2015 JAMB CHEMISTRY PAST QUESTIONS AND ANSWERS

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

Methyl methanoate is an ester, and ethyne is an alkyne with a triple bond.

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

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

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

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

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

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

Ionization energy, electronegativity, and electron affinity increase, while atomic radius decreases.

Weighted averages for isotope percentages yield an atomic mass slightly higher than 16.

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

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

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

Alkaline pyrogallol selectively absorbs oxygen, explaining weight increase. Inert gases like nitrogen and argon are unaffected.

Chlorination kills bacteria and ensures water safety, addressing microbial contamination rather than hardness issues or odors.

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

Oil spills disrupt marine ecosystems, killing aquatic life and harming biodiversity.

Dissolution processes absorb heat, leading to increased solubility as thermal energy breaks intermolecular forces.

Hydrogen bonding in alkanols raises boiling points compared to alkanes with only Van der Waals forces.

Use the neutralization equation $n_{\text{H}2\text{SO}4} = \frac{V \times C{\text{NaOH}}}{2V{\text{acid}}}$, solving for molarity.

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

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

AgI decomposes fastest, followed by AgBr, then AgCl. Their photochemical sensitivity decreases in this order.

Displacement indicates M is more electropositive than Zn, placing it higher in the activity series.

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

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

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

Strong intermolecular forces maintain fixed positions, defining the solid state.

No change indicates saturation, as no more solute can dissolve under existing conditions.

Fluorine’s configuration has one unpaired electron in the 2p orbital, following Hund’s rule.

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.

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

The presence of water forms hypochlorous acid, a strong oxidizing agent responsible for bleaching.

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

Aluminum forms a protective oxide layer, preventing reaction with trioxonitrate(V) acid.

Aromatic compounds like benzene are produced during polymerization of ethyne under these conditions.

Fermentation involves enzymatic breakdown of starch into ethanol, commonly used in alcohol production.

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