ACJC_H2_CHEM_P2_Ans Prelim

1 © ACJC 2017 9729/02/Prelim/2017 [Turn over Index No. Name Form Class Tutorial Class Subject Tutor ANGLO-CHINESE JUNIOR COLLEGE DEPARTMENT OF CHEMISTRY Preliminary Examination CHEMISTRY 9729/02 Higher 2 Paper 2 Structured Questions 15 August 2017 2 hours Candidates answer on the Question Paper Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, index number, form class, tutorial class and subject tutor’s name on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, glue or correction fluid. Answer all questions. A Data Booklet is provided. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together. For Examiner's Use Question no. Marks 1 / 7 2 / 13 3 / 9 4 / 11 5 / 5 6 / 9 7 / 14 8 / 7 TOTAL / 75 This document consists of 21 printed pages, including this cover page. 9729/02/Prelim/17 ANGLO-CHINESE JUNIOR COLLEGE © ACJC 2017 Department of Chemistry [Turn over

2 © ACJC 2017 9729/02/Prelim/2017 [Turn over For more than two millenia human ingenuity has turned natural and synthetic poisons into weapons of war. World War I was especially hailed by historians as the “Chemists’ War” because it was the first war in which chemical weapons were used on such an enormous scale, even on civilians. Chemicals were used to bring widespread destruction and death. It set the precedence for World War II. On the bright side, chemicals were used to save millions of soldiers’ lives in World War II. Question 1 examines how chemical weapons were used to kill in World War I, while Question 2 examines the use of chemicals as medicine in the battlefields of World War II. 1 A range of different chemicals - chlorine, phosgene and mustard “gas” - were used as weapons throughout World War I. Their melting and boiling points are tabulated below. Gas Melting point / 0C Boiling point / 0C chlorine -101.5 -34.0 phosgene -118 8.3 mustard “gas” 14.4 217.0 Chlorine was first used on a large scale by the German forces at Ypres in April 1915. It reacts with water in the lungs to form hydrochloric acid, which can quickly lead to death. At lower concentrations, it can cause coughing, vomiting, and irritation to the eyes. (a) Phosgene is a colourless gas, with an odour likened to that of ‘musty hay’. O C ClCl phosgene Phosgene is known to react violently with water to give hydrochloric acid and carbonic acid. Give the equation of the reaction betw