(i) nucleophilic substitution / $\mathrm{S_N2}$ ✔

(ii) curly arrow from the lone pair / negative charge on O of $\ce{HO-}$ to the carbon atom bonded to iodine ✔

curly arrow from the C–I bond to the I atom ✔

transition state showing the negative charge AND partial «dotted» bonds from O to C and from C to I «in square brackets, with HO and I on opposite sides of the carbon» ✔

(iii) primary halogenoalkane «little steric hindrance; a primary carbocation would be too unstable for $\mathrm{S_N1}$» ✔

(iv) 2 / second «order» ✔

(v) chloroethane / bromoethane AND the C–Cl / C–Br bond is stronger / harder to break «than C–I»

OR

chloroethane / bromoethane AND $\ce{Cl-}$ / $\ce{Br-}$ is a poorer leaving group ✔

(vi) triplet / 3 «peaks, because the neighbouring $\ce{CH2}$ group has two protons» ✔

(vii) ethanol AND presence of a broad O–H absorption in the 3200–3600 «cm⁻¹» range

OR

ethanol AND presence of a C–O absorption in the 1050–1410 «cm⁻¹» range

OR

ethanol AND absence of a C–I absorption in the 490–620 «cm⁻¹» range ✔

(i) [1]; accept SN2, do not accept SN1. (ii) M1: curly arrow from the lone pair or charge of the nucleophile to carbon; M2: curly arrow from the C–I bond to iodine, in iodoethane or in the transition state; M3: transition state with a negative charge and both partial bonds. Award [2 max] for a correct SN1 mechanism if SN1 was not stated in (i). Do not award M3 if a full HO–C bond is drawn while the C–I bond is still present. (iii) [1]; accept a reason such as lack of steric hindrance or the instability of a primary carbocation. (iv) [1]. (v) [1] for the halogenoethane with a bond-strength or leaving-group reason. (vi) [1]. (vii) [1] for ethanol with one piece of evidence; accept a specific wavenumber within the quoted ranges.