2019 TJC H2 Chem Prelim P2 QP

1 [Turn over DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 9729 / TJC Prelim / 2019 CANDIDATE NAME CIVICS GROUP / CENTER NUMBER S INDEX NUMBER CHEMISTRY 9729/02 Paper 2 Structured Questions 28 August 2019 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your Civics Group, centre number, index number and name 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. This document consists of 20 printed pages For Examiner’s Use 1 /7 2 /10 3 /10 4 /14 5 /20 6 /14 Total / 75 PRELIMINARY EXAMINATIONS HIGHER 2

2 [Turn over DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 9729 / TJC Prelim / 2019 1 (a) The table below shows the first, second and third ionisation energies of some elements in the Periodic Table. Element First Ionisation energy (kJ mol-1) Second Ionisation energy (kJ mol-1) Third Ionisation energy (kJ mol-1) Ca 590 1150 4940 Mn 716 1510 3250 Fe 762 1560 2960 Co 757 1640 3230 Ni 736 1750 3390 (i) Explain why the first and second ionisation energies of the transition metals are relatively invariant. [2] (ii) Write the electronic configurations of Ca and Fe atoms at ground state. Explain the differences in the values of the third ionisation energies between iron and calcium. [2]

3 [Turn over DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 9729 / TJC Prelim / 2019 (b) Calcium cyanamide, CaCN2, is used as a fertiliser in agriculture. Through hydrolysis in the presence of carbon dioxide, calcium cyanamide produces cyanamide, NH2CN. Cyanamide can be extracted by organic solvents. (i) Draw the dot–and–cross diagram for the cyanamide m