2021 VJC H3 Chemistry Prelims QP

 VJC 2021 9813/01/PRELIM/21 [Turn over CANDIDATE NAME CT GROUP VICTORIA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION Higher 3 ……………………………………………….………….. …………………………….. CHEMISTRY 9813/01 Paper 1 27 September 2021 2 hours 30 minutes Candidates answer on the Question Paper. Additional Materials: Data Booklet Insert READ THESE INSTRUCTIONS FIRST Write your name and CT group on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. If additional space is required, you should use the pages at the end of this booklet. The question number must be clearly shown. Section A Answer all questions. Section B Answer two questions. A Data Booklet is provided. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question or part question. You are reminded of the need for clear presentation in your ans This document consists of 46 printed pages and 0 blank page.

© VJC 2021 9813/01/PRELIM/21 2 Section A Answer all questions in this section. The information provid ed in the insert is taken from published scientific article s. Other published articles may not agree with all of this information. You should read all the above information before you start to answer any questions and use the information it contains to answer the questions. 1 (a) (i) State two main assumptions of an ideal gas. [2] (ii) A 2 dm 3 container half filled with water was left exposed to an atmosphere of hydrogen for a long time at 0 .8 atm and 25 ºC. The resultant solution contained 6.96 × 10–4 mol dm–3 of dissolved H2 according to the following equilibrium. H2(g) ⇌ H2(aq) The atmosphere in contact with this water is replaced with 1.0 atm argon and sealed. The mixture is stirred for the gas–aqueous equilibrium to be established at 25 ºC. The hydrogen dissolved in water before the replacement is distributed between the gas phase and water after the replacement. Use equation 1.1 and the ideal gas equation to calculate the partial pressure of H2 (in atm) in the sealed container. [3] (iii) Explain how your answer in (a)(ii) will change if the temperature was increased to 50 ºC and all other conditions remained constant. [2] …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...…………………………………………………………..

© VJC 2021 9813/01/PRELIM/21 [Turn over 3 …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...…………………………………………………………..

© VJC 2021 9813/01/PRELIM/21 4 (b) (i) State and explain, using the change in oxidation numbers, the r eaction TCE underwent with H2. [1] (ii) A sample of ground water contaminated with TCE was analysed. Three other chlorine-containing organic compounds were present in the sample. Suggest the structures of these compounds. [2] …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. (c) (i) Suggest why the bubble stripping process is continued for 30 min. [1] . (ii) To determine the concentration of H2 (in ppm) in the headspace using gas chromatography, a calibration curve must first be prepared. The area count (obtained from the gas chromatogram) was measured for various known concentrations of H2 (in ppm). The data was plotted to obtain a calibration curve (Fig. 1.2). (1 ppm of H2 = 1 molecule of H2 in 106 air molecules)

© VJC 2021 9813/01/PRELIM/21 [Turn over 5 Fig. 1.2 Calibration Curve of H2 Another sample of ground water was allowed to undergo the bubble stripping process. The gas in the headspace was analysed using gas chromatography. The gas obtained has an area count of 10.4. Calculate the partial pressure of H 2 (in atm) in the headspace, stating any assumptions made during the calculation. [3] (iii) Hence, use equation 1.2 to calculate the solubility of H 2 in ground water (expressed in mole fraction), SH2, and comment on the likelihood of anaerobic biodegradation taking place in this sample of groundwater. (density of water under these conditions = 0.998 g cm–3) [3] …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...………………………………………………………….. …………………………...…………………………………………………………..

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