OCR GCE A LEVEL Chemistry A H432/03: Unified chemistry

OCR GCE A LEVEL Chemistry A H432/03: Unified chemistry. Structure and bonding NH3 is (simple) molecular/simple covalent/ /has intermolecular forces AND NH4NO3 is ionic  Comparison of strength Ionic bonds are stronger than intermolecular bonds / forces between molecules OR Ionic bonds need more energy to break than intermolecular bonds  2 AO1.1 ×2 For intermolecular bonds/forces ALLOW hydrogen bonds OR London Forces/induced dipole forces/permanent dipole forces OR van der Waals’ forces ALLOW NH4NO3 has molecular ions NH4 + and NO3 – are molecular ions ORA ALLOW: Intermolecular bonds are weak AND ionic bonds are strong  (ii) (NH4 + ) nitrogen has oxidation number of –3 AND (NO3 – ) nitrogen has oxidation number of +5  i.e. nitrogens are –3 AND +5 gets the mark BOTH signs essential 1 AO1.2 Statement that one student is correct is NOT required. Implicit in answer ALLOW 3– AND 5+ H432/03 Mark Scheme June 2022 11 H432/03 Question Answer Marks AO element Guidance (b) (i) Cu: 66% AND Zn 34%  1 AO2.6 Mark SchemeJune 2022 12 (ii) FIRST CHECK ANSWER ON THE ANSWER LINE If answer = 65.42 (to 2 DP) award 2 marks -------------------------------------------------------------------------------- Numerator from Zn isotopes (64 × 16.82) + (66 × 9.53) + (67 × 1.38) + (68 × 6.27) OR 2224.28  Relative atomic mass Numerator ÷ 34 AND answer to 2 DP  Mark ECF from numerator  = 65.42 (to 2 DP)  2 AO1.2 ×2 Refer to answer to 1b(i) for ECF from incorrect % composition of Zn and Cu ECF ÷ by Zn % in b(i) ---------------------------------------------------- Common errors 22.24 ÷100 and answer to 2 DP → 1 mark for numerator 64.23 All 6 isotopes used → No marks 188.91 All 6 isotopes used → 6423 for numerator ÷34 and 2 DP → 1 mark by ECF H432/03 Mark Scheme June 2022 13 Question Answer Marks AO element Guidance (c) (i) Proton environment Splitting pattern 1 Triplet Triplet AND 2 Quartet quartet  3 Doublet Doublet AND 4 Triplet triplet  2 AO1.2 ×2 For quartet, ALLOW Quad…. e.g. quadruplet, quadlet, quadret, etc For doublet, ALLOW duplet ALLOW diagrams to show splitting pattern e.g. for triplet for quartet ALLOW splitting patterns shown as numbers i.e. ‘3’ for triplet, ‘4’ for quartet Mark SchemeJune 2022 14 (c) (ii) Environment 2: (Protons) adjacent to (one) C=O  Environment 3: (Protons) adjacent/between/surrounded by 2 C=O / a ketone AND aldehyde OR C=O on both sides  2 AO3.1 ×2 ALLOW HC–C=O DO NOT ALLOW H–C=O DO NOT ALLOW HC–O Simply reading δ = 3.6 ppm from data sheet) IGNORE ‘next to 2 Os’ H432/03 Question Answer Marks AO element Guidance H432/03 Mark Scheme June 2022 15 (d) (i) Bond angles H2NCH2COONa, bond angle = 107º AND HOOCCH2NH3Cl, bond angle = 109.5º  Number of electron pairs Mark independently of angles In NaOH/107º, (NH2 has) 3 bonded pairs / 3 bonds AND 1 lone pair  In HCl/109.5º, (NH3 + has) 4 bonded pairs / 4 bonds  3 AO1.2 ×3 ALLOW 107 ± 0.5 ALLOW 109 OR 110º ALLOW NH2 has 4 pairs, one of which is a lone pair For bonded pairs/bonds ALLOW bonded groups, atoms, elements, regions Bonded essential IGNORE electron region OR electron density IGNORE NH3 has no lone pairs IGNORE lone pairs repel more (than bonded pairs) IGNORE shapes, even if wrong ALLOW bp for bonded pair and lp for lone pair Mark SchemeJune 2022 16 (ii) Equation: 2 H2NCH2COOH + Cu(CH3COO)2 → Cu(H2NCH2COO)2 + 2 CH3COOH  3 AO2.6 ALLOW molecular formulae or mixture, e.g. 2C2H5NO2 + CuC4H6O4 → CuC4H8N2O4 + 2C2H4O2 IGNORE charges Question Answer Marks AO element Guidance H432/03 Mark Scheme June 2022 17 Structures   Ligands must shown as bidentate rings IGNORE connectivity for NH2 BUT connectivity must be to O of COO AO2.5 ×2 i.e. IGNORE wrong or missing charges in ionic compounds if formula is correct/ e.g. ALLOW Cu(CH3COO– )2, Cu+ (CH3COO– )2 ALLOW any combination of skeletal OR structural OR displayed formula as long as unambiguous IGNORE charges ALLOW arc to represent –CH2– between: H432/03 Question Answer Marks AO element Guidance