Bukit View Prelim Ans

Bukit View Secondary School PRELIM 2024 – Chemistry 4 E Pure Chemistry Mark Scheme 1 P1 Qns 1 2 3 4 5 6 7 8 9 10 Ans B D B A B C B A A C Qns 11 12 13 14 15 16 17 18 19 20 Ans B C A B C D D C B D Qns 21 22 23 24 25 26 27 28 29 30 Ans C A D B C D C C C C Qns 31 32 33 34 35 36 37 38 39 40 Ans C A A B D C C B B B MCQ analysis: 1 Qn did not mention speed of reaction or loss of mass to record volume of gas 2 Liquids – no need mp, 3 A, C and D wrong from graph 4 Solid sodium chloride is soluble, filtration is for insoluble solid 5 Bp of water 100 deg, anything above cannot be boiled to vapour 6 Mr NH 3:17, Mr N2:28, 7 1 X: 19 p 18 e 21 n 2 Y: 19 p 19 e 20 n 3 Z: 16 p 18 e 18 n 8 Since only part of the substance reacts with acid, it must be a mixture. Iron would completely react with acid, given enough time. Since the entire substance conducts electricity, it must be a mixture of metals. Brass is the best answer. 9 R+ : Q- 8 : 4 2 : 1 10 Graphite – only 3 bonds occupied, Graphene – all bonds occupied – no delocalised e, Graphene – layered structure similar to graphite – soft than diamond 11 Y from group 16 – proton numbers in group 16 12 Co: NH 3 36.6/59 : 63.4/17 1 : 6 13 Convert to mol  multiply 6.02 x 10^23 H2: 1 mol, Ne: 0.2 mol, O2:0.25 mol, CO2:0.5 mol 14 20 dm 3 H2 needs only 20 dm3 Cl2, hence 10 dm3 Cl2 excess + 40 dm3 HCl 15 Mol water = 27/18 = 1/5 mol Mol pure NH4NO3 = 0.75 mol , mass NH4NO3 = 0.75 X 80 = 60.0 g 16 80% - 60 100% -75 g calculated mass Mol urea – 75/60 = 1.25 mol, mol NH3 = 2.5 mol , mass NH3 = 42.5 g

Bukit View Secondary School PRELIM 2024 – Chemistry 4 E Pure Chemistry Mark Scheme 2 17 Max temp reached is where acid has been neutralised. Take volumes from this temp. Mol H2SO4 = 0.03 mol, mol NaOH reacted = 2 x 0.03 = 0.06 mol, conc NaOH = 3mol/dm3 18 Strong acid, completely ionise – A,B wrong, D- depends on amount of water 19 Sulfur dioxide formed dissolves in water for form acidic solution. 20 Acidic and amphoteric oxides react with bases 21 Conductance depends on mobile ions, K has high conductance, temperature change same – both neutralise sodium hydroxide, K reacts rapidly with Mg 22 Zn + Cu(NO3)2  Zn(NO3)2 + Cu [displacement], B,C & D no reactions 23 White ppt with aq ammonia soluble – Zinc Blue ppt forming dark blue sol with aq ammonia – Cu 2+ 24 Cl (0) in Cl 2 to Cl (-1) in NaCl and Cl (+1) in NaOCl 25 A: H + and Cl- discharged, NaOH – more alkaline B: Cu2+ and OH- discharged , H2SO4 – more acidic C: Cu2+ discharged and released from electrode – no change D : H+ and OH- discharged, becomes more conc NaCl 26 Need mobile ions/ electrons/ more & less reactive metals connected 27 Zn 2+ + 2e  Zn (s) 1 mol 0.5 mol Crx+ + xe  Cr (s) 1mol 0.2 mol 1/0.2 = 5 28 Most reactive: U, V, Fe, W Least reactive 29 P>Q 30 Charge from group no., acidic / bas