2025 H1 Chem 8873 Prelim P2 QP_CJC

CANDIDATE NAME CLASS 2T CHEMISTRY 8873/02 Paper 2 Structured Questions 29 August 2025 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet 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 an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Section A Answer all the questions. Section B Answer one question. The use of an approved scientific calculator is expected where appropriate. You are reminded of the need for good English and clear presentation in your answers. A Data Booklet is provided. The number of marks is given in brackets [ ] at the end of each question or part of the question. This document consists of 25 printed pages and 1 blank page Section A Q1 5 Q2 6 Q3 15 Q4 16 Q5 6 Q6 12 Section B Q7 20 Q8 20 Paper 2 (67%) 80 Paper 1 (33%) 30 Percentage Grade Catholic Junior College JC2 Preliminary Examinations Higher 1

2 8873/02/CJC JC2 Preliminary Examinations 2025 Section A Answer all the questions in this section in the spaces provided. 1(a) The hydrogen carbonate ion, HCO3‒, has both acidic and basic properties. State the conjugate acid and conjugate base of HCO3‒. Conjugate acid: ................................ ................................ ................................ ............. Conjugate base: ................................ ................................ ................................ ........ [1] (b) In the human body, it is important for blood to be maintained at a pH between 7.35 and 7.45. The main buffering agent in blood plasma is the H2CO3(aq) / HCO3–(aq) system. During a vigorous physical workout, the muscles will produce an acid which will be transported by the blood to the liver to be broken down. (i) Define the term buffer solution. ................................ ................................ ................................ .............................. ................................ ................................ ................................ .......................... [1] (ii) Briefly explain the effect physical workout will have on the pH of blood if there is no buffer present. ................................ ................................ ................................ .............................. ................................ ................................ ................................ .............................. ................................ ................................ ................................ .............................. ................................ ................................ ................................ .......................... [2] (iii) Write an equation to explain how the H2CO3(aq) /