2022 Presbyterian High Chemistry P3 (Answers)

[Turn over Name: ...................................... Register/Index Number: ............... Class: .............. PRESBYTERIAN HIGH SCHOOL SCIENCE (CHEMISTRY) 5076/3, 5078/3 Paper 3 12 August 2022 Friday 1 hour 15 minutes PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL PRESBYTERIAN HIGH SCHOOL 2022 SECONDARY FOUR EXPRESS / FIVE NORMAL (ACADEMIC) PRELIMINARY EXAMINATION INSTRUCTIONS TO CANDIDATES DO NOT OPEN THIS QUESTION PAPER UNTIL YOU ARE TOLD TO DO SO. Write your class, register number and name on all the work you hand in. Write in dark blue or black pen. Do not use correction fluid. Section A Answer all questions. Write your answers in the spaces provided on the question paper. Section B Answer any two questions. Write your answers in the spaces provided on the question paper. A copy of the Periodic Table is printed on page 13. Setter: Mr Muhammad Faeez Vetted by: Ms Chan Poh Hoon This question paper consists of 13 printed pages. For Examiner’s Use Section A Section B Total 45 20 65

2 [Turn over Section A (45 marks) Answer all questions in the spaces provided. 1 Use the list of elements below to answer the questions that follow. copper sodium chlorine aluminium nitrogen oxygen iron carbon helium bromine In your answers, you may use an element once, more than once, or not at all. Name one element which (a) is used in the manufacture of steel, iron/carbon [1] (b) can displace tin from its compound, sodium/aluminium/iron [1] (c) has six valence electrons, oxygen [1] (d) has a triple bond within its molecule, nitrogen [1] (e) is an inert gas. helium [1] 2 Zinc smelting is a process that converts zinc concentrates ( ores that contain zinc) into pure zinc. One of the last stages involves purifying zinc by fractional distillation in a column made up of silicon carbide. The main impurities in zinc are shown in Table 2.1. Pure zinc has a boiling point of 908 oC. Table 2.1 impurities boiling point /oC cadmium 765 copper 2582 iron 2887 lead 1751 (a) State why it is possible to purify zinc by fractional distillation. It has different boiling points (b) When fractional distillation is carried out, which metal will be distilled first? Cadmium (c) How would you test if the zinc purified from the fractional distillation is free from any impurities? Test the melting point to see if its fixed

3 [Turn over 3 In an experiment, 0.100 g of zinc granules was reacted with excess of 1.00 mol/dm3 hydrochloric acid and the total volume of gas produced was measured every ten seconds until the reaction stopped. The results are shown in Table 3.1. Table 3.1 time from the start of experiment/ s total volume of gas produced/ cm3 0 0 10 31 20 52 30 67 40 78 50 88 60 96 70 100 80 100 (a) Construct a balanced equation for the reaction. Zn + 2HCl → ZnCl2 + H2 (b) Plot a graph of total volume of gas produced against time. [2] (c) (i) How long did it take for the reaction to stop? 70 seconds (ii) Explain why the reaction stops. All the zinc had reacted (d) The experiment was repeated using the same mass of powdered zinc, with the other conditions being kept constant.

4 [Turn over (i) Explain, using the collision theory, how changing from zinc granules to zinc powder affects the speed of reaction. There is an increase in the total surface area Frequency of effective collision increases Speed of reaction increases (ii) Sketch, on the same grid given, a graph of how the volume of gas produced will change for the new experiment. Label this new graph A. [1] 4 Fig 4.1 shows a solution mixture V, which contains two cations and one anion. Fig 4.1 (a) State the identity of the following: (i) white precipitate W barium sulfate/BaSO41] (ii) blue precipitate X copper(ll) hydroxide/ Cu(OH)2 (iii) green precipitate Z iron(ll) hydroxide/ Fe(OH)2 (iv) solution Y aqueous ammonia/sodium hydroxide/ aq NH3/ NaOH (b) Suggest the ions present in mixture V. Fe2+, SO42-, Cu2+ / iron(ll), sulfate, copper(ll) ions 5 (a) Complete Table 5.1. Table 5.1 chemical name chemical formula acidic/basic/neutral/amphoteric calcium oxide CaO basic lead(ll) oxide PbO amphoteric nitrogen monoxide NO neutral [3] mixture V white precipitate W blue precipitate X green precipitate Z deep-blue solution aqueous barium nitrate excess solution Y aqueous ammonia excess aqueous ammonia

5 [Turn over (b) Small pieces of each of the following metals were added to cold water and the volume of gas collected in the first two minutes was recorded in Table 5.2. Table 5.2 metal aluminium barium calcium magnesium potassium volume of gas/ cm3 0 60 25 2 90 (i) Use the data in Table 5.2 to place the metals in order of increasing reactivity. aluminium, magnesium, calcium, barium, potassium (ii) Write an equation, with state symbols, for the reaction between calcium and water. Ca (s) + 2H2O (l) → Ca(OH)2 (aq) + H2 (g) 1M – correct balanced equation 1M – correct state symbols (iii) What would you expect to see if carbon dioxide is passed through the solution remaining from the reaction in (b)(ii)? Give a reason for your answer. White precipitate forms in the solution Calcium carbonate is formed (iv) Explain why aluminium did not produce any gas when added to cold water. It has a layer of oxide which prevents any reaction 6 Table 6.1 below shows the mass of some pollutants found in the exhaust gas when one kilogram of each fuel is burnt. Table 6.1 mass of pollutant/ g fuel carbon monoxide oxides of nitrogen sulfur dioxide petrol 27 30 0.8 diesel 11 60 3.9 (a) (i) Explain why carbon monoxide is found in the exhaust gas. Incomplete combustion of carbon containing fuels/petrol (ii) Explain the effect of carbon monoxide on humans. It reduces the ability of blood to transport oxygen

6 [Turn over (b) Name the element found in both petrol and diesel that is responsible for the presence of carbon monoxide in the exhaust gas. Carbon (c) Using the data in Table 6.1 , name the fuel which is more harmful to the environment when burnt. Explain your answer. Diesel Mass of oxides of nitrogen and sulfur dioxide is larger than that released by petrol (d) The following shows two molecules of alkenes. Fig 6.2 With reference to Fig 6.2, suggest one similarity and one difference between the two molecules. There is a presence of C=C in both molecules while one is branched while the other is straight (e) Alkenes can undergo polymerization to form polymers. (i) Given part of the polymer shown in Fig 6.3, deduce the name of its monomer. Hence draw the structure of the monomer. Fig 6.3 Name of monomer: propene Structure: