2019 HCIS IB2 HL Prelim Paper 2

− 1 − Turn over PRELIMINARY EXAMINATION International Baccalaureate 2 Chemistry Higher level Paper 2 Tuesday 3 September 2019 2 hour 15 minutes Candidate name Candidate session number Class Instructions to candidates  Write your candidate name and session number in the boxes above.  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]. 23 pages © Hwa Chong International School 2019 For Examiner’s Use Q1 /15 Q2 / 15 Q3 / 9 Q4 / 10 Q5 / 15 Q6 / 9 Q7 / 17 Total / 90

− 2 − Answer all questions. Write your answers in the boxes provided. 1. 9.74 tonnes of magnesium is needed to react with 1.60 x 10 2 tonnes of impure titanium (IV) oxide, TiO2, ore. All the titanium is completely extracted from the sample of impure ore. The following are reactions involved in the extraction process: Step 1: TiO2 + C + 2Cl2  TiCl4 + CO2 Step 2: TiCl4 + 2Mg  Ti + 2MgCl2 (1 tonne = 106 g) (a) Write an overall equation for extraction of titanium from TiO2. [1] …………………………………………………………………………………………………………………..… (b) Calculate the amount, in moles, of TiO2 present in the sample of impure ore. [1] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (c) Calculate the mass, in tonnes, of TiO2 in the sample of impure ore. [2] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (d) Calculate the percentage by mass of TiO2 in the sample. [1] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (This question continues on the following page)

− 3 − Turn over (Question 1 continued) (e) (i) Titanium (IV) oxide , TiO 2, is a solid, however titanium (IV) chloride , TiC l4, is a liquid at room temperature. Suggest a reason for this difference between the two compounds, in terms of structure and bonding. [2] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (ii) Titanium (IV) chloride is relatively stable in aqueous solutions. However, it dissolves in concentrated hydrochloric acid to form an acidic solution of the hexachlorotitanate (IV) complex ion. Draw the structure of the complex ion, suggest its molecular geometry and bond angle. [2] Geometry: ……………………………………………………………………………………………………. Bond angle: ……………………………………………………………………………………………………. (This question continues on the following page)

− 4 − (Question 1 continued) (f) Titanium exists in three important oxidation states, +2, +3 and +4. However, zinc exhibits only +2 oxidation state. (i) Write the full electron configurations of Ti2+ and Zn2+ ions. [2] Ti2+: ……………………………………………………………………………………………………………… Zn2+: …...………………………………………………………………….……………………………………… (ii) Suggest why titanium has variable oxidation states. [1] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (g) Magnesium is a s‒block element. (i) Define what is meant by ‘s’. [1] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (This question continues on the following page)

− 5 − Turn over (Question 1 continued) (ii) Sketch on the axes below, the first six ionisation energies (IE), in logarithmic scale, of the element, magnesium. [1] (iii) Explain one salient feature of the graph. [1] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. log IE No. of electron removed 1 2 3 4 5 6

− 6 − 2. Chlorofluorocarbons, CFCs, have been used previously for a wide range of applications including cleaning solvents and refrigerant. However, they break down easily in the stratosphere that lead to ozone (O3) depletion. (a) The following equations illustrate the process of ozone depletion. CCl2F2 ●CClF2 + Cl●  (1) Cl● + O3  ClO● + O2  (2) ClO● + O●  Cl● + O2  (3) (i) Identify the type of processes shown in the three equations by completing the table below: Process Equation(s) initiation propagation termination [2] (ii) Cl in equation (1) is the reactive species in this process. State the name of such species and explain its reactivity. [1] ………………………………………………………………………………………………………………….. (b) The hydroflurocarbon, F 3CCFH2, is a suitable replacement for CFCs . It is prepared industrially by reacting hydrogen fluoride with Cl2C=CClH. HCl is the by–product. (i) State the IUPAC name of F3CCFH2. [1] ………………………………………………………………………………………………………………. (ii) Construct a balanced overall equation for this reaction. [1] ………………………………………………………………………………………………………………. (This question continues on the following page)

− 7 − Turn over (Question 2 continued) (iii) Explain how HF can act as a nucleophile in this reaction. [1] ………………………………………………………………………………………………………………. (iv) Draw an isomer of F3CCFH2 that can be produced from this reaction. [1] (c) The breakdown of ozone, O3 is shown in this equation: O3 (g)  O (g) + O2 (g) H = +107.5 kJ mol–1 (i) Use relevant data from section 11 of the data booklet to determine the bond energy between oxygen atoms in ozone. [1] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. (ii) Compare the value in (i) and that in the O 2 molecule. Deduce the relative bond strengths in O2 and O3. [2] ………………………………………………………………………………………………………………. (This question continues on the following page)

− 8 − (Question 2 continued) (d) Ozone O3, can be represented in a cyclic or bent structure as shown below. Cyclic structure Bent structure (i) Determine the hybridization of the oxygen atoms in the two structures. [1] Cyclic structure: …………………………………… Bent structure: ………………………………..…… (ii) Calculate and indicate within the boxes, the formal charges of all the oxygen atoms on both structures. [2] ………………………………………………………… ………………………………………………………… ………………………………………………………… ……………………………………………………… ……………………………………………………… ……………………………………………………… (e) Hence, based on your answers from (c) and (d), suggest which of the two is the most probable structure of ozone. [2] ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………….

− 9 − Turn over 3. The following equation shows the molar coefficients of the dynamic equilibrium betwe