RVHS 2023 JC2 H2 CM Prelim P2 QP

River Valley High School 9729/02/PRELIM/23 [Turn over 2023 Preliminary Examination RIVER VALLEY HIGH SCHOOL JC 2 PRELIMINARY EXAMINATION CANDIDATE NAME CLASS 2 2 J CENTRE NUMBER S INDEX NUMBER H2 CHEMISTRY 9729/02 Paper 2 Structured Questions 13 September 2023 2 hours Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your Centre number, index number, class and name on all the work that you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions in the spaces provided on the Question Paper. If additional space is required, you should use the page at the end of this booklet. The question number must be clearly shown. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use Question Number 1 2 3 4 5 6 Marks 12 12 13 7 13 18 significant figures units Total 75 This document consists of 24 printed pages.

2 River Valley High School 9729/02/PRELIM/23 2023 Preliminary Examination 1 (a) Over one million tonnes of chromium are produced in the world each year and about 30% of it is used in electroplating. In an electroplating experiment, as shown by the set up below, an aqueous solution containing chromium( III) sulfate was electrolysed using a piece of pure chromium and the metal object to be electroplated as the electrodes. (i) Identify the anode in this reaction. ……………………..…………………………………………………........ [1] (ii) A square piece of chromium sheet has a dimension of 0.100 m  0.100 m and a depth of 1000 atoms. Assume that each chromium atom occupies a length of 3.00  1012 m, calculate how long it will take for 90.0 % of the chromium sheet to be used when a constant current of 4.00 A is provided. [3] key Chromium(III) sulfate aqueous solution Chromium sheet Power source

3 River Valley High School 9729/02/PRELIM/23 [Turn over 2023 Preliminary Examination (iii) The experiment was repeated using dilute sulfuric acid and a piece of pure aluminium in place of chromium sheet. Explain why the aluminium electrode gained mass. W rite relevant equations to support your answer. …………………………..……………………………………………........ ……………………………..………………………………………………. ………………………..……………………………………………………. ………………………..……………………………………………………. [2] (b) The s uccessive ionisation energies , in kJ mol 1, of an element X are given below. 1012, 1907, 2914, 4964, 6274, 21267, 25431, 29872 (i) With the aid of an equation involving X, explain the term first ionisation energy. …………………………..……………………………………………........ …………………………..……………………………………………........ …………………………..……………………………………………........ [1] (ii) Explain the general increase in successive ionisation energies of any atom. …………………………..……………………………………………........ …………………………..……………………………………………........ …………………………..……………………………………………........ …………………………..……………………………………………........ [2] (iii) Deduce which group of the Periodic Table X belongs to. …………………………..……………………………………………........ ……………………………..……………………………………………… …………………………..……………………………………………....... [2] (iv) Hence, write the electronic configuration of X, given that X is in Period 3. …………………………..……………………………………………........ [1] [Total: 13]

4 River Valley High School 9729/02/PRELIM/23 2023 Preliminary Examination

5 River Valley High School 9729/02/PRELIM/23 [Turn over 2023 Preliminary Examination 2 (a) Methylamine is a weak base with a p Kb value of 3.38 at 298 K. It reacts with water and boron trifluoride in acid-base reactions. CH3NH2 + H2O  CH3NH3 + + OH CH3NH2 + BF3  CH3NH2BF3 (i) State the type of base that methylamine is acting as in each reaction. Explain your answer. With H 2O: ………………………………………………………………..... ……………………………………………………………………………… ……………………………………………………………………………… With BF3: ………………………………………………………………….. ……………………………………………………………………………… ……………………………………………………………………………… [2] (ii) Calculate the pH of 0.10 mol dm3 of methylamine in water at 298 K. [2]

6 River Valley High School 9729/02/PRELIM/23 2023 Preliminary Examination (b) A buffer solution can be made from methylamine and its salt, methylammonium chloride. A suitable reagent of concentration 0.10 mol dm 3 is added to 50 cm 3 of 0.10 mol dm3 methylamine to obtain the buffer solution. (i) Name a suitable reagent that reacts with methylamine to form the buffer solution. ……………………………………………………………………………… [1] (ii) Show that the ratio of the salt to base concentration needed to maintain the buffer at pH 11.1 is 0.33. [1] (iii) Hence, calculate the volume, in cm3, of the suitable reagent to be added to form a buffer with a pH of 11.1. Leave your answer to 1 decimal place. [2]

7 River Valley High School 9729/02/PRELIM/23 [Turn over 2023 Preliminary Examination (c) FA 1 and FA 2 are either MgCO 3 or BaCO 3. The following tests were carried out to establish their identities. Test 1: When FA 1 was heated to 500 C, a gas was produced. Test 2: FA 2 produced the same gas only when heated to 1000 C. Test 3: The residues produced in tests 1 and 2 wer e then added to water separately. The residue obtained from test 1 formed a solution of pH 8 while the residue obtained from test 2 formed a solution of pH 14. With reference to the observations in Test 1 and Test 2, deduce the identities of FA 1 and FA 2. Describe the reactions of residues with water in Test 3. Write balanced equations for any reactions that occurred. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. ……………………………………………………………………………………. [4] [Total: 12]

8 River Valley High School 9729/02/PRELIM/23 2023 Preliminary Examination 3 (a) 1,3dibromopropane is the starting compound for a 4 step reaction pathway which produces compound H. The pathway is shown below. Compound F has a molecular formula of C3H4O2. Compound F gives a black precipitate when heated with [Ag(NH3)2]+(aq). (i) State the IUPAC name of compound H. …………………………………………………………………………….. [1] (ii) State the reagents and conditions for reactions 1, 2 and 3. Reaction Reagents and conditions 1 2 3 [3] (iii) Give the structures of E, F and G. Compound Structure E F G [3]

9 River Valley High School 9729/02/PRELIM/23 [Turn over 2023 Preliminary Examination (iv) 1,3-dibromopropane reacts with hot ethanolic KOH to give a compound J that has a molar mass of 40.0 g mol1. Use a suitable diagram, showing relevant orbitals, to show that the H atoms in compound J are not in the same plane. [1] (v) Compound J can isomerise into compound K which has three carbon atoms in different chemical environments. Give the structure of compound K. [1]

10 River Valley High School 9729/02/PRELIM/23 2023 Preliminary Examination (b) In contrast to compound H, lysine, an amino acid, is a naturally occuring molecule. lysine (i) Amino acids can exist as zwitterions.