2023 EJC H3 Chemistry Prelim Key Answer

© EJC [Turn Over EUNOIA JUNIOR COLLEGE JC2 Preliminary Examination 2023 General Certificate of Education Advanced Level Higher 3 CANDIDATE NAME CIVICS GROUP 2 2 – INDEX NUMBER CHEMISTRY Paper 1 9813/01 22 September 2023 2 hours 30 minutes Candidates answer on Question Paper. Additional Materials: Data Booklet Insert READ THESE INSTRUCTIONS FIRST Write your name, civics group and registration number on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staplers, paper clips, 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. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. 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 Section A 1 / 20 2 / 11 3 / 16 4 / 13 Section B 5 / 20 6 / 20 7 / 20 Total / 100 This document consists of 48 printed pages.

2 © EJC 9813/01/J2PE/23 Section A Answer all the questions in this section. 1 (a) Carbon dioxide is the primary but not the sole contributor to the carbon reserve in the atmosphere. (i) Name another greenhouse gas which contributes to the carbon reserve and state one source of this gas. [2] (ii) Assume that the carbon reserve in the atmosphere is fully in the form of CO 2, and that the composition of dry air by volume is 78.08% N 2, 20.95% O 2, 0.93% Ar and 0.04% CO 2. Use the data in Fig. 1.1 to estimate the mass of the Earth’s atmosphere, in kg. [2] ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ (i) Methane Any one:  roduced by domestic livestock as part of their normal digestive process.  roduced during the storage and management of animal manure  roduction, processing, storage, transmission, distribution, and use of natural gas  roduction, refinement, transportation, and storage of crude oil  enerated in landfills as waste decomposes  enerated in the treatment of wastewater (ii)      78.08 20.95 0.93 0.04mass of 1 mol of air 28.0 32.0 39.9 44.0100 100 100 100

3 © EJC 9813/01/J2PE/23 [Turn Over (b) (i) State the main way CO2 is captured by the soil sink. [1] (ii) What is the main cause for the rapid increase in concentration of CO 2 since 1750, which also resulted in a decrease in the Earth’s carbon reserve? [1] (iii) Assuming that the anthropogenic CO 2 emission remains the same as that in 2022 shown in Fig. 1.1, use your answer to (a)(ii) to calculate the expected concentration of CO2, in ppm, by the end of 2023. Use a value of 4.15 ൈ 1016 kg for the mass of the Earth’s atmosphere if you are not able to calculate one in (a)(ii). [3] ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ ................................................................................................................................ (i) Through photosynthesis where CO 2 is converted into carbohydrates in plants and trees. (ii) Burning of fossil fuels for energy generation. (iii) 46.4mass of C added to the atmosphere in one year 11.2 5.20 GtC100   12 3 2 14 5.20 10 10amount of CO per