2021 RVHS Prelim Paper 2 (Solutions)

River Valley High School 9729/02/PRELIMS/21 2021 Preliminary Examination Suggested Answers [Turn over RIVER VALLEY HIGH SCHOOL JC 2 PRELIMINARY EXAMINATION CANDIDATE NAME Suggested Answers CLASS 2 0 J CENTRE NUMBER S INDEX NUMBER H2 CHEMISTRY 9729/02 Paper 2 Structured Questions 15 September 2021 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 pages 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 7 Marks 12 9 12 9 8 18 7 significant figures units Total 75 This document consists of 23 printed pages and 1 blank page.

2 River Valley High School 9729/02/PRELIMS/02 2021 Preliminary Examination Suggested Answers 1 In recent years, there has been worldwide interest in the possible extraction of “shale gas” (a form of natural gas) as an important energy source. (a) One of the problems associated with using shale gas is its variable composition. Table 1 .1 shows the percentage composition of shale gas from four different sources J, K, L and M. Table 1.1 source CH4 C2Hx C3Hy CO2 N2 J 80.3 8.1 2.3 1.4 7.9 K 82.1 14.0 3.5 0.1 0.3 L 88.0 0.8 0.7 10.4 0.1 M 77.5 4.0 0.9 3.3 14.3 In the formulae above, x and y are variables. (i) Draw the structures of three possible hydrocarbons w ith 3 carbon atoms. (Any 3 of the compounds below)  CH3CH2CH3  CH3CH=CH2  CH3C≡CH  CH2=C=CH2  Δ (cyclopropane) [3] (ii) State the source of shale gas, J, K, L or M, that will likely provide the most energy when completely burned. Explain your answer. K, since it has the greatest % of hydrocarbons / carbon -containing compounds [1] (iii) Suggest a method by which carbon dioxide can be removed from shale gas. (Any one of these 3 answers)  reacted with lime / CaO / soda lime / Ca(OH)2 / KOH / NaOH /  liquefied under pressure  dissolved in water under pressure [1]

3 River Valley High School 9729/02/PRELIMS/02 2021 Preliminary Examination Suggested Answers [Turn over (b) Fracking is the process of drilling down into the earth before a high-pressure water mixture is directed at the rock to release the shale gas inside. Water, sand and chemicals are injected into the rock at high pressure which allows the