ANSWERS CHEMISTRY PAPER 2 TRIAL

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1 ANSWERS CHEMISTRY PAPER 2 TRIAL 1.(a) i. Point S Titik S ii. R to S = Liquid R ke S = Cecair T to U = Solid T ke U = Pepejal (b) The loops in heat during the cooling process is balanced with the heat released to form new bonds between the particles of acetamide when it changes from liquid to solid. Lengkung haba semasa proses penyejukan adalah seimbang diantara haba dibebaskan untuk membentuk ikatan baru antara partikel asetamida apabila ia bertukar dari cecair ke pepejal. (c) Solid Pepejal (d) i. X = Sublimation X = Pemejalwapan Y = Condensation Y = Kondensasi ii. X = Heat is absorbed X = Haba diserap Y = Heat is liberated Y = Haba dibebaskan 2.(a) i. V ii. U iii. S (b) The melting point increases from P to R. (c) The radius of atom R is larger than that of atom Q, hence atom R has a stronger tendency to release the single valence electron to form an ion in a chemical reaction. (d) Atom T has a stable octet electron arrangement. It does not

2 need to share electrons with atom S to form a compound. (e) (f) As a catalyst in the reaction between nitrogen and hydrogen to form ammonia. 3.(a) Yellow to orange Kuning ke jingga (b) H 2 SO 4 + 2NaOH Na 2 SO 4 + 2H 2 O (c) (d) 1 mol H 2 SO 4 neutralises 2 mol NaOH 1 mol H 2 SO 4 dineutralkan 2 mol NaOH

3 (e) Asid sulfuric is a diprotic acid but acid hydrochloride is a monoprotic acid. 1 mol H 2 SO 4 ionizes to obtain 2 times of no of mol of H + in the solution compared to 1 mol of HCl. Asid sulfurik ialah asid diprotik tetapi asid hidroklorik ialah asid monoprotik. 1 mol H 2 SO 4 diionkan untuk mendapatkan 2 kali bilangan mol H + di dalam larutan berbanding 1 mol HCl. 4.(a) Contact Process Proses Sentuh (b) Sulphur dioxide Sulfur dioksida (c) S + O 2 SO 2 (d) Temperature: ºC; Catalyst: Vanadium(V) oxide Suhu: ºC; mangkin: Vanadium(V) oksida and pressure : 1 atm dan tekanan: 1 atm (e) 2SO 2 + O 2 2SO 3 (f) (i) Oleum (ii) SO 3 + H 2 SO 4 H 2 S 2 O 7

4 (g) This is because sulphur trioxide reacts too violently with water and gives out a lot of heat. A large cloud of sulphuric acid mist is also produced. Hal ini kerana sulfur trioksida bertindak balas cergas dengan air dan membebaskan banyak tenaga haba. Banyak asap dihasilkan. (h) To manufacture fertilizers/paints or pigments Untuk menghasilkan baja/cat atau pigmen 5. (a) A hydrocarbon which has a double bond between two of its carbon atoms. Hidrogen yang mempunyai ikatan ganda dua antara dua atom karbonnya. (b) Add a bit of bromine water and shake. Tambahkan sedikit air bromin dan goncangkan. Propene decolorize the brown colour of the bromine water but propane does not. Propena melunturkan warna perang air bromin tetapi propana tidak. (c) Combustion of these compounds produces carbon dioxide and water. Pembakaran sebatian ini menghasilkan karbon dioksida dan air. (d) Propene = (e) = 85.71% Propane = = 81.81% % of carbon by mass of propane is higher. % jisim karbon propana lebih tinggi.

5 (f) x = hydrogen hidrogen y = steam stim (g) C 3 H 6 + H 2 C 3 H 8 6. (a) Fe + Cu 2+ Fe 2+ + Cu (b) Heat evolved when 1 mol of a metal ion is reduced to metal by a more reactive element. (c) (i) Heat evolved = = 1470 J (ii) (iii) (d) Lower temperature change is expected. (e) Reddish brown solid is formed.

6 7. (a) A process by which a compound in the molten or aqueous state is broken down into its constituent elements [1 m] when an electric currents is passed through it. [1 m] (b) i. In solid lead(ii) chloride, lead(ii), Pb 2+ ions and bromide Br ions are not free to move. [1 m] Lead(II) bromide is heated until molten [1 m] to obtain free moving lead(ii) ions and bromide ions. [1 m] lead(ii), Pb 2+ ions are attracted to the cathode while [1 m] bromide Br ions are attracted to the anode [1 m] when the switch is on and the circuit is completed. [1 m] ii. The pointer of the ammeter deflected when the switch is on. [1 m] A grey solid is deposited at the cathode and [1 m] a brown gas is collected in syringe [1 m] In molten lead(ii) bromide, the lead(ii), Pb 2+ ions and bromide, Br ions are free to move. [2 m] The Pb 2+ ions are attracted to the anode when the carbon electrodes are dipped into the switch and the switch in on. [3 m] The Pb 2+ ions are discharged at the cathode by accepting electrons to form lead [1 m Br ions are discharged at the anode by donating electrons to form bromine gas [1 m] cathode: Pb e Pb [1 m] anode: 2Br Br + 2e [1 m] 8.(a) The usage of barbiturate to reduces worries, nervousness and depression. [1 m] Excessive use will lead to death. [1 m] (b) (i)

7 (ii) Additives in detergent: Fluorescence agent - increase brightness of the clothes. [1 m] Biological enzymes - acts on protein, animal tissue and plants, break into smaller compounds [1 m] Drying agent - to make sure that the detergent powder is always dry. [1 m] Stabiliser - stabilise the bubbles and reduce the amount of bubbles formed. [1 m] (c) Materials: Salicylic acid, ethanoic anhydride, concentrated sulphuric acid, distilled water Apparatus: Beaker, Bunsen burner, measuring cylinder, filter funnel and fi lter papers [1 m] Procedures: 1. 5 g of salicylic acid is weighed and poured into a small beaker. [1 m] 2. 7 cm 3 of ethanoic anhydride are measured using a measuring cylinder and poured into the beaker filled with salicylic acid. [1 m] 3. Two to three drops of concentrated sulphuric acid are added and the mixture is stirred. [1 m] 4. The mixture is warmed for 2-3 minutes and poured into a beaker fi lled with 100 cm 3 of distilled water. [1 m] 5. The mixture is stirred until white solid formed. [1 m] 6. White solid is filtered, rinsed with distilled water and dried with filter papers. [1m] 9.(a) i. Insoluble salt Garam tak larut [1 m] ii. Experiment I/Eksperimen I: Pb 2+ + Cl PbCl 2 [1 m] Experiment II/Eksperimen II: Pb 2+ + CrO 4 2 PbCrO 4 [1 m] iii. White Putih [1 m] iv. Filtration Penurasan [1 m] (b) i. Reaction between an acid and an alkali Tindak balas antara asid dan alkali [1 m] Reaction between an acid and metal Tindak balas antara asid dan logam [1 m] Reaction between an acid and a metal carbonate

8 Tindak bals antara asid dan logam karbonat [1 m] Reaction between an acid and a metal oxide or hydroxide Tindak balas antara asid dan metal oksida atau hidroksida [1 m] ii. Add a little of distilled water to impure salt. Masukkan sedikit air suling ke garam tak tulen. [1 m] Heated the mixture while stirring an add more distilled water until all the salts are dissolved. Panaskan campuran sambil mengacau dan tambahkan lebih banyak air suling sehingga semua garam larut. [1m+1m] Filtered the hot solution into a clean conical flask to remove impurities. Turaskan larutan panas ke dalam kelalang yang bersih untuk mengeluarkan bendasing. [1 m] The filtrate is evaporated until a saturated salt is formed. Hasil turasan mengewap sehingga garam dengan kepekatan yang tinggi. [1 m] Allow the saturated salt to cool at room temperature for crystallization. Garam tersebut disejukkan pada suhu bilik untuk pengkristalan. [1 m] The filtered salt are then rinsed with distilled water and dried between two pieces of filter paper. Garam yang telah dituras kemudiannya dibilas dengan air suling dan dikeringkan antara dua kertas turas. [1 m+1 m] 10.(a) The copper slowly dissolves and the solution turns blue. At the same time, the copper becomes coated with a layer of silver metal. Kuprum akan larut secara perlahan dan larutan akan bertukar menjadi biru. Pada masa yang sama, kuprum akan diselaputi oleh lapisan logam perak. [2m] Silver ion oxidizing agent accept electron Ion perak agen pengoksidaan terima elektron [2m] Copper reducing agent donates electrons Kuprum agen penurunan derma elektron [2m] Half reactions: Ag + + e - Ag Cu Cu e - [2m] Overall reactions: Cu + 2Ag + Cu Ag [2m] (b) Chemical: Copper (II) sulphate solution and zinc plate Bahan kimia: Larutan kuprum(ii) dan plat zink [1m] Experiment/Eksperimen:

9 Zinc plate is immersed in copper(ii) sulphate solution in a beaker Plat zink direndam dalam larutan kuprum (II) sulfat di dalam bikar [1m] The mixture is left aside for half an hour Campuran dibiarkan selama setengah jam [1m] The changes that takes place on zinc plate and copper (II) sulphate solution are recorded Perubahan yang berlaku pada plat zink dan larutan kuprum (II) sulfat direkodkan[1m] Observation/Pemerhatian: Zinc plat dissolves/plat zink melarut [1m] Brown precipitate is deposited on the zinc plate Mendakan perang termendap pada plat zink [1m] Blue solution turns colourless Larutan biru bertukar menjadi tidak berwarna [1m] Overall reaction equation: Persamaan tindak balas keseluruhan: Zn + CuSO 4 ZnSO 4 + Cu [2m]

Section B Bahagian B. [20 marks] [20 markah] Answer any one questions from this section. Jawab mana-mana satu soalan daripada bahagian ini.

Section B Bahagian B. [20 marks] [20 markah] Answer any one questions from this section. Jawab mana-mana satu soalan daripada bahagian ini. Section B Bahagian B [20 marks] [20 markah] Answer any one questions from this section. Jawab mana-mana satu soalan daripada bahagian ini. 1. (a) What is meant by electrolysis? Apakah yang dimaksudkan