Chemistry exam trends & analysis (2019–2025)

Showed sudden jumps for other species; didn't scale changes by stoichiometry.

Solved a quadratic instead of using the small-x approximation; calculator/substitution errors.

Didn't use Ksp values to justify solubility differences; unbalanced ionic equations.

Used mass of ethanol not water in mcAT; wrong ethanol formula/atomic masses.

Did not identify soot as C(s); unbalanced equations; failed to link soot to insufficient oxygen

Made general ion statements; didn't name Ba2+/Cl- at equivalence; described rather than explained.

Could not distinguish a structural isomer from a functional isomer.

Referred to numbers' size on a number line instead of energy/entropy meaning; contradictory statements.

Didn't read spectra values against the data sheet; omitted required information.

Explained how rather than why AAS works; used generalised, non-specific terminology.

Could not write a balanced net ionic precipitation equation; failed to identify source ions

Didn't state each technique's key use or how spectra work together.

Did not use polymer-section conventions or give each carbon four bonds in the structure.

Not explicit about which acid; failed to explain effects of acid strength and concentration

Did not write a balanced equation, identify excess reactant, or use the 1:2 ratio.

Misunderstood back titration; used AgCl molar mass instead of Cl; mishandled excess reagent

Weak on haloalkane reactions; omitted reactivity tests; vague spectroscopic data without wavelengths.

Weak equations; attributed conductivity rise to low OH- conductivity rather than small [OH-] change.

Used an incorrect Kw value rather than the data-sheet value.

Confused intra- and intermolecular forces; wrong IMF terminology; missed chain-length dispersion link

Wrote an unbalanced equation; rounded mid-calculation; didn't use periodic-table masses.

Stated everything about the models instead of assessing advantages/limitations; poor balanced equations.

Misconstrued ethene oxidation as polymerisation/combustion; thought water was a coolant not a reagent

Used q incorrectly; confused dH with q; wrongly assumed c of water

Gave physical tests instead of chemical tests to distinguish the isomers.

Poorly drawn amine structures; H looked like N; pencil not fully erased

Made general Le Chatelier statements; didn't specify OH-/H3O+ effects or buffer composition.

Misidentified compound; missed carbonyl-adjacent 13C; confused broad COOH vs OH IR peaks; wrong molecular ion

Did not show NH4Cl is a salt not an Arrhenius acid; omitted ion charges in equations

Not removing the outlier; rounding too early; mis-sequencing mole ratios through the back-titration steps.

Could not distinguish qualitative from quantitative analysis or link to specific ions