2022 EJC Prelims Paper 2 QP

© EJC [Turn Over EUNOIA JUNIOR COLLEGE JC2 Preliminary Examination 2022 General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CIVICS GROUP 2 1 – INDEX NUMBER CHEMISTRY Paper 2 Structured Questions 9729/02 15 September 2022 2 hours Candidates answer on the Question Paper Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, civics group, index number on all the work you hand in. Write in dark blue or black pen. You may use an 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. For Examiner’s Use Paper 2 1 / 20 2 / 20 3 / 18 4 / 17 Total / 75 This document consists of 19 printed pages and 1 blank page.

2 © EJC 9729/02/J2PE/22 For Examiner’s Use 1 The carbon family consists of the elements of Group 14. The elements at the top of the group, carbon to germanium, have very different properties from those at the bottom, tin and lead. For instance, Group 14 elements tend to adopt oxidation states of +4 , whereas the heavier elements, such as tin and lead, exhibit the +2 oxidation state due to the inert pair effect. (a) State the valence shell configuration of Group 14 elements. ................................ ................................ ................................ ................................ [1] (b) One of the contributing factors to the inert pair effect is the unexpected increase in the ionisation energies, after lead, down the group. Explain why the 1st ionisation energies are expected to decrease down the group. ................................ ................................ ................................ ................................ .... ................................ ................................ ................................ ................................ .... ................................ ................................ ................................ ................................ .... ................................ ................................ ................................ ................................ .... ................................ ................................ ................................ ................................ [2] (c) Carbon forms carbide anion, C 2– 2 in calcium carbide while silicon mostly forms Si4+ ions. (i) Draw the dot-and-cross diagram of the carbide anion, C 2– 2 . [1] (ii) In a particular experimental set-up, a beam of 28Si4+ ions was deflected by an angle of +4.2º. Assuming an identical set of conditions, by what angle will the 12C 2– 2 ions be deflected? [1]

3 © EJC 9729/02/J2PE/22 [Turn Over For Examiner’s Use (d) Table 1.1 shows that the melting points of the elements of Group 14. Table 1.1 element C Si Ge Sn Pb melting point / C >3550 1410 937 232 327 Carbon, silicon and germanium each form a solid with the same type of structure. Using bonding and structure, suggest why the melting points of these elements decrease from carbon to germanium. ................................ ................................ ................................ ................................ .... ................................ ................................ ................................ ................................ .... ................................ ................................ ................................ ................................ .... ................................ ................................ ................................ ................................ .... ................................ ................................ ................................ ................................ [2] (e) Carbon forms many allotropes such as graphite and diamond . Recent scientific research has found that replacing the graphite electrodes with graphene in lithium-ion batteries can extend battery life. (i) Graphene is a single, one atom thick layer of graphite. Describe the hybridisation of the orbitals in, and the bonds between, the carbon atoms within graphene. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ......................... [2] (ii) Using your answer from (e)(i), explain why graphene can conduct electricity along the plane. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ......................... [1]

4 © EJC 9729/02/J2PE/22 For Examiner’s Use (iii) State and explain how you would expect the bond strength of carbon-carbon bonds in graphene to differ when compared with that in diamond. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ......................... [2] (f) Diamond and graphite are allotropes of carbon. Fig. 1.1 gives the structure of diamond and graphite. Diamond is an important abrasive while graphite is used as a lubricant. Fig. 1.1 (i) Explain why the sign of the entropy change for the conversion of diamond to graphite is positive. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ............................. ................................ ................................ ................................ ......................... [2]

5 © EJC 9729/02/J2PE/22 [Turn Over For Examiner’s Use (ii) The standard enthalpy change of reaction for the conversion of diamond to graphite is exothermic. Explain whether the conversion of diamond to graphite is spontaneous at all temperature