ACSI 2019 Y6 Prelim Paper 3 QP

1 Anglo-Chinese School (Independent) YEAR 6 PRELIMINARY EXAMINATION 2019 INTERNATIONAL BACCALAUREATE DIPLOMA PROGRAMME CHEMISTRY HIGHER LEVEL PAPER 3 Friday 20th September 2019 1 hour 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. • Answer all questions from Section A and Section B 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. • The maximum mark for this examination paper is 45 marks. 0 0 2 3 2 9 For examiner’s use Section A Qn 1 /8 Qn 2 /7 Section B Qn 3 /8 Qn 4 /6 Qn 5 /8 Qn 6 /4 Qn 7 /4 Total /45 Candidate Session Number ________________________________________________________________________ This question paper consists of 12 printed pages including this cover page.

2 Section A Answer all questions. Write your answers in the boxes provided. 1. The educational chart below illustrates the acid-base behaviour of element oxides based on the Pauling electronegativity and oxidation state of the element. Source: “acid-base behaviour of 100 element oxides: Visual and mathematical representations”, Journal of Chemical Education It provides a periodic trend method and a mathematical method to better understand the acid-base behaviour of oxides. The two lines, ABB1 and ABB2, are the lower and upper acid-base behaviour boundaries that are drawn to separate the chart into three areas of basic, amphoteric and acidic oxides and can be mathematically expressed with a set of equations. The bottom line (ABB1) separates the basic oxides from the amphoteric oxides and has the following equation: w1 = −3.8x + 7.93. The top line (ABB2) separates the amphoteric oxides from the acidic oxides and has the following equation: w2 = −3.8x + 12.21. General acid-base behaviour can be calculated for any oxide using the formula: ABB= 3.8x + w where ABB = Acid-base behaviour x = Pauling electronegativity w = oxidation state of element in the oxide The lower boundary line is denoted as ABB1 = 7.93 and the upper boundary line is denoted as ABB2 = 12.21. The calculated ABB value is compared with the ABB1 and ABB2 values corresponding to the boundaries to predict the acid-base behaviour. ABB1 line w1 = −3.8x + 7.93 ABB2 line w2 = −3.8x + 12.21 Oxidation state / w 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 Pauling electronegativity / x

3 (This question continues on the following page.) (Question 1 continued) Type of oxide ABB < ABB1 basic ABB1 < ABB < ABB2 amphoteric ABB > ABB2 acidic Table 1 below shows some examples of the oxides from s-, p-, d-, and f-elements with their ABB Values. s-block Name of element ABB value d-block Name of element ABB value Li2O Lithium 4.80 Sc2O3 Scandium 8.32 Na2O Sodium 4.42 VO2 Vanadium 10.08 Cs2O Caesium 4.04 NiO Nickel 9.22 MgO Magnesium 6.94 CdO Cadmium 8.46 BaO Barium 5.42 Y2O3 Yttrium 7.56 p-block Name of element ABB value f-block Name of element ABB value Al2O3 Aluminium 9.08 La2O3 Lanthanum 7.18 CO2 Carbon 13.88 Ac2O3 Actinium 7.18 SiO2 Silicon 11.22 CeO2 Cerium 8.26 P4O6 Phosphorus 11.36 PrO2 Praseodymium 8.29 SO2 Sulfur 13.88 Nd2O3 Neodymium 7.33 Table 1 (a) Using the formula given and information from section 8 of the data booklet, calculate the ABB values of As2O3 and As2O5. [2] ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ...................................................................................................................................

4 (This question continues on the following page.) (Question 1 continued) (b) Hence, predict the acid-base behaviour of As2O3 and As2O5. [2] ................................................................................................................................... ................................................................................................................................... (c) Refer to the ABB value in Table 1, suggest a chemical test, with the help of a relevant equation, which can determine the acid-base behaviour of Cs2O. [2] ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (d) What is the advantage of using this educational chart in predicting the acid-base behaviour of element oxide? [1] ................................................................................................................................... ................................................................................................................................... (e) By referring to the element oxides from p block given in table 1, state one reason to justify why the effective applicability of the chart is not 100%. [1] ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ...................................................................................................................................

5 2. A student was asked to determine the concentration of sodium hypochlorite, NaClO, in a commercially available bleach. Hypochlorite is converted to chloride ions in the presence of an acid and aqueous potassium iodide, producing brown- coloured iodine molecules. The student decided to carry out titrimetric analysis according to the steps below. Step 1: Pipette 25.0 cm3 of bleach into a 250 cm3 volumetric flask and make up to the mark with distilled water. Shake well to obtain a homogenous solution. Label the solution FA 1. Step 2: Pipette 25.0 cm3 of FA 1 into a conical flask. Add 10 cm3 of excess aqueous potassium iodide and 10 cm3 of 1.0 mol dm–3 sulfuric acid to the flask. Label the solution mixture as FA 2. Step 3: Fill the burette with 19.78 g dm–3 of sodium thiosulfate, Na2S2O3. Add about 1 cm3 of starch indicator into FA 2 and titrate until a colour change is observed. Record the results. Step 4: Repeat steps 2 to 3 as many times as necessary to obtain consistent titration results to within ±0.10 cm3. (a) Write an ionic equation for the reaction between aqueous sodium hypochlorite, dilute sulfuric acid and an excess of aqueous potassium iodide. [1] .........