Mock chem paper 2

IDK Junior College CANDIDATE NAME CHEMISTRY 9476/02 2 hours Additional Material(s): Data Booklet READ THE FOLLOWING FIRST Write in dark blue or black ink. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions in the spaces provided. You are reminded that there is extra working space on pages 15 & 16. Do write the question number and part clearly. The use of a scientific calculator is expected, where appropriate. You are reminded of the need for good English and legible handwriting. The number of marks is given in brackets [ ] at the end of each question or part question. For examiner’s use 1 /11 2 /15 3 /13 4 /12 5 /16 6 /8 Deductions sf: structures: units: Total /75 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. [2] ……………………………………………………………………………………………………………… (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] .………………………………………………………………………………………………………………. ..……………………………………………………………………………………………………………… (d) Given that the 1st pKa of squaric acid is 1.5, draw the predominant species present at pH 3 [1] 2

(e) You are given squaric acid, ethanoic acid and ethanol at equal concentrations. Describe their relative acidities and explain. [3] ……………………………………………………………………………………………………………….. .………………………………………………………………………………………………………………. ..……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………….. .………………………………………………………………………………………………………………. ..……………………………………………………………………………………………………………… ……………………………………………………………………………………………………………….. .………………………………………………………………………………………………………………. (f) A notable derivative of squaric acid is dibutyl squarate. (Fig. 1.3) In order to form C-O-C (ether) bonds,