Overall standard was very high. As this was the first June exam after a syllabus update, some candidates were unfamiliar with newer content.
Care with subscripts in formulae and correct upper/lower case is needed. When only one answer is asked for, giving more can contradict correct statements and lose credit.
Choices from eight metal oxides. (a),(b),(d) usually correct; (c) and (f) more difficult; (e) hardest (many assumed iron(III) oxide is the main impurity of iron ore).
(a) Group VII correctly named as halogens; ‘halide’ common error.
(b) Many omitted the word ‘number’; some used outdated term ‘valence shell electrons’.
(c) States/colours of halogens new to syllabus; weaker candidates confused bromine with bromine water (orange).
(d) (i) Nucleon/mass number poorly known. (ii) Strong candidates scored full marks; occasional confusion in the neutron row. (iii) Isotopic mass × abundance required; final rounding to 80/80.0 from 79.9 seen.
(e) (i) KCl formation known but equation errors (e.g. Br not Br2). (ii) Most realised reaction did not occur (Cl2 less reactive than F2).
(f) (i) White precipitate formation known; some described effervescence. (ii) Symbol instead of ionic equations common; spectator ions often left in.
(a) Contact process widely known; a few wrote Haber.
(b)(i) New content LO 6.3.9 caused difficulty (burning sulfur vs roasting sulfide ores). (ii) Equilibrium wording needed care; best: “concentrations of products and reactants stay the same”.
(b)(iii) Temperature and catalyst identity known; correct pressure in kPa less so (e.g. “2 kPa” error); vanadium oxidation state often wrong.
(b)(iv) Most predicted effects of changing conditions. (v) Explanations via collision theory often incomplete; few referenced particles having energy > Ea; some wrongly said Ea changes.
(c) Very challenging multi-step oxidation-number method; many omitted sign on oxidation number; ions quoted instead of oxidation numbers.
(a) Base = proton acceptor; (b) soluble base = alkali; (c) colour of thymolphthalein in alkali known.
(d) Products of word equation known; occasional ‘ammonium’ for ammonia and ‘hydrogen’ for water.
(e)(i) Poorly answered (‘acidic’ common); best responses gave ‘amphoteric’. (ii) Many still named a correct amphoteric oxide.
(f)(i) Dot-and-cross for ethanoic acid: many omitted lone pairs on both O atoms or used same symbols; some only drew single bonds or a dot-cross double bond.
(g) (i) pH must be in valid range (not 7 for a strong acid). (ii) Reversible arrows required; (iii) many wrote single H+ or 4H+ instead of CH3COO? formation; (iv) recall of new LO 7.1.8 was mixed.
NB: Fractions as final answers and leaving Mr as a sum (e.g. 2+32+64) may not receive full credit.
(a)(i)(iii) Mostly correct; substitution and photochemical mentioned often; (iv) some wrote ‘disubstitution’ against wording.
(b)(i) Explanations too vague; must reference C–C bonds (saying “there is a C=C” is insufficient). (ii) Better candidates wrote 1,2-dichloropropane; many gave 1,3-/1,1- isomers or ambiguous C3H6Cl2.
(c) Propan-2-ol often correct, but “propanol”/propan-1-ol confusion common; many omitted the O–H in displayed formula; IUPAC naming beyond two carbons caused issues.
(a) Name of ester known; common misspelling “butanote” for butanoate.
(b) Water as a product of esterification well known, though some wrote other products.
(c) Many stated molecular formula instead of simplifying to empirical formula.
(d)(i) Circling a repeat unit from an end helped; circling the ester link only or a middle unit was weaker. (ii) Many didn’t show discrete monomers or mis-connected O–H creating “divalent H” or transposed groups. (iii) Most recognised condensation polymerisation.
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