming through its ability to trap heat in the atmosphere. Other gases listed aren’t significant greenhouse gases.

Alcohols are characterized by the presence of an -OH (hydroxyl) group. Aldehydes (-CHO), ketones (C=O), and ethers (C-O-C) have different functional groups.

BaSO₄ (barium sulfate) is notably insoluble in water due to strong ionic lattice forces. The other salts listed are all water-soluble.

Saponification is the alkaline hydrolysis of fats/oils to produce soap. Other processes listed describe different chemical reactions not related to soap making.

When carbonates react with acids, they produce CO₂ gas as one of the products. This is a characteristic test for carbonate ions.

Potassium is most reactive with water, followed by sodium, then lithium. This follows the trend down Group 1 of increasing reactivity with atomic size.

Hydrogen is produced at the cathode (negative electrode) through reduction of H⁺ ions. Oxygen is produced at the anode. Other gases aren’t products of water electrolysis.

Acids taste sour, not bitter. Bitter taste is a characteristic of bases. Acids turn blue litmus red, react with metals to produce H₂, and form salts with bases.

Sodium hydroxide (NaOH) is a strong base that produces OH⁻ ions in solution. HCl is an acid, NaCl is neutral salt, and NH₄NO₃ is slightly acidic.