2019 NJC Prelim P1 QP

[Turn over NATIONAL JUNIOR COLLEGE SH2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 1 Multiple Choice Additional Materials: Multiple Choice Answer Sheet Data Booklet 9729/01 Thursday 19 September 2019 1 hour READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name, subject class and registration number on the Answer Sheet in the spaces provided unless this has been done for you. 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. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. Instructions on how to fill in the Optical Mark Sheet Shade the index number in a 5 digit format on the optical mark sheet: 2nd digit and the last 4 digits of the Registration Number. Example: Student Examples of Registration No. Shade: 1805648 85648 This document consists of 12 printed pages.

2 NJC/H2 Chem Prelim/01/2019 1 When a sports medal with a total surface area of 150 cm 2 was evenly coated with silver by electrolysis, its mass increased by 0.216 g. How many atoms of silver were deposited per cm2 on the surface of the medal? A 8.0 × 1018 B 1.8 × 1019 C 1.2 × 1021 D 4.1 × 1022 2 Which species is deflected to the greatest extent in an electric field? A e− B H+ C He2+ D F− 3 In an experiment, 50.0 cm 3 of a 0.10 mol dm –3 solution of M3+ salt reacted exactly with 25.0 cm3 of 0.10 mol dm–3 aqueous sodium sulfite. The half-equation for oxidation of sulfite ion is shown below. SO32−(aq) + H2O(I) → SO42−(aq) + 2H+(aq) + 2e– What is the final oxidation number of M? A +1 B +2 C +4 D +5 4 The graph shows the first thirteen successive ionisation energies for element E. What can be deduced about element E from the graph? A It is in Period 3 of the Periodic Table. B It is a d−block element. C It is in Group 2 of the Periodic Table. D It is aluminium.

3 NJC/H2 Chem Prelim/01/2019 [Turn over 5 What is the order of increasing radii for the three species shown? smallest largest A Ar Ca2+ K+ B Ar K+ Ca2+ C Ca2+ K+ Ar D K+ Ar Ca2+ 6 Organic nitrates in photochemical smog can cause breathing difficulties. The diagram shows an example of an organic nitrate molecule. What is the order of increasing bond angles? A 1 < 2 < 3 B 2 < 1 < 3 C 3 < 1 < 2 D 3 < 2 < 1 7 Two glass vessels F and G are connected by a closed valve. F contains helium at 20 °C at a pressure of 1 × 105 Pa. G has been evacuated, and has three times the volume of F. In an experiment, the valve is opened and the temperature of the whole apparatus is raised to 100 °C. What is the final pressure in the system? A 3.18 × 104 Pa B 4.24 × 104 Pa C 1.25 × 105 Pa D 5.09 × 105 Pa F G

4 NJC/H2 Chem Prelim/01/2019 8 Carbon monoxide burns readily in oxygen to form carbon dioxide. What can be deduced from this information? 1 The +4 oxidation state of carbon is more stable than the +2 state. 2 The standard enthalpy change of formation of carbon dioxide is less negative than that of carbon monoxide. 3 The value of the equilibrium constant for the following reaction is likely to be high. 2CO(g) + O2(g) 2CO2(g) A 1, 2 and 3 B 2 and 3 C 1 and 3 D 1 only 9 Two reactions and their enthalpy changes are shown. 2C(s) + 2H2(g) → C2H4(g) ∆Ho = +52.2 kJ mol–1 C2H2(g) + H2(g) → C2H4(g) ∆Ho = −175.8 kJ mol–1 These data can be used to calculate the enthalpy change for the reaction shown. 2C(s) + H2(g) → C2H2(g) ∆Ho1 What is the value of ∆Ho1? A –228.0 kJ mol–1 B –123.6 kJ mol–1 C +123.6 kJ mol–1 D +228.0 kJ mol–1 10 Butanedioate ions can be dehydrogenated to form trans -butenedioate ions. The enzyme fumarase speeds up this reaction. How does fumarase speed up this reaction? A Fumarase increases the kinetic energy of the reactants. B Fumarase increases the frequency of collisions between reactants. C Fumarase lowers the activation energy of the dehydrogenation reaction. D Fumarase is specific for this dehydrogenation reaction.

5 NJC/H2 Chem Prelim/01/2019 [Turn over 11 The reaction between ethanedioate ions and acidified manganate(VII) ions as shown below takes place very slowly in the cold but can be accelerated with heat or with addition of Mn 2+ catalyst. 2MnO4 + 5C2O42 + 10H+ → 2Mn2+ + 10CO2 + 8H2O The reaction rate for the reaction can be measured by noting the time elapsed for the purple colour of the manganate(VII) ions to disappear. The following results were obtained. Expt Volume / cm3 Time / s C2O42−(aq) MnO4−(aq) Mn2+(aq) water 1 20 30 5 25 30 2 20 30 10 20 15 3 20 15 10 35 15 4 20 20 20 20 10 Which conclusions can be drawn about the reaction? 1 The reaction is first order with respect to Mn2+ (aq). 2 MnO4− is involved in the rate-determining step. 3 The unit of rate constant is mol−1 dm3 s−1. A 1 only B 1 and 2 C 2 and 3 only D 1, 2 and 3 12 In which reactions does NH3 behaves as a Lewis base? 1 2NH3 → NH2− + NH4+ 2 HSO4− + NH3 → SO42− + NH4+ 3 Ag+ + 2NH3 → [Ag(NH3)2]+ A 1 only B 1 and 2 C 2 and 3 D 1, 2 and 3

6 NJC/H2 Chem Prelim/01/2019 13 The numerical values of the solubility products of three metal sulfides are tabulated below. compound numerical value of solubility product CuS 8.5 × 1045 Ag2S 1.6 × 1049 Bi2S3 1.1 × 1073 What is the order of increasing molar solubility of the three metal sulfides in water? A Bi2S3 < Ag2S < CuS B CuS < Ag2S < Bi2S3 C Ag2S < Bi2S3 < CuS D CuS < Bi2S3 < Ag2S 14 A piece of blue litmus paper was soaked in concentrated NaCl solution and supported on a glass slides. The paper was connected to a direct current supply as shown in the diagram below. What are the observations near the negative electrode and the positive electrode after the current had flown for some time? negative electrode positive electrode A blue red B red blue C blue bleached D bleached blue negative electrode positive electrode glass slide blue litmus paper

7 NJC/H2 Chem Prelim/01/2019 [Turn over 15 Which statement does not describe the chemical properties of Period 3 compounds? A SiO2 is formed from the hydrolysis of SiCl4. B Al2O3 is soluble in both acid and base. C Equimolar of Na2O and SO3 can be mixed in water to give a pH neutral solution. D The acidity of Period 3 chlorides in water decreases from NaCl to PCl5. 16 A 5.00 g sample of an anhydrous Group 2 metal nitrate loses 3.29 g in mass when heated strongly. What is the identity of the metal? A magnesium B calcium C strontium D barium 17 Transition lenses are made of photochromic glass. Photochromic glass darkens when exposed to bright light Reaction 1 Ag+ + Cl– Ag + Cl Photochromic glass becomes more transparent again when the light is less bright. Reaction 2 Cu+ + Cl → Cu2+ + Cl– Reaction 3 Cu2+ + Ag → Cu+ + Ag+ Which statement about these reactions is correct? A Ag