2017 RVHS H2 Chemistry P3 Qns

River Valley High School 9729/03/PRELIM II/17 [Turn over 2017 Preliminary Examination II RIVER VALLEY HIGH SCHOOL YEAR 6 PRELIMINARY EXAMINATION II CANDIDATE NAME CLASS 6 CENTRE NUMBER S INDEX NUMBER H2 CHEMISTRY 9729/03 Paper 3 Free Response 19 September 2017 2 hours Candidates answer on separate paper. Additional Materials: Answer Paper Cover Page Data Booklet READ THESE INSTRUCTIONS FIRST Write your name, class, centre number and index number on all the work you hand in. Write in dark blue or black pen on both sides of paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all questions. Section B Answer one question. Begin each question on a fresh sheet of paper. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. Do not write anything on it. You are reminded of the need for good English and clear presentation in your answers. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together, with the cover page on top. This document consists of 14 printed pages and 2 blank pages.

2 River Valley High School 9729/03/PRELIM II/17 2017 Preliminary Examination II Section A Answer all the questions in this section. 1 (a) Under suitable conditions, SCl2 reacts with water to produce a yellow solid and an acidic solution A. Solution A contains a mixture of SO 2(aq) and another compound. (i) State the oxidation number of S in SCl2 . [1] (ii) Construct an equation for the reaction between SCl2 and water. [1] (iii) In the Contact Process, one important step is the conversion of SO2 to SO3 as shown below. 2SO2(g) + O2(g) ⇌ 2SO3(g) A 2.00 L flask was filled with 0.0400 mol SO 2 and 0.0200 mol O 2. At equilibrium, the flask contained 0.0296 mol of SO3. Determine the value of Kc, stating its unit. [3] (b) During the electrolysis of dilute sulfuric acid using a current of 0.75 A for 90 min and platinum electrodes, the volume of oxygen gas collected wa s recorded and is shown in Table 1.1 below. Table 1.1 Time / min Volume of O2 gas / cm3 20 55 40 110 60 165 80 220 (i) Plot a graph of volume of O2 gas over time. Use x axis: 2 cm for 10 min ; y axis: 2 cm for 50 cm3 [2] (ii) Give equations for the reactions that occur at each electrode in the electrolysis of sulfuric acid. [2] (iii) On the same graph, draw and label a line (H2) to predict the volume of hydrogen that would be given off during the same experiment. [1] (iv) On the same graph, draw and label a line (O2) to predict the volume of oxygen that would be given off if a current of 0.3 A was used instead in the original experiment. [1]

3 River Valley High School 9729/03/PRELIM II/17 [Turn over 2017 Preliminary Examination II (v) In a second experiment, the platinum electrodes were replaced with graphite electrodes. The volume of gas collected at the anode was 150 cm 3 while the volume of hydrogen gas collected was 220 cm3. The difference in volume of gas collected at the anode between the two experiments was due to the production of CO gas at the anode. Calculate the volume of CO gas produced at the anode. [2] (c) About 100 years ago, in a reaction discovered by German chemist Karl Fries, compound B was converted into compound C when heated with AlCl3. Compound C is a structural isomer of B. It is insoluble in water but dissolves in aqueous sodium hydroxide. It give s a yellow ppt with alkaline aqueous iodine and a white ppt with aqueous bromine. (i) Suggest the structure for compound C. [1] The various reactions of compound C can be represented as follows: (ii) Suggest the structures for D to G. [4]

4 River Valley High School 9729/03/PRELIM II/17 2017 Preliminary Examination II Compound H, as shown below, is another structural isomer of B. It has a ether functional group whose general formula is RO−R’. Compound H can be formed via a reaction between a substituted phenoxide ion and an alkyl halide molecule. (iii) Describe the mechanism when compound H is formed as described above. [3] [Total: 21]

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6 River Valley High School 9729/03/PRELIM II/17 2017 Preliminary Examination II 2 In the late 1940s, Willard Libby developed the radiocarbon dating method for determining the age of an object containing organic material by using the properties of radiocarbon (14C), a radioactive isotope of carbon. The principle of carbon dating is as such: During its life, a plant or animal is exchanging carbon with its surroundings, so the carbon it contains will have the same proportion of 14C as the atmosphere. Once it dies, it ceases to acquire 14C, but the 14C within its biological material at that time will continue to decay, and so the ratio of 14C to 12C in its remains will gradually decrease. Because 14C decays with first order kinetics , the proportion of radiocarbon can be used to determine how long it has been since a given sample stopped exchanging carbon – the older the sample, the less 14C will be left. (a) A sample of carbon dioxide gas (that contained both 12CO2 and 14CO2) was analysed to determine the proportion of 14CO2 found within. Analysis results showed that there is one 14CO2 molecule for every 1012 CO2 molecules. (i) Calculate the number of 14CO2 molecules in a 10.0 dm 3 carbon dioxide gas sample, measured under s.t.p. [2] (ii) Calculate the mass of 14CO2 in the 10.0 dm3 sample. [1] (iii) Hence, explain why it would be difficult to determine the proportion of 14CO2 by means of mass measurement. [1] (b) To more accurately determine the proportion of 14C in a sample of graphite, the graphite is vaporised and ionised to C +(g) ions. These ions were then passed through 2 electric plates. Given that H + is deflected with an angle of 8.4°, what is the angle of deflection for 14C+ ions under the same experimental set-up? [1] (c) The half-life of 14C is 5730 years. Determine the time that has elapsed for a piece of wood from a dead tree to contain 30.0% of its original 14C. [2]

7 River Valley High School 9729/03/PRELIM II/17 [Turn over 2017 Preliminary Examination II (d) The age of crude oil is far older than what could be determined from radiocarbon dating. To measure the age of a crude oil sample, a method involving the measurement of the relative amount of oleanane is used instead. Oleanane (i) What is the number of chiral carbons in an oleanane molecule? [1] (ii) Free radical substitution of oleanane with Cl2 produces a mixture of various products. Given that tertiary hydrogen atoms are the most reactive towards free radical substitution, suggest the structures of two possible mono-chlorinated oleanane which are formed in high proportions. [2]

8 River Valley High School 9729/03/PRELIM II/17 2017 Preliminary Examination II (e) Benzene is obtained from the fractional distillation of crude oil. It can be converted to a series of different useful chemicals such as phenylamine. The formation of phenylamine involves the direct reaction of nitrobenzen e and hydrogen gas in the presence of a heterogeneous catalyst. A series of experiments were carried out at a specific temperature to investigate the kinetics of this reaction: Experiment [nitrobenzene] / mol dm–3 [H2] / mol dm–3 Initial rate / mol dm–3 s–1 1 0.010 0.010 4.50 × 10–5 2 0.015 0.010 6.74 × 10–5 3 0.020 0.020 1.80 × 10–4 4 0.030 x 4.05 × 10–4 (i) Define the term heterogeneous catalyst. [2] (i