Organic compounds can be distinguished using chemical tests. Table 4.1 shows four pairs of compounds. [Table 4.1 showing pairs A1/A2, B1/B2, C1/C2, D1/D2 with structures]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2022). The mark or mark type is shown in brackets.

1. [2] For A1 (ketone) / A2 (primary alcohol): Reagent: K2Cr2O7 OR KMnO4 OR Na; Positive result: A2 make solution turn (orange to) green OR turn colourless OR effervescence (respectively)
2. [2] For B1 (methyl ketone) / B2 (ester): Reagent: alkaline I2(aq)/ OR 2,4-DNPH; Positive result: B1 gives yellow/orange ppt OR B1 gives red/yellow/orange ppt (respectively)
3. [2] For C1 (alkane) / C2 (alkene): Reagent: Br2(aq); Positive result: C2 turns it (orange to) colourless
4. [2] For D1 (diol) / D2 (carboxylic acid): Reagent: Na2CO3 / NaHCO3; Positive result: D2 gives effervescence
5. [1] M1 (m.& b.pts are low because) weak intermolecular forces / weak van der Waals
6. [1] M2 (only) London / dispersion forces / instantaneous dipole-induced dipole
7. [1] {cis-pent-2-ene structure}
8. [1] addition
9. [1] correct carbon backbone including 'dangling' bonds for ONE repeat unit
10. [1] rest of structure correct