MARKING SCHEME CHEMISTRY PAPER SECTION A (454/) Question scheme Sub (a) A: Detergents B: Soap r : sodium salt magnesium ion // or calcium ion SKEMA SBP0 (b)(i) r : Mg +, Ca + (b)(ii) Soaps are biodegradable Total (c) (d)(i) (d)(ii) Analgesics Psychotherapeutic r: wrong spelling Sugar Aspartame To add / restore the colour of food // To enhance its visual appeal / appearance// more attractive https://cikguadura.wordpress.com/ TOTAL 9 Question (a)(i) Magnesium r:mg scheme (a)(ii) Has shell occupied with electrons (b). Proton number of chlorine is higher than magnesium // the number of proton of chlorine atom higher than magnesium atom // total positive charged in nucleus higher than magnesium. The attractive force between the nucleus and the electrons in chlorine atom stronger than magnesium atom // nuclei attraction towards electrons stronger. Sub Total (c) Light bulb // in welding process (d) Argon (e)(i) Cl (g) + Fe (s) FeCl (s) (e)(ii) Mass iron (III) chloride = 0.05 x 6 // 8.05 g
(e)(ii) Chlorine gas Gas klorin Heat Panaskan Hot iron wool Wul besi panas Total 9 Question scheme Sub (a)(i) 6 (a)(ii) To estimate the age of fossils and artifacts (a)(iii) C- // C- Total C 6 Or C 6 (a)(iv) 7 / 6 4 (b)(i) A: covalent r: covalent bond B: ionic r: ionic bond (b)(ii).8.8. (b)(iii) High melting point and boiling point // conduct electricity in molten or aqueous solution // soluble in water // insoluble in organic solvent. [Any one] (c)(iv) K + Cl KCl. Formula of reactants and products correct. Balance the chemical equation TOTAL 6 0 4
Question 4(a)(i) 4(a)(ii) 4(a)(iii) 4(b)(i) 4(b)(ii) scheme Pipette r: wrong spelling Phenolphthalein // methyl orange r: wrong spelling Phenolphthalein : pink to colourless // methyl orange : yellow to orange KOH + H SO 4 K SO 4 + H O Formula of reactants and products correct Balance the chemical equation. Mol of KOH = (.0)(5) / 000 = 0.05 mol. Molarity of H SO 4 = (0.05)(000) / 0 =.5 mol dm - // Molarity of H SO 4 = 0.05 /0.0 =.5 mol dm - Or M av M V b a b a ; Molarity of H SO 4 = b r: wrong unit or without unit (5) x 0 =.5 mol dm - Sub Total 4(c)(i) 4(c)(ii) Hydrogen ion r: H + (symbol ion). no water. contain of molecule // no hydrogen ion, H + TOTAL 0 5
Question scheme Sub Total 5(a) Chemical formula that shows the simplest whole number ratio of atom of each element in the compound. 5(b)(i) Mass of Mg =.4 g Mass of O =.6 g 5(b)(ii) Mole of Mg =.4 / 4 = 0. Mol of O =.6 / 6 = 0. Mg : O = : 5(b)(iii) MgO 5(b)(iv) to allow oxygen enter the crucible 5(b)(v) Repeat the process heating, cooling and weighing until a 6 constant mass is obtained. 5(c) crucible Magnesium ribbon Heat Apparatus set-up correct and functional Labeled : magnesium ribbon, heat 5(d)(i) Zinc oxide // aluminium oxide r: formula 5(d)(ii) Silver is less reactive / not reactive metal TOTAL 6
Question scheme Sub 6(a) Hydrogenation 6(b) C 4 H 8 + H C 4 H 0 6(c)(i) Mole of butene =.8 /56 = 0.05 mol Total 6(c)(ii) 6(d) 6(e)(i) 6(e)(ii) P. mol of butene burns in oxygen gas produce 4 mol of carbon dioxide. Therefore 0.05 mol of butene burns in oxygen gas produce 0. mol of carbon dioxide // C 4 H 8 : CO : 4 0.05 : 0. P. volume of CO = 0. x 4 = 4.8 dm P: cm of but--ene and cm of butane gas are filled in two different test tubes. P : - drops of acidified potassium manganate (VII) solution is added to both test tubes. P: But--ene decolourises purple acidified KMnO 4 Purple acidified KMnO 4 in butane remains unchange. Or P: cm of but--ene and cm of butane gas are filled in two different test tubes. P : - drops of bromine water is added to both test tubes. P: But--ene decolourises brown bromine water. Brown bromine water in butane remains unchange. A: unvulcanised rubber B: vulcanised rubber Rubber type B/ vulcanised rubber is more elastic than rubber type A/ unvulcanised rubber TOTAL Or 5 7
SECTION B Question scheme Σ 7 (a) (i) Ascending order : Cu, Y,X, W (ii) P : Positive terminal : Cu P : Potential difference :.V P: Copper is less electropositive // X is more electropositive correct value and unit 4 7 ( b) (i) Experiment I : Pb +, Cl - Experiment II: H +. OH -, Cl r: lead(ii) ion, chloride ion Hydrogen ion, hydroxide ion, chloride ion Experiment Experiment II Product at anode: Chlorine gas Products at cathode: Oxygen gas + Reason: Reason: P: Cl - is discharged P:OH - is selected to be discharged + 7(b)(ii) P: the only anion presence and discharged at anode P:the position of OH - is lower than Cl - in electrochemical series +.Half equation:. Half equation: Cl - Cl + e 4OH - H O + O + 4e P:Correct formula of reactant and product : P: Balance equation P: Correct formula of reactant and product P: Balance equation + + 0 8
7(c) P: Positive terminal: R P: Negative terminal:cu P: Suitable metal for R : Silver P4: Suitable solution for R : Silver nitate solution 4 Total 0 Question scheme Σ 8(a) P. Smaller size has larger total surface area. P. Absorb heat faster. P. Bigger size has smaller total surface area. P4. Absorb heat slower 4 (b)(i) Copper(II) sulphate (b)(ii) (b)(iii). Experiment I Rate of reaction = 40/ = 0 cm min -. Experiment II Rate of reaction = 60/ = 0 cm min - P. Rate of reaction in Experiment II is higher than Experiment I. P. Substance X used in Experiment II is a catalyst. P. Catalyst provided an alternative path with requires a lower activation energy. P4. More particles are able to achieve lower activation energy. P5. Frequency of effective collisions between zinc atoms and hydrogen ions are higher. 5 9
(b)(iv). Label of axes and unit. Correct curve and label Volume of gas / cm Exp II Exp I Time / min (v). Correct formula of reactants and product. Balanced equation Zn + H + Zn + + H (vi). Rate of reaction using sulphuric acid is higher.. Volume of hydrogen gas released is doubled.. Sulphuric acid is a diprotic acid. 4. Concentration of hydrogen ions in sulphuric acid is double than that in hydrochloric acid. 4 Total 0 0
Question scheme Σ 9(a) P: Magnesium atom undergoes oxidation P: oxidation number increases from 0 to + P: Copper (II) ion undergoes reduction P4: oxidation number decreases from + to 0 MAX P5: The reaction involving oxidation and reduction 4 (b) Experiment I L can reduce copper(ii) oxide// L can react with copper(ii) oxide L is more reactive than copper. Experiment II M can reduce copper(ii) oxide//m can react with copper(ii) oxide M is more reactive than copper. Experiment III M cannot reduce L oxide // M cannot react with L oxide. M is less reactive than L//L is more reactive than M. Max 6 5 The arrangement in order of increasing reactivity toward oxygen is Cu, M and L. (c) Procedure : P. Pour cm of potassium bromide solution into a test tube. P. Add cm of chlorine water to the test tube and shake the mixture. P. Add cm of,, trichloroethane to the test tube and shake the mixture. P4. Record the observation P5. Repeat steps -4 using another halogens and halide solution..
Result : Chlorine water Bromine water Iodine water Potassium chloride X X Potassium bromide X Potassium iodide Ionic equation:. Cl + Br - Cl - + Br. Cl + I - Cl - + I. Br + I - Br - + I 0 https://cikguadura.wordpress.com/ 0
Question scheme Σ Precipitation / double decomposition reaction 0(a) Barium nitrate solution/barium chloride solution [Any sulphate solution] Example: sodium sulphate, potasium sulphate, sulphuric acid Reject : Lead(II) sulphate, calcium sulphate Ba + + SO 4 BaSO 4 4 0(b)(i) Cation : Iron(II) ion / Fe + Anion: Chloride ion / Cl Test for NO 0(b)(ii) P: Add cm of dilute sulphuric acid into the test tube follow by cm of iron(ii) sulphate solution. P: Add a few drops of concentrated sulphuric acid P: carefully and slowly along the side of slanting test tube into the mixture. P: A brown ring is formed. 4 Procedure: 0(c) P. Add zinc nitrate solution to sodium carbonate solution in a beaker. P. Stir the mixture. P. Filter the white precipitate/solid zinc carbonate formed. P4. Add zinc carbonate to sulphuric acid in a beaker until some zinc carbonate solid no longer dissolve. P5. Filter the mixture. P6. Transfer the filtrate to a evaporating dish. P7. Heat the filtrate(zinc sulphate solution) until saturated// Heat the filtrate to about one-third (/) of its initial volume P8. Allow the saturated solution to cool at room temperature. P9. Filter the crystals formed. P0. Dry the crystals by pressing it between two sheets of filter papers. 0 Total 0
ing Scheme Chemistry Paper [KK050 Mengukur menggunakan nombor] SKEMA SBP0 (a) Able to measure the diameter of dents correctly and accurately Copper:.5,.60,.50 Bronze:.0,.00,.0 Able to measure the diameter of dents without decimal point Able to state 4 diameter of dents correctly [KK0506 Berkomunikasi] (b) Able to construct the table with correct label and unit Type of Diameter of dents(cm) Average diameter blocks I II III of dents (cm) Copper.5.60.50.48 Bronze.0.00.0. Able to construct the table without correct label or unit Able to construct the idea of table https://cikguadura.wordpress.com/ [KK050 Memerhati] (c) (i) Able to state the observation correctly and accurately The average diameter of dents on bronze block is. cm, the average diameter of dents on copper block is.48 cm.// The size / diameter of dents on bronze block is smaller than the size / diameter of dents on copper block// The size / diameter of dents on copper block is bigger than the size / diameter of dents on bronze block Able to state the incomplete observation Able to state the average diameter of one block only. The size / diameter of dents on bronze block is smaller// The size / diameter of dents on copper block is bigger. Able to state the idea of observation Sample answer : The size / diameter of dents on bronze block is small/ The size / diameter of dents on copper block is big.
[KK 0504 Membuat Inferens] (c)(ii) Able to state the inference correctly and accurately Bronze is harder than copper // Copper is less harder than bronze Able to state the incomplete inference correctly Sample answer : Bronze is harder // Copper is less harder Able to state the idea of inference Sample answer : Bronze is hard// Copper is soft [KK0508 Mentafsir data] (c)(iii) Able to explain the arrangement of particles in the materials correctly. The atomic size of tin is bigger than copper// The atomic size of tin and copper are different. The presence of tin atoms in bronze disrupts the orderly arrangement of copper atoms. Reduces/ Prevent the layers of atoms from sliding over each other/ easily. Able to state any points // points without the name of atoms correctly Able to state point point correctly [KK050 Mengawal pemboleh ubah] (d) Able to state all the variables Manipulated variable : Type of materials / blocks// Copper and bronze Responding variable : Size / diameter of dents Fixed variable : Size / diameter and mass of steel ball bearing // height of the weight // mass of the weight Able to state two variables correctly Able to state one variable correctly
[KK05 Membuat hipotesis] (e)(i) Able to state the hypothesis correctly Bronze is harder than copper // Copper is less harder than bronze Able to state the hypothesis less correctly Able to state idea of hypothesis [KK0509 Mendefinisikan secara operasi] (e)(ii) Able to state the operational definition correctly The smaller dent produced when a kg weight is dropped on the block. Able to state the operational definition less correctly The smaller dent produced when a weight is dropped on the block// When a weight is dropped on the block results smaller dent, thus the harder the block is. Able to state idea of operational definition The harder block has a smaller dent. [KK050 Mengelas] (e)(ii) Able to classify all substances correctly Alloy Pure metal Steel Iron Brass Chromium Pewter Tin Able to classify at least 4 substances less correctly Alloy Pure metal Steel Iron Brass Chromium Tin Pewter Able to state idea of classification (at least correct) Sample answer : Alloy Iron Chromium Pewter Pure metal Steel Brass Tin
[KK0505 Meramal] (a). Able to show an extrapolation on the graph. 500 Heat of combustion/ kj mol - Haba pembakaran/ kj mol - 000 500 000 500 000 500 5 0 4 Number of carbon atom per molecule of alcohols. Range of answer[ 600-700 ]. Show the negative sign and correct unit, kjmol - Able to state any two correct answers Able to state any one correct answer [KK0507 Menggunakan perhubungan ruang dan masa] (b) Able to state the relationship between the number of carbon atom per molecule and the time taken for cooking correctly Sample answer The higher the number of carbon atom per molecule alcohol, the shorter the time taken for cooking Able to state the relationship between the number of carbon atom per molecule and the time taken for cooking less correctly Sample answer The higher the number of carbon atom, the shorter the time taken for cooking Able to give relevant idea 4
[KK05 Menyatakan masalah] (a) Able to give the problem statement correctly How does different type of metals in contact with iron affect rusting?// Does more electropositive metal in contact with iron inhibit the rusting of iron?// Does less electropositive metal in contact with iron speed up the rusting of iron? Able to give the problem statement less correctly To investigate the affect of other metals on the rusting of iron// How does a metal affect the rusting of iron? Able to state an idea of hypothesis More electropositive metal inhibit the rusting of iron// Less electropositive metal speed up the rusting of iron KK05 Menyatakan pemboleh ubah] Question Rubric s (b) Able to state all the three variables correctly Manipulated variable : Name of metal R and metal S// type of metals Responding variable : Rusting of iron//iron rust//formation of blue spot Constant variables: Iron nail//gelatine solution with potassium hexacyanoferrate(iii) and phenolpthtalein Able to state any two variables correctly Able to state any one variable correctly 5
[KK05 Menulis hipotesis] Question Rubric s (c) Able to state the relationship between the manipulated variable and the responding variable and state the direction. When a more electropositive metal is in contact with iron, the metal inhibits rusting. // When a less electropositive metal is in contact with iron, the metal speed up rusting Able to state the relationship between the manipulated variable and the responding variable less correctly A more electropositive metal will prevent iron from rusting. // A less electropositive metal will cause iron to rust. Able to state an idea of hypothesis Metal R and metal S affect rusting (of iron) [KK05 Menyenaraikan bahan dan radas] Question Rubric (d) Able to give complete list of substances and apparatus Answer: Substances Two Iron nails, Magnesium/zinc/aluminium strip Tin/copper/lead/silver strip Potassium hexacyanoferrate(iii) solution + phenolphthalein [Any suitable electrolyte]/[water] Apparatus Test tube/boiling tube Test tube rack Sand paper Able to list basic materials and apparatus Materials Magnesium/zinc/aluminium strip Tin/copper/lead/silver strip Iron nail Any suitable electrolyte 6
Apparatus: Any suitable container Able to give an idea of the materials and apparatus Materials Iron Any electrolyte Apparatus Any suitable container [KK05 Memilih teknik] Question Rubric s (e) Able to state all the steps correctly. Clean the iron nails and metals strip with sand paper.. Coil iron nails with magnesium ribbon and copper strip.. Put the coiled iron nail into different test tubes. 4. Pour the hot jelly solution containing potassium hexacyanoferrate(iii)solution and phenolphthalein into the test tube. 5. Leave the test tube in a test tube rack for a day. 6. Record the observation. Able to state the steps,4,and 6 correctly Able to state steps and 4 correctly [ and 4 ]//the idea combining iron and any metals and any substances 7
[KK05 Mempamerkan perancangan] Question Rubric s (f) Able to tabulate the data with the following aspects. Heading for the manipulated variables [pair of metals//test Tube]. Heading for responding variables Pair of metals Observation Mg/Fe Cu/Fe Able to give an idea on tabulation of data at least one information stated in the table. At least one heading Sample answer Set https://cikguadura.wordpress.com/ PERATURAN PEMARKAHAN TAMAT 8