2013_TPJC_H1_Chemistry_P2 Suggested Solution

TPJC_2013_8872_02 [Turn over TAMPINES JUNIOR COLLEGE JC2 Preliminary Examination CANDIDATE NAME TUTOR NAME 1 2 CHEMISTRY Paper 2 Candidates answer Section A on the Question Paper. Additional Materials: Answer Paper Data Booklet 8872/02 Thursday, 05 September 2013 2 hours H1 CIVICS GROUP For Examiner’s Use Section A B5 B6 B7 Total READ THESE INSTRUCTIONS FIRST Write your name and civics group on all the work you hand in. Write in dark blue or black pen. You may use a pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all the questions. Section B Answer two questions on separate answer paper. 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 18 printed pages.

2 Section A Answer all questions in this section in the spaces provided. For Examiner’s Use 1 Radiotherapy is the medical use of radiation generated from radioactive isotopes to destroy or weaken malfunctioning cells. Examples of radioactive isotopes used for the therapy are those of iodine, phosphorus and lutetium. (a) Lutetium has two naturally occurring isotopes, 175Lu and 176Lu. Their natural abundances are 97.4% and 2.6% respectively. (i) Define the term relative atomic mass. Relative atomic mass is defined as the ratio of the average mass of one atom of an element to 12 1 the mass of an atom of 12C isotope, expressed on the 12C scale. [1] (ii) Calculate, to one decimal place, the relative atomic mass of lutetium. Ar of Lu = 0.175100 1766.21754.97 =×+× [1] [2] (b) 176Lu has a half-life of 101078.3 × years. The half-life of a radioactive isotope is the time taken for half of the atoms in a given mass to decay. Calculate the percentage of a sample of 176Lu isotopes remaining after 1110134.1 × years. number of half-lives = 31078.3 10134.1 10 11 =× × % of sample remaining = % 5.122 1100 3 =⎟ ⎠ ⎞⎜ ⎝ ⎛× [2] [2] Iodine-131 is used to treat the thyroid for cancers and phosphorus-32 is used to control the excess of red blood cells produced in the bone marrow. (c) Complete the table below for the 131I and 32P isotopes. Isotope Number of protons Number of neutrons 131I 53 78 [1] 32P 15 17 [1]

3 Radioactive isotopes are commonly incorporated into compounds to trace the path of biochemical reactions. These compounds are known as radioactive tracers. The structure of fluorodeoxyglucose (18F-FDG), a radioactive tracer widely used in medical imaging, is shown below. O OH OH F18 OH OH 18F-FDG (d) (i) Apart from ether (–O–), circle and name the functional groups that are present in the 18F-FDG shown above. O OH OH