HCI H1 Chem Prelim P 1

HWA CHONG INSTITUTION C2 PRELIMINARY EXAMINATIONS H1 CHEMISTRY 8872 PAPER 1 16 September 2008 50 min Do not open this booklet until you are told to do so. INSTRUCTIONS TO CANDIDATES 1. Check that there are 9 printed pages in this question booklet. 2. There are thirty 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 Optical Mark Sheet provided. 3. Fill in your particulars on the optical mark sheet. Enter your NRIC number or FIN number and shade accordingly. 4. After the examination, you are required to submit only the optical mark sheet. INFORMATION FOR CANDIDATES Each correct answer will score one mark. Marks will not be deducted for wrong answers. A Data Booklet is provided. You may use a calculator. Any rough working should be done in this booklet. This question booklet consists of 9 printed pages.

SECTION A For each question, there are four possible answers, A, B, C, and D . Choose the one you consider to be correct. 1 A giant molecule contains a large amount of carbon of isotopes 12C and 13C. It was found that the relative atomic mass of carbon in the molecule is 12.20. What is the ratio of 12C to 13C in the molecule? A 4:1 B 3:1 C 3:4 D 1:4 2 Oxides of nitrogen are pollutant gases which are emitted from car exhausts. When a car travels one kilometer in urban traffic, it releases 0.23 g of an oxide of nitrogen NxOy, which occupies 120 cm3 under room conditions. What are the values of x and y? A x = 1, y = 1 B x = 1, y = 2 C x = 2, y = 1 D x = 2, y = 4 3 The redox reaction between hydrogen sulphide, H 2S, and sulphur dioxide, SO 2, gives elemental sulphur as the only sulphur-containing product. How many moles of sulphur dioxide react with one mole of hydrogen sulphide? A 3 1 B 2 1 C 3 2 D 1 4 10 cm 3 of 0.2 mol dm -3 K 2XO4 will just react with 40 cm 3 of 0.1 mol dm -3 iron(II) sulphate solution. If Fe2+ is oxidized to Fe3+ by K2XO4, what is the final oxidation state of X? A +2 B +3 C +4 D +5 5 Which of the following particles would have a half-filled set of p orbitals on losing an electron? A Si− B P C PP − D S+ 6 Which of the following molecules does not have a permanent dipole? A C2Cl4 B CF2Cl2 C CHCl3 D CF2CCl2 2008 HCI H1 Chemistry Preliminary Examination / Paper 1 2

7 Which of the following statements about covalent and/or ionic compounds is correct? A A covalent compound cannot be an electrolyte. B Compared to ionic compounds, covalent compounds are generally more soluble in polar solvents. C A covalent compound that contains both hydrogen and oxygen in its molecule necessarily forms intermolecular hydrogen bonds. D Both covalent and ionic bonds may be present in the same compound. 8 Which of the following will have a positive ΔH value? A O2−(g) → O2−(aq) B ½O 2(g) → O(g) C 2Na +(g) + O2−(g) → Na2O(s) D NaOH(aq) + HC l(aq) → NaCl(aq) + H2O(l) 9 In an experiment, a student placed 20 cm 3 of a solution containing 0.040 mol of HC l in a plastic cup and added 20 cm 3 of a solution containing 0.040 mol of Na 2CO3. The highest temperature rise was 15 K. If the heat capacity per unit volume of the final solution is 4.2 J K −1 cm−3, what is the enthalpy change of reaction in J mol−1? A 020 . 0 15 2 . 4 20× ×− B 040 . 0 15 2 . 4 20××− C 020 . 0 15 2 . 4 40× ×− D 040 . 0 15 2 . 4 40××− 10 Consider the following equilibrium reaction: 3Fe(s) + 4H 2O(g) ⇌ Fe3O4(s) + 4H2(g) Which of the following gives the units for the equilibrium constant, K c? A mol dm−3 B mol−2 dm6 C mol4 dm−12 D no units 11 At 298 K, the numerical values for the dissociation constant of the aliphatic carboxylic acids, RCO 2H and R 1CO2H in aqueous solution are 2.1 x 10 -8 and 2.2 x 10 -4 respectively. Which of the following can be inferred from the given information? A The pH of 1 mol dm -3 RCO2H is lower than the pH of 1 mol dm-3 R1CO2H. B The value of K b for RCO2 − is greater than that for R1CO2 −. C RCO 2H is a stronger acid than R1CO2H. D RCO 2H is more soluble in water than R1CO2H. 2008 HCI H1 Chemistry Preliminary Examination / Paper 1 3

12 20.0 cm 3 of 0.10 mol dm −3 sulphuric acid was mixed with 22.0 cm 3 of 0.12 mol dm −3 aqueous ammonia. What is the pH of the resulting solution? A 1 B approximately 1.79 C slightly less than 7 D greater than 7 13 The hydrolysis of sucrose in aqueous solution is catalysed by hydrogen ions, such as from hydrochloric acid. Which of the following procedures can be used to determine the order of the reaction with respect to hydrogen ions? A Measure the rate of the reaction several times, but with a different concentration of hydrochloric acid each time. B Add a suitable indicator and watch for the time when the colour changes. C Remove samples at various time intervals and titrate against a standard solution of sodium hydroxide. D Measure the change in pH during the reaction. 14 A radioactive element has two isotopes, G and H, with half-lives of 5 min and 15 min respectively. An experiment starts with 4 times as many atoms of G as of H. Radioactive decay is a first-order reaction. How long will it be before the number of atoms of G left equals the number of atoms of H left? A 5 min B 10 min C 15 min D 30 min 15 Consider the oxides of the Period 3 elements. Which property decreases from Na 2O to SiO2 and also from SiO2 to P4O10? A covalent character B melting point C pH when mixed with water D solubility in aqueous alkali 16 Aluminium is the third most abundant element in the Earth’s crust. Which of the following statements is not true of the element and its compounds? A Aluminium oxide dissolves in aqueous acids but not aqueous alkalis. B A solution of aluminium chloride turns blue litmus red. C Aluminium chloride can be prepared by passing chlorine gas over heated aluminium metal. D Aluminium fluoride has a much higher melting point than aluminium bromide. 2008 HCI H1 Chemistry Preliminary Examination / Paper 1 4

17 Which statement about the reactant Bi2O3 is true based on the reaction below? Bi 2O3 + 6HNO3 → 2Bi(NO 3)3 + 3H2O A It acts as an oxidising agent. B It acts as a reducing agent. C It is an amphoteric oxide. D It acts as a base. 18 How many σ and π bonds are there in a molecule of the following compound? O σ π A 5 4 B 7 2 C 8 1 D 15 2 19 How many structural and geometric isomers are there altogether for dibromoethene, C2H2Br2? A 1 B 2 C 3 D 4 20 Saccharin is an artificial sweetening agent used in some soft drinks and is manufactured from methylbenzene by the following series of reactions: C NO SO2 H CH3 CH3 SO2Cl CH3 SO2NH2 SO2NH2 COOH saccharin Which of the following types of reactions is not involved in the series? A reduction B condensation C oxidation D substitution 2008 HCI H1 Chemistry Preliminary Examination / Paper 1 5

21 Chlorofluoroalkanes are commonly used as aerosol propellents. However, they cause depletion to the ozone layer when they rise into the stratosphere. It has thus been suggested that fluoroalkanes should be used instead. Which of the following could be a possible reason for the suggestion? A Fluoroalkanes are less volatile than chlorofluoroalkanes and do not reach the stratosphere as easily. B Fluorine radicals are not produced as the C-F bonds are stronger than the C-C l b