ACSI 2022 Promo Paper 2_Questions_

1 Anglo-Chinese School (Independent) YEAR 5 Promotional Examination 2022 INTERNATIONAL BACCALAUREATE DIPLOMA PROGRAMME CHEMISTRY HIGHER LEVEL PAPER 2 Monday 12th September 2022 2 hours 15 minutes INSTRUCTIONS TO CANDIDATES • Do not open this examination paper until instructed to do so. • Write your candidate session number in the box above. • A calculator is required for this paper. • A copy of the Chemistry Data Booklet is required for this paper. • Write your answers in the boxes provided. • If you use additional sheets of paper for your answer, attach them to the booklet. Indicate the question number clearly on these sheets. • All drawings must be in ink. For examiner’s use Qn 1 /10 Qn 2 /6 Qn 3 /11 Qn 4 /5 Qn 5 /13 Qn 6 /8 Qn 7 /17 Qn 8 /11 Qn 9 /9 Wrong s.f. /units Total /90 ________________________________________________________________________ This question paper consists of 26 printed pages including this cover page.

2 Answer all questions. Write your answers in the boxes provided. ...................................................................................................................................................... ...................................................................................................................................................... ...................................................................................................................................................... ...................................................................................................................................................... ...................................................................................................................................................... ...................................................................................................................................................... (This question continues on the following page) 1. Chile saltpetre is a mineral found in Chile and Peru, which mainly consists of sodium nitrate, NaNO3. The mineral is purified to concentrate the NaNO3 which is used as a fertilizer and in some fireworks. To determine the purity of a sample of NaNO3, a (1.64 ± 0.02) g impure sample was heated in NaOH (aq) with Devarda’s alloy which contains aluminium. This reduces the NaNO3 to ammonia which is boiled off and then dissolved in acid as shown in the following equation. 3NaNO3 (aq) + 8Al (s) + 5NaOH (aq) + 18H2O (l) → 3NH3 (g) + 8NaAl(OH)4 (aq) The NH3 gas produced is dissolved in (25.00 ± 0.06) cm3 of 1.00 mol dm–3 H2SO4. 2NH3 + H2SO4 → (NH4)2SO4 The resulting solution was titrated with 2.00 mol dm–3 NaOH to determine the amount of unreacted H2SO4. (16.20 ± 0.10) cm3 of NaOH were required for complete neutralization. H2SO4