2022 PSS Chem Prelims P1

1 Class Register Number Candidate Name PEIRCE SECONDARY SCHOOL Department of Science GCE ‘O’ Level Preliminary Examination I for Secondary Four Express CHEMISTRY 6092 Wednesday 9 May 2018 0900 – 1000 Time: 1 hour INSTRUCTIONS TO CANDIDATES Write in soft pencil. Do not use staples, paper clips, highlighters, glue or correction fluid. Write your name, Index number on the Answer Sheet in the spaces provided. There are forty questions in this paper. Answer all questions. For each question, there are four possible answers, A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate answer sheet. INFORMATION FOR CANDIDATES Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. A copy of the Periodic Table is printed on page 19. This paper consists of 15 printed pages. Setter: Mr Ashwin Selvarajan ���

2 1 Gas W is contaminated with another gas. The impure gas can be removed using liquid Z. Which apparatus is most suitable for the collection of pure gas W? Impure gas W Impure gas W Impure gas W Impure gas W Liquid Z Liquid Z Liquid Z Liquid Z A B C D ���

3 2 Small crystals of red cobalt(II) nitrate and blue copper(II) sulfate were placed at the centers of separate petri dishes filled with agar jelly. They were left to stand under the same physical conditions. After some time, the colour of each substance has spread out as shown. Dish 1 Dish 2 The lengths of the arrows indicate the relative distances travelled by particles of each substance. Which statement is correct? A Diffusion is faster in dish 1 because the mass of the particles is greater. B Diffusion is faster in dish 2 because the mass of the particles is smaller. C Diffusion is slower in dish 1 because the mass of the particles is smaller. D Diffusion is slower in dish 2 because the mass of the particles is greater. 3 A scientist wishes to separate a mixture of iodine, magnesium chloride and lead(II) chloride. Which of the following is the most appropriate sequence of techniques for the scientist to use? Step 1 Step 2 Step 3 A sublimation dissolution and filtration crystallisation B sublimation fractional distillation dissolution and filtration C dissolution and filtration crystallisation sublimation D dissolution and filtration fractional distillation crystallisation ���

4 4 The following diagrams show the arrangement of particles of a substance at two different temperatures. Which substance could the diagrams represent? Substance Melting point / 0C Boiling point / 0C A B C D −210 −210 −100 −100 −50 −10 −50 −10 5 Liquation is an old method of separating a metal from its ore and is shown in the following diagram. Tin ore, containing iron and lead and other impurities, can be refined to a purer form using this method. The impure tin ore is added from the top of the furnace, which has a sloping hearth. The pure liquid tin is collected at the bottom of the furnace, while the impurities are left behind. What can you deduce about the properties of tin from the method? A It is an inert metal. B It is less reactive than iron and lead. C It is more reactive than iron and lead. D It has a melting point and boiling point lower than those of iron and lead. -190 ºC -30 ºC Metal ore Impurities Sloping hearth Purer liquid metal ���

5 6 Indium (In) with a relative atomic mass of 114.9 consists of two naturally occurring isotopes. One of these isotopes is In-115, with 95.7% abundance. Given that there are 49 protons in an atom of indium, calculate the nucleon number of the second naturally occurring isotope in indium. A 49 B 64 C 113 D 114 7 Four particles W, X, Y and Z have the composition shown in the table below. particle number of electrons atomic number mass number W 10 10 20 X 11 11 23 Y 10 11 23 Z 19 19 39 There are three statements below with regards to particles W, X, Y and Z. 1 Particle X gives away one electron to form particle Y. 2 Particle W and particle Y are isotopes. 3 Substance made of particle Z has a lower melting point than substance X Which of the following statements are correct? A 1 and 2 B 1 and 3 C 2 and 3 D 1, 2 and 3 ���

6 8 The diagram below shows the arrangement of outermost electrons for element P when it reacts with element Q to form a compound. To which groups of the Periodic Table do element P and element Q belong? element P element Q A Group V Group VI B Group V Group VII C Group VI Group I D Group VI Group VII 9 The table provides some information of three particles. charge of particle number of electrons number of neutrons nucleon number 0 18 X 40 1+ 18 20 Y Z 10 8 16 What are the values of X, Y and Z? X Y Z A 18 37 2- B 18 39 2+ C 22 39 2- D 22 37 2+ ���

7 10 Substances with giant covalent structures can be used as lubricants or as cutting tools for hard materials. The diagram shows how the atoms are arranged in two giant covalent structures, X and Y. Which statement is correct? A Only X is used as a cutting tool and only Y is used as a lubricant. B Only X is used as a lubricant and only Y is used a cutting tool. C X and Y are both used as a cutting tool. D X and Y are both used as lubricants. 11 Ethane, C2H6, and ammonia, NH3, are covalent compounds. The “dot-and-cross” diagrams of these compounds are shown. Which statements are correct? 1 A molecule of ethane contains twice as many hydrogen atoms as a molecule of ammonia. 2 An unreacted nitrogen atom has five outer electrons. 3 In a molecule of ethane, the bond between the carbon atoms is formed by sharing two electrons, one from each carbon atom. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only X Y key Strong covalent bond Weak attraction ���

8 12 The active component of tobacco, nicotine, found in cigarette smoke is thought to increase the chances of a person developing lung cancer. The percentage composition of nicotine is 74.0% carbon, 8.7% hydrogen and 17.3% nitrogen. The relative molecular mass of nicotine is 162. What is the molecular formula of nicotine? A C3H2N B C5H7N C C9H6N3 D C10H14N2 13 68 g of hydrogen peroxide is dissolved in water to form an aqueous solution. The solution is heated and decomposes in the presence of manganese( IV) oxide to give 2.4 dm3 of oxygen gas as follows. 2H2O2 → O2 + 2H2O What is the percentage purity of the hydrogen peroxide? (All gases are measured at room temperature and pressure.) A 2.5% B 5.0% C 10.0% D 100.0% 14 Dinitrogen tetraoxide, N2O4, is a poisonous gas. It can be disposed off safely by reaction with sodium hydroxide. In the experiment, the concentration of aqueous sodium hydroxide used is 1.5 mol/dm3. N2O4 (g) + 2NaOH (aq) → NaNO3 (aq) + NaNO2 (aq) + H2O (l) Which of the following is the least volume of aqueous sodium hydroxide required to dispose off 300 cm3 of N2O4 at room temperature and pressure? A 10 cm3 B 20 cm3 C 120 cm3 D 240 cm3 ���

9 15 Which pairs of statements correctly describe the differences between the cond