Copy of KCPSS_2024_4E_Chem_Prelim_P3_MS

KUO CHUAN PRESBYTERIAN SECONDARY SCHOOL SECONDARY FOUR EXPRESS 2024 EOC CHEMISTRY PRACTICAL TEST PRELIM EXAMS MARKING RUBRIC Relative Weighting Skill Areas Total Marks Relative Weighting (%) Manipulation, measurement and observation (MMO) 5 37.5 Presentation of data and observations (PDO) 13 15.0 Analysis, conclusions and evaluation (ACE) 16 37.5 Planning (P) 6 12.5 From SEAB O Level 6092 Syllabus Document The assessment of Planning (P) will have a weighting of 15%. The assessment of skill areas MMO, PDO and ACE will have a weighting of 85%. Qn Skill Indicative Material Mark Total 1(a) (i) Titration number 1 2 3 Final burette reading / cm3 27.10 20.90 23.20 Initial burette reading / cm3 11.10 7.20 9.30 volume of P used /cm3 16.00 13.70 13.90 Best titration results (√) √ √ [5] PDO PDO PDO PDO Correct header with units Readings to the nearest 0.05 cm 3 Compare average value with teacher’s value: ±0.20 cm 3, ± 0.30 cm3 Concordance: ±0.20 cm 3 1 1 2 1 1(a) (ii) ACE average volume of P = (13.70 + 13.90) / 2 = 13.80 cm3 (with 2 dp and correct units) 1 [1] 1(b) (i) ACE No. of moles of KOH (aq) = 0.0500 x 25.00 / 1000 = 0.00125 mol 1 [1] 1(b) (ii) ACE No. of moles of malic acid in average volume of P = ½ x 0.00125 = 0.000625 mol 1 [1] 1(b) (iii) ACE Concentration (mol/dm3) of malic acid in P = 0.000625 / 0.01380 = 0.453 mol/dm3 (e.c.f. applies) 1 [1] 1(c) ACE Presence of other acids in the juice, so greater volumes of KOH needed to neutralise it. 1 [1]

Qn Skill Indicative Material Mark Total 1(d) (i) MMO Test 1: A green/blue-green flame is observed. Test 2: The green solid dissolves in nitric acid to form a blue solution. The blue solution turns green. Test 3: Upon adding water, the green solution turns back to blue. 1 1 1 1 [4] 1(d) (ii) P MMO Test 4: Add nitric acid, and add aqueous silver nitrate. observation: A white ppt. will be formed. 1 1 [2] 1(d) (iii) ACE To remove any possible carbonate ions that might be present in the sample of salt R. 1 [1] 2(a) (i) PDO 24.0; 0.0 [Note: both values correct and in correct d.p. for 1 mark] 1 [1] 2(a) (ii) PDO Correct calculation of (40/72 = 0.56) AND correct units cm3/s 1 [1] 2(b) ACE Increasing volume of dilute sulfuric acid and decreasing volume of deionised water  increase concentration of dilute sulfuric acid Resulting in decrease in time taken and thus higher rate of reaction (accept: faster reaction; relate time to rate of reaction) OR show calculation of rate of reaction for the experiments. 1 1 [2] 2(c) ACE The reaction can be started by tipping the flask, thus do not have to replace / remove the bung, so that no gas escapes / all the hydrogen gas produced can be accurately collected and measured (while the bung is removed / replaced). 1 [1] 2(d) P Apparatus (A) • Electronic balance • Conica