2020 SAJC H2 Prelim Paper 2 (QP)

1 [Turn over ST ANDREW’S JUNIOR COLLEGE JC2 Preliminary Examinations Higher 2 CANDIDATE NAME CLASS 1 9 S CHEMISTRY Paper 2 Structured Questions Candidate answer on the Question Paper. Additional Materials: Data Booklet 9729/02 2 September 2020 2 hours READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen. You may use a HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. This document consists of 25 printed pages. For Examiner’s Use Q1 15 Q2 9 Q3 15 Q4 19 Q5 17 Total 75

2 [Turn over Answer all questions in the spaces provided. 1 (a) (i) On the axis below, sketch a graph to show the eleven ionisation energies for sodium. Explain the following features shown in your graph  the general trend in ionisation energy  significant change in values between ionisation energies ionisation energy …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… [3] 1 2 3 4 5 6 7 8 9 10 11 number of electrons removed

3 [Turn over (ii) State one similarity and one difference (other than difference in energy) between the lowest and highest energy occupied orbital in sodium. Similarity Difference [1] (b) (i) State two factors that affect the behaviour of beams of positively charged particles in an electric field. …………………………………………………………………………………………… …………………………………………………………………………………………… [1] (ii) On the diagram below, show how a beam of particles containing sodium ions, copper atoms and electrons deflects as they pass through an electric field at the same speed. Label your answer clearly. [2] + - beam of particles

4 [Turn over (c) Sodium and tert-butanol reacts to give sodium tert-butoxide and hydrogen gas. (CH3)3COH(l) + Na(s) (CH3)3CONa(s) + ½H2(g) ∆Hr tert-butanol sodium tert-butoxide (i) Complete the energy cycle below to calculate the enthalpy change of this reaction, ∆Hr. Your cycle should include relevant data from the Data Booklet. ∆Hr (CH3)3COH(l) + Na(s) (CH3)3CONa(s) + ½ H2(g) +141 kJ mol−1 −780 kJ mol−1 (CH3)3COH(g) + Na(g) (CH3)3CO−(g) + Na+(g) + ½ H2(g) +51 kJ mol−1 (CH3)3CO−(g) + H+(g) + Na(g) [3]

5 [Turn over (ii) The standard enthalpy change of vapourisation of butanol, tert-butanol and butanone are given below compound ∆Hvapo/ kJ mol−1 CH3CH2CH2CH2OH +46 (CH3)3COH +44 CH3CH2COCH3 +32 By considering the type of interactions involved, suggest reasons for the  difference in ∆Hvapo between tert-butanol and butanone, and  similarity in ∆Hvapo between butanol and tert-butanol. …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… …………………………………………………………………………………………… [3]

6 [Turn over (d) Compound A is a constitutional isomer of tert -butanol, (CH3)3COH. A exhibits stereoisomerism. It reacts with chlorine in the presence of UV light to form a mono - chlorinated compound B, which has four stereoisomers. Draw the four stereoisomers of B. [2] [Total: 15]

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8 [Turn over 2 (a) Explain why benzene prefers to undergo substitution reactions rather than addition reactions. ……………….………………………………………………………………………………… ……………….………………………………………………………………………………… ……………….………………………………………………………………………………… [1] (b) The reaction of phenylamine with nitrosonium ion, NO+, produces benzenediazonium ion, which is a very useful intermediate in the synthesis of many aromatic compounds. The mechanism is shown in Fig. 2.1. Fig. 2.1 (i) The electrophile, nitrosonium ion, is formed from the reaction between nitrite, NO 2−, and acid, H+. Write an ionic equation for this reaction. …………………………………………………………………………………………... [1]

9 [Turn over (ii) By considering the bonds formed and broken, show the movement of electron pairs using curly arrows for steps 1 and 3 on Fig. 2.1. [2] (iii) Using appropriate data from the Data Booklet, estimate the bond energy of the π bond in N=N. [1] (iv) Given that the bond energy of the π bond in N=O is +405 kJ mol−1, use your answer in (iii) and relevant data from the Data Booklet to calculate the enthalpy change of reaction for step 2. Hence, by considering the effect on the equilibrium, suggest whether a high or low temperature would favour the proton transfer in step 2. …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... [2]

10 [Turn over (c) Benzenediazonium ion reacts with water to form phenol readily. (i) Deduce whether water is acting as an electrophile or nucleophile in the reaction. Explain your answer. …………………………………………………………………………………………... …………………………………………………………………………………………... …………………………………………………………………………………………... [1] (ii) The reaction of benzenediazonium ion with KI(aq) forms phenol and another carbon- containing side product. Name this carbon-containing side product. …………………………………………………………………………………………... [1] [Total: 9]