2019 RVHS Prelim P2 QP

River Valley High School 9729/02/PRELIM/19 [Turn over 2019 Preliminary Examination RIVER VALLEY HIGH SCHOOL JC 2 PRELIMINARY EXAMINATION CANDIDATE NAME CLASS 18J CENTRE NUMBER S INDEX NUMBER H2 CHEMISTRY 9729/02 Paper 2 Structured Questions 18 September 2019 2 hours Candidates answer on the Question Paper. Additional Materials: 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. Answer all questions in the space provided. A Data Booklet is provided. Do NOT write anything on it. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Paper 2 Question Number 1 2 3 4 5 6 7 Total (Paper 2) sf Units Marks 9 9 10 12 12 10 13 75 Paper 1 30 Paper 3 80 Total 185 This document consists of 21 printed pages and 3 blank pages.

2 River Valley High School 9729/02/PRELIM/19 2019 Preliminary Examination 1 Group 2 metals are also known as alkaline earth metals. The elements have similar properties and appearance. The metals are silvery-white and are reactive at room temperature and pressure. (a) Ionisation energy of Group 2 varies down the group. Explain how the 1st ionisation energy of beryllium and barium differs. .………………………………………………………………………………..... .………………………………………………………………………………..... .………………………………………………………………………………..... .………………………………………………………………………………..... .………………………………………………………………………………..... .………………………………………………………………………………..... [3] (b) The nitrates, carbonates and hydroxides of Group 2 elements can undergo thermal decomposition. (i) In the thermal decomposition of Group 2 nitrates, oxygen and a brown gas are also produced. Write a balanced equation, with state symbols, for the decomposition of calcium nitrate. …………………………………………………………………………… [1] (ii) The nitrates of lead and zinc can undergo thermal decomposition similar to calcium nitrate. The decomposition temperatures of the three nitrates are given in the following table Table 1.1 Compound Decomposition temperature /C Lead(II) nitrate, Pb(NO3)2 290 Calcium nitrate, Ca(NO3)2 132 Zinc nitrate, Zn(NO3)2 105

3 River Valley High School 9729/02/PRELIM/19 [Turn over 2019 Preliminary Examination Explain, with reference to the Data Booklet, the trend in the decomposition temperatures of the metal nitrates in the Table 1.1. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. [3] (c) Lead can exhibit variable oxidation state s and its cation can exist either as 207Pb2+ or 207Pb4+. Given that the angle of deflection for 207Pb2+ is 8, calculate the angle of deflection for 207Pb4+ and draw a labelled line to the fig ure below to represent the path of a beam of 207Pb4+ ions, at high temperature, in an electric field. [2] [Total: 9]  + Beam of 207Pb4+ ions

4 River Valley High School 9729/02/PRELIM/19 2019 Preliminary Examination 2 Citric acid (H 3C6H5O7) is a naturally occuring weak organic tribasic acid. It is found in a variety of vegetables and fruits. In a typical sample of lemon, the concentration of citric acid is about 0.300 mol dm3. Table 2.1 Ka1 Ka2 Ka3 H3C6H5O7 1.43  103 1.74  105 3.98  107 (a) Calculate the pH of a typical sample of lemon. You may ignore Ka2 and Ka3 for this calculation. [1] (b) Calculated the pH of solution containing 46.0 g dm–3 of Na3C6H5O7. [3] (c) (i) A buffer solution can resist changes in pH when small amounts of acid or base is added to it. Suggest two conditions necessary to make a good buffer solution. ……………………………………………………………………………. ……………………………………………………………………………. ……………………………………………………………………………. ……………………………………………………………………………. [2]

5 River Valley High School 9729/02/PRELIM/19 [Turn over 2019 Preliminary Examination (ii) Calculate the mass of NaOH(s) required to be added to 50 cm 3 of 0.300 mol dm-3 citric acid for the preparation of buffer at pH = 6.40. Clearly identify the acid and salt species in the buffer. [3] [Total: 9] 3 Olives are commonly used in foods and production of edible oils. In their natural state, olives contain organic compounds like tyrosol that make them unpalatable to people. tyrosol In order for olives to be made edible, their natural bitterness has to be removed in a process known as debittering. This is done by soaking olives in brine, followed by sodium hydroxide solution, which will re act with tyrosol and extracted. (a) (i) Write an equation for the reaction between tyrosol and sodium hydroxide. .......................................................................................................... [1]

6 River Valley High School 9729/02/PRELIM/19 2019 Preliminary Examination (ii) State the different types of interaction that the product in (a)(i) will have with water molecules. .......................................................................................................... .......................................................................................................... [2] (iii) After treatment, tyrosol can be converted back to its original form. Outline a simple chemical test that could be carried out to check for the presence of tyrosol. .......................................................................................................... .......................................................................................................... [2] (iv) For this debittering process to be effective, the sodium hydroxide solution has to be changed frequently. Suggest, using ideas behind Le Chatelier’s principle, why the sodium hydroxide solution has to changed in order to remove tyrosol. You may find it useful to use the equation [T] olive ⇌ [T]NaOH where [T] refers to the concentration of tyrosol. .......................................................................................................... .......................................................................................................... .......................................................................................................... .......................................................................................................... [2]

7 River Valley High School 9729/02/PRELIM/19 [Turn over 2019 Preliminary Examination (b) (i) When tyrosol is heated with ethanoic acid with concentrated H2SO4, compound D is formed. When bromine water is added to tyrosol, a brominated tyrosol, E, is formed. Suggest a structure for compound D and E. D E [2] (ii) Explain how the acidity of brominated tyrosol might differ from that of tyrosol. .......................................................................................................... .......................................................................................................... .......................................................................................................... ...........................................................................................