JAMB Chemistry 2012
Questions & Answers

The contact process uses vanadium(V) oxide (V₂O₅) as a catalyst to convert SO₂ to SO₃: 2SO₂ + O₂ → 2SO₃.

Destructive distillation of coal produces coke, coal gas, ammonia liquor, and coal tar. Coke and ammonia liquor are standard products.

Potassium trioxonitrate(V) (KNO₃) acts as an oxidant in gunpowder, providing oxygen to support the combustion of charcoal and sulphur.

In concentrated NaCl solution, Cl⁻ ions are oxidized at the anode: 2Cl⁻ → Cl₂ + 2e⁻, producing chlorine gas.

ΔH = ΣΔH_f(products) - ΣΔH_f(reactants). -1428 = [2(-396) + 2(-286)] - [ΔH_f(C₂H₄) + 0]. Solving: ΔH_f(C₂H₄) = +52 kJ/mol.

In 2H₂S + SO₂ → 2H₂O + 3S, H₂S is oxidized (S²⁻ to S) and SO₂ is reduced (S⁴⁺ to S), making it a redox reaction.

Dissolving NaOH in water is exothermic, releasing heat, so the heat of solution is negative (ΔH < 0).

Increasing the surface area of reactants increases the frequency of collisions between particles, thus increasing the reaction rate.

In Na₂S₂O₃, Na = +1, O = -2. Let the oxidation number of S be x. 2(+1) + 2x + 3(-2) = 0 → 2 + 2x - 6 = 0 → 2x = 4 → x = +2 per S, but the average for the thiosulphate ion is +4 when considering the structure.

According to Graham’s law, the rate of diffusion is inversely proportional to the square root of molar mass. NH₃ (molar mass 17 g/mol) is the lightest, so it diffuses the fastest.

Mass = moles × molar mass = 3 × 58.5 = 175.5 g.

Covalent compounds typically have low boiling points due to weak intermolecular forces (e.g., van der Waals forces) compared to ionic compounds.

Mg + 2HCl → MgCl₂ + H₂. Magnesium reacts with dilute HCl to produce magnesium chloride and hydrogen gas.

Ozone is a secondary pollutant formed in the atmosphere through reactions involving primary pollutants like nitrogen oxides and volatile organic compounds in the presence of sunlight.

HCl is a strong acid, so [H⁺] = 0.001 M. pH = -log(0.001) = 3.

Fehling’s solution is reduced by aldehydes to form a red precipitate of copper(I) oxide, indicating the presence of an aldehyde.

Sublimation is the process where a solid transitions directly into a gas without passing through the liquid phase, e.g., iodine or dry ice.

Sodium, a Group 1 metal, is the most electropositive among the options because it readily loses its valence electron to form a positive ion.

Propanol (C₃H₇OH) reacts with ethanoic acid (CH₃COOH) in the presence of a catalyst (e.g., H₂SO₄) to form propyl ethanoate (CH₃COOC₃H₇) and water.

Acids turn blue litmus paper red due to their ability to release H⁺ ions in solution, which lowers the pH.

Moles of C = 60/12 = 5, H = 13.3/1 = 13.3, O = 26.7/16 = 1.67. Ratio = 5:13.3:1.67 = 3:8:1. Empirical formula = C₃H₈O.

At equilibrium, the rate of the forward reaction equals the rate of the reverse reaction, and the concentrations of reactants and products remain constant.

Zn + H₂SO₄ → ZnSO₄ + H₂. Zinc reacts with dilute H₂SO₄ to produce zinc sulphate and hydrogen gas.

The Ostwald process uses a platinum catalyst to oxidize ammonia to nitric oxide: 4NH₃ + 5O₂ → 4NO + 6H₂O.

In KClO₃, K = +1, O = -2. Let Cl = x. 1 + x + 3(-2) = 0 → 1 + x - 6 = 0 → x = +5.

Alkynes are unsaturated hydrocarbons with a carbon-carbon triple bond, making them reactive in addition reactions.

Volume = moles × molar volume = 2 × 22.4 = 44.8 dm³.

Biuret reagent turns violet in the presence of proteins due to the reaction with peptide bonds.

Nitrogen oxides are primarily produced by the combustion of fossil fuels in vehicles and power plants, where high temperatures cause nitrogen and oxygen to react.

Nitrogen does not trap heat in the atmosphere, whereas methane, carbon dioxide, and water vapour are greenhouse gases.

Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. Calcium hydroxide reacts with carbon dioxide to form calcium carbonate and water.

Sodium, a highly reactive Group 1 metal, reacts with cold water to produce sodium hydroxide and hydrogen gas: 2Na + 2H₂O → 2NaOH + H₂.

Empirical formula mass of CH₂ = 12 + 2 = 14 g/mol. n = molar mass/empirical mass = 42/14 = 3. Molecular formula = (CH₂)₃ = C₃H₆.

In the electrolysis of molten NaCl, Na⁺ is reduced to Na at the cathode (Na⁺ + e⁻ → Na), and Cl⁻ is oxidized to Cl₂ at the anode (2Cl⁻ → Cl₂ + 2e⁻).

Concentrated H₂SO₄ acts as a dehydrating agent in esterification, removing water to drive the reaction forward: C₂H₅OH + CH₃COOH ⇌ CH₃COOC₂H₅ + H₂O.

Benzene (C₆H₆) has a planar ring structure with delocalized π-electrons, making it aromatic and relatively stable, favoring substitution over addition reactions.

Moles of NaOH = 4/40 = 0.1 mol. Volume = 500 cm³ = 0.5 dm³. Molarity = moles/volume = 0.1/0.5 = 0.2 M.

Ethanol and water have different boiling points (78°C and 100°C, respectively), so fractional distillation can separate them based on this difference.

A catalyst increases the rate of both the forward and reverse reactions equally by lowering the activation energy, but it does not shift the equilibrium position.

Ethanol (C₂H₅OH) reacts with sodium to produce sodium ethoxide and hydrogen gas: 2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂. The other compounds do not produce a gas with sodium.