2015 JAMB CHEMISTRY PAST QUESTIONS AND ANSWERS

$$\text{The average kinetic energy of a gas is directly proportional to its absolute temperature. This follows from the kinetic theory of gases.}$$

$$\text{Methyl methanoate is an ester, and ethyne is an alkyne with a triple bond.}$$

$$\text{X contains Cl}^- \text{ions as they react with Ag}^+ \text{ to form } \text{AgCl}, \text{ which is white and soluble in ammonia.}$$

$$\text{Methane is an alkane } \text{ (C}_n\text{H}_{2n+2})\text{, containing only single bonds between carbon atoms.}$$

$$\text{NH}_4\text{Cl contains ionic bonds, covalent bonds within NH}_4^+, \text{ and co-ordinate bonds within the ammonium ion.}$$

$$\text{Heating removes 4 molecules, as the residue weight corresponds to } \text{CuSO}_4. \text{ Calculations verify this.}$$

$$\text{Boyle’s law states } P \propto \frac{1}{V} \text{ when } T \text{ is constant, forming a hyperbolic curve.}$$

$$\text{Titration data calculates K}_2\text{CO}_3 \text{ content via molarity and sample weight relationships.}$$

$$\text{Ionization energy, electronegativity, and electron affinity increase, while atomic radius decreases.}$$

$$\text{Weighted averages for isotope percentages yield an atomic mass slightly higher than 16.}$$

$$\text{Atomic number 17 belongs to halogens, typically having oxidation states of } -1 \text{ (as anions) and } +7 \text{ in oxyanions like perchlorates.}$$

$$\text{Phosphorus (Group 15) has 5 valence electrons, evident from its electron configuration } 1s^2 2s^2 2p^6 3s^2 3p^3.\text{}$$

$$\text{Calculate using } PbS \text{ weight and molar mass to determine moles of H}_2\text{S, linking it to air volume percentage.}$$

$$\text{Alkaline pyrogallol selectively absorbs oxygen, explaining weight increase. Inert gases like nitrogen and argon are unaffected.}$$

$$\text{Chlorination kills bacteria and ensures water safety, addressing microbial contamination rather than hardness issues or odors.}$$

$$\text{Using molar mass } (40 g/mol),\text{ the solution has } 0.10 \text{ moles per dm}^3.\text{}$$

$$\text{Oil spills disrupt marine ecosystems, killing aquatic life and harming biodiversity.}$$

$$\text{Dissolution processes absorb heat, leading to increased solubility as thermal energy breaks intermolecular forces.}$$

$$\text{Hydrogen bonding in alkanols raises boiling points compared to alkanes with only Van der Waals forces.}$$

$$\text{Use the neutralization equation } n_{\text{H}_2\text{SO}_4} = \frac{V \times C_{\text{NaOH}}}{2V_{\text{acid}}},\text{ solving for molarity.}$$

$$\text{Stoichiometry calculates } V_{\text{acid}} \text{ using } n = \frac{\text{mass}}{\text{molar mass}},\text{ and } n_{\text{acid}} = n_{\text{base}}.\text{}$$

$$\text{pH decreases with increased } [H^+],\text{ so the solution with the highest molarity of acid contributes the lowest pH.}$$

$$\text{AgI decomposes fastest, followed by AgBr, then AgCl. Their photochemical sensitivity decreases in this order.}$$

$$\text{Displacement indicates M is more electropositive than Zn, placing it higher in the activity series.}$$

$$\text{Steam rehydrates CoCl}_2,\text{ forming CoCl}_2 \cdot 6\text{H}_2\text{O, which is pink.}$$

$$\text{Reactions with decreased gas volume shift toward fewer molecules under pressure, as seen in 2H}_2 + \text{O}_2 \rightarrow 2\text{H}_2\text{O.}$$

$$\text{Use } \Delta H = \Sigma H_f(\text{products}) – \Sigma H_f(\text{reactants})\text{, where CO}_2 = -393 \text{ and CO = -110 kJ/mol.}$$

$$\text{Strong intermolecular forces maintain fixed positions, defining the solid state.}$$

$$\text{No change indicates saturation, as no more solute can dissolve under existing conditions.}$$

$$\text{Fluorine’s configuration has one unpaired electron in the 2p orbital, following Hund’s rule.}$$

$$\text{Oxygen is used in blast furnaces to oxidize and remove impurities as oxides, improving steel quality.}$$

$$\text{H}_2\text{S is a reducing agent, donating electrons during chemical reactions like metal precipitation.}$$

$$\text{HNO}_3 \text{ is an oxidizer in rocket fuel due to its high reactivity and energy release when combined with fuel.}$$

$$\text{The presence of water forms hypochlorous acid, } \text{a strong oxidizing agent responsible for bleaching.}$$

$$\text{Mineral acids stabilize H}_2\text{O}_2 \text{ by minimizing decomposition into water and oxygen.}$$

$$\text{Aluminum forms a protective oxide layer, preventing reaction with trioxonitrate(V) acid.}$$

$$\text{Aromatic compounds like benzene are produced during polymerization of ethyne under these conditions.}$$

$$\text{Fermentation involves enzymatic breakdown of starch into ethanol, commonly used in alcohol production.}$$

$$\text{Endothermic reactions are denoted as } +\Delta H \text{ because they absorb energy from surroundings.}$$

$$\text{Lower temperatures favor the exothermic forward reaction, increasing } \text{SO}_3 \text{ concentration.}$$