NJC MCQ Final Prelim

Candidate Name: ____________________________________ Class: ________ National Junior College JC2/IP4 Preliminary Examination 2008 H1 CHEMISTRY (8872/1) Paper 1 10 September 2008 TIME: 50 mins INSTRUCTIONS TO CANDIDATES Do not open this booklet until you are told to do so. Write your NAME, the SUBJECT TITLE , your class and registration number on the optical mark sheet provided. There are 30 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 2B pencil in the optical mark sheet. Submit the optical mark sheet at the end of the examination. INFORMATION FOR CANDIDATES Each correct answer will score one mark. A mark will not be deducted for a wrong answer. A Data Booklet is provided. You may use a calculator. This question paper consists of 12 printed pages (including this page) Shade the index no. in 5 digit format (ABCDE) A: Year of admission 7 = JC2 (2007) 5 = IP (2005) BC: civics class DE: registration no. Eg: 07S0109 = 70109 04IP0215 = 50215 Tan Ah Teck H1 Chemistry Prelims 2008 07S0109 1

1 Which one of the following has the same number of particles as one mole of copper atoms? A The number of ions in 2 dm 3 of 0.25 mol dm−3 of aqueous nitric acid. B The number of delocalised electrons in one mole of magnesium metal. C The number of atoms in 71 g of chlorine gas. D The number of ions in 58.5 g of sodium chloride. 2 Use of the Data Booklet is relevant to this question. The components of a 100 g sample of fertilizer is as shown in the table below: Element Mass / g N 15 P 30 K 15 Other Elements 40 The recommended usage of fertilizer is 14 g of fertilizer per 5 dm3 of water. What is the concentration of nitrogen atoms in this recommended solution? A 0.03 mol dm −3 C 0.42 mol dm−3 B 0.05 mol dm−3 D 0.75 mol dm−3 3 Which one of the following pairs of ions contains two underlined elements having the same oxidation number? A Cl O4 − SO4 2− B MnO4 − MnO4 2− C CrO4 2− Cr2O7 2− D CO3 2− NO3 − 2

4 Which one of the following shows the correct bond angles x, y and z for ethanoic acid as shown below? x y z A 90 180 180 B 90 90 180 C 109.5 120 120 D 109.5 120 105 x H CC O OHH H z y 5 Which one of the following pairs of molecules have the same shape? A CO 2 and H2O B BF3 and NH3 C NH3 and PF3 D CH4 and SF4 6 Which one of the following cannot be explained by hydrogen bonds? A CH 3CHO has a higher boiling point than C2H6. B CH3COOH has a Mr of 120 in benzene. C HF has a higher boiling point than HCl. D CH3COCH3 is miscible with water. 7 Which one of the following electronic configuration represents an element that forms a simple ion with a charge of −2? A 1s2 2s2 2p6 3s2 B 1s2 2s2 2p6 3s2 3p4 C 1s2 2s2 2p6 3s1 D 1s2 2s2 2p6 3s2 3p5 3

8 How many electrons can an atom with principal quantum number n=1 and n=2 accommodate? A 2 B 8 C 10 D 18 9 Given the following data and energy cycle, determine the enthalpy of hydrogenation of ethene, CH 2=CH2 to ethane, CH3CH3. Compound Enthalpy change of combustion ΔHc θ CH2=CH2 (g) −1411 H2 (g) −286 CH3CH3 (g) −1560 A +137 kJ mol −1 B −137 kJ mol−1 C +1084 kJ mol−1 D −1084 kJ mol−1 CH2=CH2 (g) + H2 (g) CH3CH3 (g) ΔHθ hydrogenation + 3 O2(g) + 3.5 O2(g) + 0.5 O2(g) 2 CO2 (g) + 3 H2O (l) 10 In an experiment, 1.00 g of solid K 2CO3 was added to a polystyrene cup containing 25 cm 3 of 1.0 mol dm −3 aqueous HCl. It was found that the temperature of the solution rose by 2.1 oC. The equation for the reaction is as follows. K 2CO3 (s) + 2 HCl (aq) Æ 2 KCl (aq) + CO2 (g) + H2O (l) Which one of the following is the correct value for the enthalpy of reaction above? (Assume that the heat capacity of the solution is 4.2 J oC−1 cm−3) A − 8.82 kJ mol−1 C − 30.5 kJ mol−1 B − 9.17 kJ mol−1 D − 31.7 kJ mol−1 4

11 Which one of the following equations represents the lattice energy of magnesium bromide? A Mg 2+(s) + 2Br−(s) → MgBr2(s) B Mg2+(aq) + 2Br−(aq) → MgBr2(aq) C Mg2+(g) + 2Br−(g) → MgBr2(g) D Mg2+(g) + 2Br−(g) → MgBr2(s) 12 What is the effect of adding an iron catalyst on the rate constants, k f for the forward reaction and k r for the reverse reaction and on the equilibrium constant K c for the following reaction? N2 (g) + 3 H2 (g) 2 NH3 (g) ΔH = − 92 kJ mol−1 k f k r K c A Increase Decrease Increase B Increase Increase Increase C Increase Increase No change D Increase Decrease No change 13 The rate information below was obtained for the reaction P + Q → products. [P] / mol dm −3 [Q] / mol dm−3 Rate / mol dm−3 s−1 0.01 0.05 1.9 x 10−4 0.02 0.05 3.9 x 10−4 0.02 0.01 4.0 x 10−4 If the rate constant doubles for each 10 oC rise in temperature, which one of the following sets of conditions will give the greatest rate of reaction? [P] / mol dm −3 Temperature /oC[Q] / mol dm−3 A 0.1 0.2 40 B 0.2 0.2 30 C 0.3 0.4 20 D 0.4 0.1 30 5

14 The following graph was obtained for the decomposition of 0.75 mol dm −3 H 2O2, given by the equation below. 2H2O2(aq) → 2H2O(l) + O2(g) What would be the half-life of H 2O2 when the experiment was repeated with 1.5 mol dm−3 of H2O2(aq)? A 3.5 min C 14 min B 7 min D 28 min [H2O2]/ mol dm−3 35 Time/min 30252015105 0 0 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 15 Which one of the following is the correct pH for 20 cm 3 of 0.02 mol dm −3 of Ca(OH)2 (aq)? A 10.6 C 12.3 B 10.9 D 12.6 6

16 Which one of the following graphs shows the changes in pH when water is gradually added to a sample of aqueous sodium hydroxide? A C B D 17 Which element is expected to show the greatest tendency to form some covalent compounds? A Beryllium C Magnesium B Calcium D Sodium pH Volume of water 7 7 pH pH Volume of water 7 pH 7 Volume of water 7

18 The bar chart shows the melting points of a series of consecutive elements arranged in order of increasing atomic number. The elements sodium to chlorine form part of this series. Which bar represents sodium? 19 How many isomers of molecular formula C 8H10 contain a benzene ring? A 2 B 3 C 4 D 5 20 2-methylpropylamine can be produced by the following reaction scheme starting with compound B. B KCN in ethanol C reduction 2-methylpropylamine Which one of the following compounds is B likely to be? A CH3CH2CH2Br B CH3CHBrCH3 C CH3CH2CHO D CH3COCH3 8

21 Samples of 10 cm 3 of the first four members of the alkane series are each mixed separately with 70 cm 3 of oxygen. Each is then burned and the total volume, V, of residual gas was measured again at room temperature and pressure. Which one of the following represents the total volume of the residual gases that would be obtained for each of the alkanes? CH 4(g) C 2H6(g) C 3H8(g) C 4H10(g) A 60 55 45 35 B 60 55 50 45 C 10 20 35 60 D 10 20 40 60 22 Reaction of compound R with excess concentrated H 2SO4 at 170 oC gives 2-methylpropene. Compound R was warmed with acidified potassium dichromate(VI) and the resulting vapour was passed into a test-tube containing diammine silver(I) ions. A silver mirror was obtained. Which one of the following could be compound R? A CH 3CH2CH2CH2OH B CH3CH2CH(OH)CH3 C (CH3)2CHCH2OH D (CH3)3COH 23 The reaction of ethanal, CH 3CHO with HCN in the presence of NaOH is an example of A electrophilic addition B electrophilic substitution C nucleophilic a