2021 ACSI Prelims Paper 2

1 Anglo-Chinese School (Independent) 6092/2 Year 4 Express Preliminary Exam 2021 [Turn over Anglo-Chinese School (Independent) Year 4 Express Preliminary Examination 2021 CHEMISTRY PAPER 2 6092/2 Tuesday 17th August 2021 1 hour 45 minutes Additional materials: Calculator INSTRUCTIONS TO CANDIDATES Write your candidate number in the box at the top of this page and on any separate answer paper used. Section A Answer all questions in the spaces provided. Section B Answer all three questions in the spaces provided. The last question is in the form of EITHER / OR and only one alternative should be attempted. At the end of the examination, hand up the paper in one bundle. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is printed on page 23. You may use a calculator. This question paper consists of 23 printed pages. Candidate Number FOR EXAMINER’S USE Section A B9 B10 B11 significant figures units TOTAL

2 Anglo-Chinese School (Independent) 6092/2 Year 4 Express Preliminary Exam 2021 [Turn over Section A Answer all questions in the spaces provided. The total mark for this section is 50. A1 The diagram shows part of the Periodic Table. Use the letters S-Z to answer the questions below. S-Z does not represent the symbols of the actual elements. Z U X T V S W Y (a) Which element exists as a solid at r.t.p, has low density and floats on water? [1] (b) Which element shows both metallic and non-metallic character? [1] (c) Which elements are transition elements? [1] (d) State two characteristic properties of transition elements. [2] (e) Which gaseous element is likely to remain as a monoatomic substance? [1]

3 Anglo-Chinese School (Independent) 6092/2 Year 4 Express Preliminary Exam 2021 [Turn over A2 The reaction between nitrogen and hydrogen to form ammonia is a reversible reaction as shown below. forward reaction : N2 (g) + 3H2 (g) → 2NH3 (g) ∆H = - 92 kJ/mol backward reaction : 2NH3 (g) → N2 (g) + 3H2 (g) ∆H = + 92 kJ/mol In order to determine the most cost-effective way to produce ammonia, a chemist Fritz Haber did a series of experiments to determine the yield of ammonia at different conditions. temperature / oC pressure / atm 300 400 500 400 48% NH3 55% NH3 61% NH3 500 26% NH3 32% NH3 38% NH3 600 13% NH3 17% NH3 21% NH3 (a) Using the information given, state the conditions needed to produce the highest yield of ammonia. [1] (b) Explain why the Haber Process is carried out at only 250 atm. [1]