DIRECTORATE FOR QUALITY AND STANDARDS IN EDUCATION Department of Curriculum Management Educational Assessment Unit Track 3 Annual Examinations for Secondary Schools 2015 FORM 3 CHEMISTRY TIME: 1h 30min Name: Class: Useful Data: Atomic numbers and relative atomic masses are shown in the Periodic table printed below. PERIODIC TABLE 1 2 3 4 5 6 7 0 1 H 1 4 He 2 7 Li 3 9 Be 4 11 B 5 12 C 6 14 N 7 16 O 8 19 F 9 20 Ne 10 23 Na 11 39 K 19 24 Mg 12 40 Ca 20 45 Sc 21 48 Ti 22 51 V 23 52 Cr 24 55 Mn 25 56 Fe 26 59 Co 27 59 Ni 28 63.5 Cu 29 65 Zn 30 27 Al 13 70 Ga 31 28 Si 14 73 Ge 32 P 31 32 S 15 16 75 As 33 79 Se 34 35.5 Cl 17 80 Br 35 40 Ar 18 84 Kr 36 85 Rb 37 133 Cs 55 88 Sr 38 137 Ba 56 89 Y 39 139 La 57 91 Zr 40 178 Hf 72 93 Nb 41 181 Ta 73 96 Mo 42 184 W 74 99 Tc 43 186 Re 75 101 Ru 44 190 Os 76 103 Rh 45 192 Ir 77 106 Pd 46 195 Pt 78 108 Ag 47 197 Au 79 112 Cd 48 201 Hg 80 115 In 49 204 Tl 81 119 Sn 50 207 Pb 82 122 Sb 51 209 Bi 83 128 Te 52 210 Po 84 127 I 131 Xe 53 54 210 At 85 222 Rn 86 Key: a X b relative atomic mass symbol atomic number Marks Grid [ For Examiner s use only ] Question N o. Max Mark Actual Mark Section A Section B 1 2 3 4 5 6 7 8 9 10 5 5 7 6 12 14 11 20 20 20 Theory Total Theory Paper: 85% Practical: 15% Final Score: 100% Chemistry Form 3 Secondary Track 3 2015 Page 1 of 7
SECTION A Answer ALL questions. This section carries 60 marks. 1 Give the correct chemical formula for the following substances: a. Potassium chloride b. Magnesium iodide c. Sodium nitrate d. Iron (II) sulfate e. Sulfur dioxide [5] 2 Give the correct chemical name for the following compounds: a. NO2 b. BaSO4 c. H2O d. NaBr e. Al2O3 [5] 3 Jason and Manuel wanted to separate sand from water. In the space provided, draw the set-up required to obtain water from such a mixture. Name the method used and label all apparatus in the set-up. Name of method: [7] Page 2 of 7 Chemistry Form 3 Secondary Track 3 2015
4 What type of bonding exists in the following substances? Explain your reasoning. a. NH3: b. LiBr: c. N2: 5 Complete the following table. Element Number of protons Number of electrons Number of neutrons Ion it can form (a) calcium (b) oxygen (c) aluminium [12] 6 Hydrochloric acid is produced in our stomachs. It has a ph of 1. a. Is HCl a weak or strong acid? b. Name the acid commonly found in vinegar. Chemistry Form 3 Secondary Track 3 2015 Page 3 of 7
c. Complete and balance the following equations: (i) HCl + KOH (ii) HCl + K2CO3 (iii) HCl + K2SO3 (iv) HCl + Mg [12] 7 During an experiment Alison was asked to investigate some magnesium ribbon which is a group 2 metal. a. Write the electronic configuration of magnesium. b. Why is magnesium classified as a group 2 metal? c. What is the mass of one mole of magnesium? d. Using Avogadro s constant (6.02x10 23 ), calculate the number of atoms in 30 g of magnesium. e. Alison burned some of the magnesium ribbon on a Bunsen flame as shown in the diagram. It reacted with oxygen to form white magnesium oxide. (i) Write a balanced equation for this reaction. [3] (ii) If 30 g of magnesium were used in this experiment, what mass of magnesium oxide would be produced? [3] Page 4 of 7 Chemistry Form 3 Secondary Track 3 2015
SECTION B Answer TWO questions only on the foolscap provided. This section carries 40 marks. 8 Atmospheric CO2 levels have increased by more than 40 percent since the beginning of the Industrial Revolution, from about 0.03% in the 1800s to 0.04% today. The resulting greenhouse effect is causing global warming, which is expected to have profound implications, according to many environmental scientists. They argue that if global warming continues unchecked, it will cause significant climate change, a rise in sea levels, increasing ocean acidification, extreme weather events and other severe natural phenomena. a. Name the two most abundant gases in the atmosphere and state their percentage abundance. [4] b. Draw the dot cross diagram of CO2 and write a sentence to explain how you could test for it. [4] c. Cars are said to be a major source of pollution as they burn fossil fuels such as petrol and diesel. Petrol is mostly octane (C8H18). Octane burns in oxygen to give water vapour and carbon dioxide gas. Write a balanced chemical equation for the combustion of octane. [3] d. Name another activity which is also contributing to global warming. e. Other substances such as CFCs also cause aerial pollution. However their effect is different. Explain how CFCs are released in the atmosphere, their effect on the atmosphere and hence on humans. [3] f. Another form of aerial pollution causes acid rain. Name two gases which can form acid rain and name one of their sources. [3] g. Bearing in mind that pollution is harmful to humans and to living things in general, name two measures you could take to reduce your carbon footprint. Chemistry Form 3 Secondary Track 3 2015 Page 5 of 7
9 Sharon, a chemical analyst, parked her green car in a garage and when she returned she found that someone had crashed into it. On the broken bumper she found some red paint which had come off the other car during the crash. As there were three other red cars in the garage she could not tell which one had done the damage. She decided to try to find out who had crashed into her car so she took a sample of paint from the other three cars and the red paint from her bumper. In the lab she found that all the paints were soluble in alcohol. She decided to do the Chromatography test on all four paint samples. a. Explain the words soluble in alcohol. Is alcohol the solvent or the solute? [3] b. Write five sentences to show how Sharon could do the Chromatography test using the four paint samples. c. The chromatogram shows the result obtained by Sharon. [5] (i) Which car crashed into Sharon s car? (ii) How can you tell that the other two cars were not involved in the accident? d. Apart from making coloured paints, dyes are also used in food. A common red food dye is Allura Red AC. It is a dark red powder and is soluble in water. Its molecular formula is C18H14N2Na2O8S2. (i) Calculate the relative molecular mass of Allura Red AC. (ii) Find the percentage of sodium in this molecule. (iii) Write the empirical formula of Allura Red AC. e. Allura Red AC is classified as an artificial additive. In 2007, food scientists in USA found that consumption of the chemical by children can lead to increased hyperactivity. In view of these observations, give two suggestions to control the use of this dye. Page 6 of 7 Chemistry Form 3 Secondary Track 3 2015
10 Water is a transparent liquid that is a major constituent in the body of living things. It consists of two atoms of hydrogen bonded to one atom of oxygen by covalent bonds. However, there are two other elements which have the same proton number as hydrogen; these are Deuterium and Tritium. Deuterium has 1 neutron while Tritium has 2 neutrons. a. Write two properties of ionic compounds and two of covalent compounds. b. What word can be used to describe Hydrogen, Deuterium and Tritium? c. CuSO4.xH2O is a blue powder which when heated becomes white as it loses water. In an experiment, the initial mass of hydrated copper (II) sulfate was 12.35 g and the mass of anhydrous copper (II) sulfate produced was 7.9 g. (i) What is the name given to the water molecules in the hydrated CuSO4? (ii) What mass of water was lost when the hydrated CuSO4 was heated? (iii) Using the values in the above question, find the value of x. d. Solid NaOH absorbs water vapour when exposed to air. It forms a concentrated alkaline solution. (i) What word is used to describe this property of NaOH? (ii) Write a balanced chemical equation to show what happens when aqueous ammonium chloride and sodium hydroxide are mixed and heated together. e. Concentrated sulfuric acid absorbs water vapour when exposed to air. [4] [4] [3] (i) (ii) Name this property of sulfuric acid. This acid changes anhydrous copper (II) sulfate from blue to white. Name this process and write a balanced chemical equation for this reaction. [4] Chemistry Form 3 Secondary Track 3 2015 Page 7 of 7
Chemistry Track 3 Page 7 Question 10 e (ii) The word anhydrous should be hydrated