If extra pages are used, clearly number questions and ensure extra answers do not contradict the answer line.
Avoid multiple overwrites; cross out and rewrite clearly — especially for equations.
Many struggled to select the correct equation letter; multiple letters gained no credit.
(a) Photosynthesis well known. Easy
(b) Not well known; common wrong: A (neutralisation) and I (H2 combustion). Difficult
(c) Hardest part — few recognised precipitation equation. Difficult
(d) Incomplete combustion well recognised. Easy
(e) Not well known; substitution (C) commonly chosen. Difficult
(f) Not well known; displacement (F) often chosen; confusion between reaction types. Difficult
(a)(i) Aluminium generally correct — some wrote Mg/Na. Easy
(a)(ii) Reasonably well answered. Moderate
(a)(iii) Very well answered; occasional Na/S/P. Easy
(a)(iv) Amphoteric unfamiliar; Na/Mg/Si common wrong. Difficult
(a)(v) Quite well answered; Cl/Si/P seen wrong. Moderate
(a)(vi) Performed poorly; S/Na/Mg common wrong. Difficult
(b)(i) Many knew C was needed but chose 14C or just ‘carbon’. Moderate
(b)(ii) R.A.M. calc: weaker candidates averaged 24 & 25, used Periodic Table mass, rounded badly, or didn’t show working. Difficult
(c)(i) Quite well answered though 14 often seen; confusion neutrons vs nucleon no. Moderate
(c)(ii) Well answered; wrong seen: “27” as mass not atomic number. Easy
(a)(i) Unfamiliar ionic bonding style; common drawing/configuration errors.
(a)(ii) Generally good; some gave Mg charge +1 or word equations.
(a)(iii) Quite good; some wrote “heat to melt” incompletely or suggested dissolving/electrolysis.
(b) Dot-cross mostly fine; errors with lone pairs on Cl.
(c)(i) Challenging: particles are molecules held by weak forces, not atoms/ions/electrons.
(c)(ii) High m.p. of SiO2 due to strong covalent bonds in a giant structure; many mixed collision ideas or said “double covalent, not giant”.
Many did not read that Zn was in excess and H2SO4 was limiting.
(a)(i) Best answers: rate decreased due to lower acid concentration or collision frequency (per unit volume). ‘Less acid’ without frequency not creditworthy.
(a)(ii) One of the hardest: many claimed Zn was used up.
(b) Powdered Zn > surface area explained with particle/collision theory; many omitted “particles/frequency” or gave other misconceptions. Moderate
(c) Stoichiometry & units caused major errors (cm3?dm3, 25.0/2.00, divided by 2 etc.); random numbers without working seen.
(d)(i) Many wrote ZnCl; other errors: H as product, H written as H or 2H, wrong acid, Zn as Zn2. Moderate
(d)(ii) Test for H2: lit splint ? squeaky pop needed; confusion with O2 common. Moderate
(a)(i) Definitions vague; best: electrolyte is an ionic compound (molten/aqueous).
(a)(ii) Roman numeral = oxidation number; many wrote “means 2” / valency.
(a)(iii) Poorly answered observation — many wrote “turned blue/brown” only.
(a)(iv) Half-equations often wrong (electron placement/sign). Must describe change correctly, not “Cu2+ ? Cu – 2e?”.
(a)(v) Ion from hydroxide is OH?; many gave O2?, SO42?, word equations or compounds.
(b) Many gave valid cathode/anode observations; some swapped electrodes or described size/coating changes wrongly. Moderate
(c)(i) Challenging: electrode positions; “molten silver/insoluble salts” errors; some wrote as if Cu question.
(c)(ii) Well answered: improved appearance of spoon; wrong: “spoon is good conductor”. Moderate
(d)(i) Air pollutants: CO2 ? increased global warming; many vague or off-syllabus.
(d)(ii) Hardest: sensible disadvantage of H2 fuel cells — storage at high pressure, infrastructure, etc. (flammability/efficiency answers not accepted).
(a)(i) Generally fine, but some illogical sources of N2. Moderate
(a)(ii) Acceptable fuels: methane/natural gas only — many suggested H2/ammonia/water/air. Difficult
(a)(iii) Many mixed up Haber vs Contact conditions or gave 900 °C & 7 atm (for NO). Difficult
(a)(iv) Simple recall of catalyst poorly known; V2O5 common wrong. Moderate
(a)(v) Catalysts increase rate but are not “used up” — some wording inaccurate. Moderate
(b)(i) Very challenging: explain why given T/P not used or what happens if changed; confusion rate vs equilibrium shift. Difficult
(b)(ii) Balancing generally OK but many messy re-writes lost clarity. Moderate
(c)(i) Formula of copper(II) nitrate unknown to most; nitrate charge/acids mixed up. Difficult
(c)(ii) Evidence that acid was in excess: bubbling stops/solid stops dissolving; many repeated stem or said “reaction stops”. Difficult
(c)(iii) Expected: CuO or Cu(OH)2; many gave CuSO4. Moderate
(a)(i) Mostly correct: UV/sunlight required; some wrote only T/P. Moderate
(a)(ii) Many could draw displayed isomer(s) but some omitted bonds or duplicated mirror images as new isomers. Moderate
(b)(i) Homologous series definition weak: need same functional group plus trends/gradual changes; “similar properties” too vague. Difficult
(b)(ii) Addition polymer drawings: no C=C in repeat; show continuation bonds; monomers from alkenes only. Difficult
(c)(i) Monomers for condensation polymer: many copied polymer/omitted bonds/connected groups wrongly or drew displayed instead of molecular formulae. Difficult
(c)(ii) Many skipped; some gave examples (PET/Terylene) instead of polymer type; ‘ester/nylon’ common wrong. Difficult
(c)(iii) Even with wrong (c)(i), many could name one correct homologous series (e.g., dicarboxylic acid/diol). Moderate
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