2021 SAJC Prelim P2 Answer

ST ANDREW’S JUNIOR COLLEGE JC2 Preliminary Examinations Higher 2 CANDIDATE NAME CLASS 2 0 S CHEMISTRY Paper 2 Structured Questions Candidate answer on the Question Paper. Additional Materials: Data Booklet 9729/02 1 September 2021 2 hours 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 a 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 __ printed pages. For Examiner’s Use Q1 9 Q2 9 Q3 24 Q4 20 Q5 13 Total 75

Answer all questions in the spaces provided. 1 (a) Fig. 1.1 shows a sketch of the logarithm of the first ten ionisation energies, log (IE), of element A against the number of electrons removed. Fig. 1.1 (i) Write an equation for the second ionisation energy of element A. [1] A+(g)  A2+(g) + e– Must have state symbols (ii) Explain the following features of Fig. 1.1.  the general trend in ionisation energy shown in the graph  the significant jump in values from the 5th to the 6th ionisation energy [4] Ionisation energies increased as more electrons were removed. The nuclear charge remained the same , but it attracted a decreasing number of electrons . This led to an increase in the attractive forces on the remaining electrons and hence more energy was required to remove the next electron. OR Successive IE increases as remaining electrons will be attracted more strongly to increasingly positively charged ion and hence more energy was required to remove the next electron The 6th electron is from the inner quantum shell. The decrease in distance of this electron (6th electron) from the nucleus , and less shielding resulted in a 0 1 2 3 4 5 6 7 8 9 10 11 log (IE) Number of electrons removed

stronger attraction to nucleus , significant increase in the energy required to remove this electron /more difficult to remove this inner shell electron. (iii) Element A is in Period 3. Identify element A using information from Fig. 1.1 and complete it s electronic configuration. [1] Element A is phosphorus / P. 1s2 2s2 2p6 3s2 3p3 (b) Sulfur is another element in Period 3. It forms covalent bonds with other elements in covalent compounds such as SO2, SO3, SCl2. (i) Describe a covalent bond. [1] A covalent bond is the electrostatic attraction between a shared / bonding pair of electrons and two positively charged nuclei. (ii) Predict the intermolecular force which exists between SO3 molec