2023 SOTA Yr 6 Chem HL Prelim Exam P2

Yr6/4/CHEM/HP2/Aug2023 20 pages © School of the Arts, Singapore CHEMISTRY Higher level Paper 2 Preliminary Examinations Wednesday 30 August 2023 2 hours 15 minutes INSTRUCTIONS TO CANDIDATES • Write your name, class and index number in the blanks below. • Do not open this examination paper until instructed to do so. • Answer all questions. • Answers must be written within the answer boxes provided. • A calculator is required for this paper. • A clean copy of the chemistry data booklet is required for this paper. • The maximum mark for this examination paper is [90 marks]. Name: Class: Index: 90

Yr6/4/CHEM/HP2/Aug2023 - 2 - 1. (a) An oxide of chromium contains 68.4% of chromium and 31.6% of oxygen. The mass spectrum of the oxide shows its molecular ion peak at m/z = 156. Determine the molecular formula of the oxide, showing your working. [3] ………..………………………………………………………………………………………… ………………………………………..………………………………………………………… ………..………………………………………………………………………………………… ………..………………………………………………………………………………………… ………………………………………..………………………………………………………… ………..…………………………………………………………………………………………………..………………………………………………………………………………………… ………………………………………..………………………………………………………… ………..………………………………………………………………………………………… (b) (i) When copper compounds are introduced into a gas flame, the flame turns green. Calcium compounds produce a brick red flame while chromium compounds produce a silver-white flame. Explain why different colours are observed in the gas flame. [2] ………..………………………………………………………………………………………… ………………………………………..………………………………………………………… ………..………………………………………………………………………………………… ………..………………………………………………………………………………………… ………………………………………..………………………………………………………… ………..………………………………………………………………………………………… (ii) Explain the convergence of lines in an emission spectrum. [1] ………..………………………………………………………………………………………… ………………………………………..………………………………………………………… ………..………………………………………………………………………………………… (iii) The frequency of convergence limit for the chromium atom is 1.64 × 1015 s−1. Calculate the ionization energy, in J, for a single atom of chromium using sections 1 and 2 of the data booklet. [1] ………..………………………………………………………………………………………… ………………………………………..………………………………………………………… ………..…………………………………………………………………………………………

Yr6/4/CHEM/HP2/Aug2023 Turn over - 3 - (c) (i) State the full electron configuration of the chromium atom. [1] ………..………………………………………………………………………………………… (ii) Predict and explain the magnetic properties of chromium atoms and chromium(III) ions. [2] ………..………………………………………………………………………………………… ………………………………………..………………………………………………………… ………..………………………………………………………………………………………… ………..………………………………………………………………………………………… (iii) Describe how the bonds between water ligands and chromium(I