CJC Prelim H1 Chem 2008 P1 (with worked soln)

CATHOLIC JUNIOR COLLEGE PRELIMINARY EXAMINATION 2008 CHEMISTRY 8872/01 Higher 1 11 September 2008 Paper 1 Multiple Choice 50 minutes Additional Materials: Multiple Choice Answer Sheet Soft clean eraser Soft pencil (type B or HB is recommended) Data Booklet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use paper clips, highlighters, glue or correction fluid. Write and shade your name, class and NRIC / FIN on the Answer Sheet. There are thirty questions on 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. Read the instructions on the Answer Sheet very carefully. 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. You may use a calculator. There are a total of 9 printed pages including this cover page.

2 Section A For each question there are four possible answers, A, B, C and D . Choose the one you consider to be correct. 1 The Star of Africa , a 530 carats pear-shaped diamond, is the second largest cut diamond in the world. How many atoms of carbon are there in the Star of Africa if 1 carat is equivalent to 200 mg? A 1.06 × 1028 B 1.06 × 1025 C 5.32 × 1027 D 5.32 × 1024 2 An element X can exist in a few oxidation states. 30.00 cm3 of an aqueous solution of 0.400 mol dm -3 X2+ required 40.00 cm 3 of 0.100 mol dm-3 of acidified K2Cr2O7 (aq) for a complete reaction. Cr2O7 2-(aq) + 14H+(aq) + 6e- → 2Cr3+(aq) + 7H2O(l) What is the final oxidation state of X? A +4 B +3 C -1 D 0 3 Which of the following has no unpaired electrons in its valence shell? A Mg + B Si C Cu+ D Fe2+ 4 The successive ionisation energies of an element Y is given below. 787 1577 3231 4356 16091 19784 23783 Which Group does Y belong to? A Group II B Group IV C Group V D Group VI 5 What is the electronic configuration of the atom of the element which is isoelectronic with PH 3? A 1s 2 2s2 2p3 C 1s 2 2s2 2p6 3s2 3p3 B 1s 2 2s2 2p6 D 1s 2 2s2 2p6 3s2 3p6 6 In butanoic acid, CH 3CH2CH2COOH(l), there are covalent bonds, hydrogen bonds and Van der Waals’ forces. Which bonds or forces are broken when butanoic acid undergoes vapourisation? A only hydrogen bonds B covalent bonds and hydrogen bonds C covalent bonds and Van der Waals’ forces. D hydrogen bonds and Van der Waals’ forces. 8872/01/CJC Prelim 08

3 7 Ethanedioic acid has the following structure: CC OO HO OH How many σ and π bonds are there in a molecule of ethanedioic acid? σ π A 3 4 B 5 2 C 5 4 D 7 2 8 Ethanol is much more soluble in water than ethyl ethanoate. Which of the following statements correctly accounts for this phenomenon? A The covalent bonds in the ethanol molecules are weaker than those in the ethyl ethanoate molecules. B Ethanol is a polar molecule but ethyl ethanoate is non-polar. C Ethanol is able to form hydrogen bonds with water but ethyl ethanoate does not. D Both ethanol and ethyl ethanoate are able to form hydrogen bonds with water, but the long carbon chain of ethyl ethanoate affects its solubility. 9 The bond dissociation energy of H-F is 565 kJ mol -1. Which equation correctly describes the reaction whereby 565 kJ of energy is released? A HF(l ) → HF(g) B H(g) + F(g) → HF(g) C HF(g) → H(g) + F(g) D ½ H2(g) + ½ F2(g) → HF(g) 10 The enthalpy change for the reaction given below is -114 kJ mol-1. H2SO4(aq) + 2KOH(aq) → K2SO4(aq) + 2H2O(l) Given that Mg(OH) 2 is a strong base, what would be the expected enthalpy change for the following reaction? 2HCl(aq) + Mg(OH)2(aq) → BaCl2(aq) + 2H2O(l) A -57 kJ mol -1 B -114 kJ mol-1 C -171 kJ mol-1 D -228 kJ mol -1 8872/01/CJC Prelim 08

4 11 Sulphuric acid is produced industrially via the Contact process. One of the steps in the production of the acid involves the oxidation of sulphur dioxide, SO 2 to sulphur trioxide SO3 according to the following equation: SO2(g) + O2 (g) SO3(g) ∆H = -196 kJ mol-1 What is the effect of increasing pressure on the above equilibrium? A The rate of formation of sulphur trioxide decreases. B The equilibrium yield of sulphur trioxide will decrease. C Both the equilibrium yield and rate of formation of sulphur trioxide will increase. D The rate of formation of sulphur trioxide will decrease but the equilibrium yield of sulphur trioxide will increase. 12 The pH of water varies with temperature according to the table below. temperature / °C pH 25 7.0 62 6.5 Which of the following statements is true? A Water is not a neutral liquid at 62 °C. B The concentration of H + ions is higher than the concentration of OH - ions in water at 62 °C. C The ionic product of water, K w decreases at higher temperature. D The ionic dissociation of water is an endothermic process. 13 It is often stated that the rate of a typical reaction is roughly doubled by raising the temperature by 10 °C. Which of the following statements best explains this observation? A Raising the temperature by 10 °C doubles the average energy of each molecule. B Raising the temperature by 10 ° C doubles the average velocity of the molecules. C Raising the temperature by 10 °C doubles the number of molecular collisions in a given time. D Raising the temperature by 10 °C doubles the number of molecules having more than a certain minimum energy. 14 Carbon-dating is a technique commonly used for estimating the age of archeological samples. The amount of carbon-14 isotopes in an organism will decay upon its death with a constant half-life of 5700 years. If the amount of carbon-14 isotopes found in an animal fossil is only 25 % of the amount found in living tissues, what is the estimated age of the animal fossil? A 1425 years old C 5700 years old B 4275 years old D 11400 years old 8872/01/CJC Prelim 08

5 15 The pH of 1.0 mol dm -3 of the 2 chlorides, MgC l2 and AlC l3 are 6.0 and 3.0 respectively. Using the Data Booklet, which of the following will be the most likely pH of 1.0 mol dm-3 of BeCl2? A 2.5 C 6.5 B 4.5 D 8.5 16 The figure below shows the melting point trend of some of the elements from Periods 2 and 3 of the Periodic Table. 8872/01/CJC Prelim 08 Which is the element with atomic number V? V-3 V-2 V-1 V V+1 V+2 Atomic Number Melting point / oC Element Atomic Number A Na 11 B Mg 12 C A l 13 D Si 14 17 Which of the following sets of compounds consists of a giant covalent structure, giant ionic structure and a simple covalent structure? A Sodium ethanoate, phosphoric acid, barium chloride B Ethyl ethanoate, sulphur trioxide, silicon dioxide C Methanoic acid, aluminium sulphate, beryllium chloride D Aluminium chloride, diamond, anhydrous sodium hydroxide 18 Which one of the following structural formulae exists in both cis and trans forms? A CCl 2=CHCH3 C C 6H5CH=C(CH2Cl)2 B C 6H5CH=CFC6H5 D CH 3CH=CH2

6 19 H3COC CH2CH=CHCH3 H3C COCH3 O Compound A Compound B Which of the following reagents