Mock chem paper 2 suggested solutions (corrected)

IDK Junior College CANDIDATE NAME CHEMISTRY SOLUTIONS 9476/02 2 hours Additional Material(s): None READ THE FOLLOWING FIRST I do hope you have enjoyed/learnt something from this paper. It is meant to be a tad unconventional and unusual, do take heart in having tried your very best! For organic structures, it will be penalised on the front page under structures if bonds are not bonded to the correct atom, e.g. C–HO, C–H 2 N et cetera. This is the first paper I have ever made, so any feedback/inquiries will be greatly appreciated! Despite best attempts to ensure accuracy, some mistakes may arise and if so, do email ian321714@gmail.com. In general, answers are written in blue with their marks denoted next to them. Diagrams are in black because my software does not support other colours unfortunately :( Information written in red are deductions/potential pitfalls that you must look out for, or just general helpful tips. This document consists of 16 pages 1

Answer all questions 1 Squaric acid is a dibasic organic acid. Fig. 1.1. shows the skeletal formula of squaric acid. Fig. 1.1 (a) State the IUPAC name of this compound. You are told that priority goes to the carbonyl groups. (suffix) [2] 3,4-dihydroxycyclobut-3-en(e)-1,2-dione - 1 mark for correct numbering - 1 mark for correct name - The (e) is optional. (b) Fig. 1.2 shows the delocalisation of the divalent squarate anion. Draw, on Fig 1.2, curly arrows and lone pairs to show how this resonance stabilisation is achieved, from left to right. [1] Fig. 1.2 (c) Hence, suggest why the divalent squarate anion is a perfect square. [1] The electrons are delocalised equally across the entire molecule , and so the electron density is equally distributed, so the bond lengths of the bonds are equal , resulting in a perfect square. - 1 mark for both parts (d) Given that the 1st pKa of squaric acid is 1.5, draw the predominant species present at pH 3 [1] [1] For correct species drawn (only 1 H is deprotonated) with a negative charge 2

(e) You are given squaric acid, ethanoic acid and ethanol at equal concentrations. Describ