NJC 2022 H2 Chemistry Prelim P1 QP

NJC/H2 Chem Preliminary Examination/01/2022 [Turn over NATIONAL JUNIOR COLLEGE SH2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME SUBJECT CLASS REGISTRATION NUMBER CHEMISTRY Paper 1 Multiple Choice Additional Materials: Optical Answer Sheet Data Booklet 9729/01 15 September 2022 1 hour READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, highlighters, 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. 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: 2105648 15648 This document consists of 15 printed pages and 1 blank page.

2 NJC/H2 Chem Preliminary Examination/01/2022 1 Technetium (Tc) is a second row transition element that does not occur naturally on Earth. One of its isotopes has 56 neutrons. What is the nucleon number of this isotope? A 43 B 56 C 99 D 112 2 Which row has the greater number of particles? A 1 mol of liquid sulfuric acid B 12000 cm3 of oxygen gas at s.t.p. C 32.5 g of zinc D 16 g of nitrogen gas 3 Which species will have the smallest deflection when passed through the same electric field? A 23Na+ B 11B3+ C 19F− D 32S2− 4 0.0353 g of a sample of volatile organic compound was completely vaporized at 50 kPa and 300K. The vapour occupied a volume of 40 cm3. On complete combustion in excess oxygen, 80 cm 3 of carbon dioxide and 80 cm 3 of water vapour were formed. All gaseous volumes were measured under identical conditions. What would be the molecular formula of the compound? A C2H2O B C2H4O C C2H6O D C3H8 5 Which species has the most number of unpaired electrons? A Co2+ B N C Fe D S 6 Rubidium and bromine form ions that are isoelectronic. 1 Ionic radius of rubidium is smaller than its atomic radius. 2 Ionic radius of bromine is larger than its atomic radius. 3 Ionic radius of bromine is smaller than that of rubidium. Which statements are correct? A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

3 NJC/H2 Chem Preliminary Examination/01/2022 [Turn over 7 Which row correctly shows the bond angles for α, β, γ in the molecule below? O CH3 NH2a b g α β γ A 109.5o 120o 109.5o B 120o 109.5o 107o C 120o 107o 105o D 120o 109.5o 105o 8 In which pair is the melting point of the second species higher than that of the first species? A C and Si B K and Rb C NaCl and NaBr D SiCl4 and SiO2 9 When liquid N2F4 is heated, it decomposes into a single product, B. Which statements are correct? 1 N–F bonds are broken during this decomposition. 2 The enthalpy change when N2F4 decomposes into B is approximately +160 kJ mol–1. 3 Molecules of B are non-linear. A 1, 2 and 3 B 1 and 2 only C 2 and 3 only D 1 only

4 NJC/H2 Chem Preliminary Examination/01/2022 10 Three experiments were carried out involving acids and alkalis of the same concentration. The temperature changes were recorded as shown in the table below. Volumes of acids and alkalis added together T/ oC 25.0 cm3 of HCl(aq) + 25.0 cm3 of NaOH(aq) T1 50.0 cm3 of HCl(aq) + 50.0 cm3 of NaOH(aq) T2 25.0 cm3 of HCl(aq) + 25.0 cm3 of NH3(aq) T3 Which row shows the correct relative magnitude of T values? A T2 > T3 > T1 B T1 = T2 > T3 C T2 = T3 > T1 D T1 = T2 = T3 11 Some H values are given below. enthalpy change of formation / kJ mol–1 Fe2O3 − 824.2 CO − 110.5 CO2 − 393.5 In the industrial production of iron, iron(III) oxide is reduced by carbon monoxide. What is the enthalpy change of reaction for one mole of iron formed? A − 24.8 kJ mol–1 B + 24.8 kJ mol–1 C − 12.3 kJ mol–1 D + 541.2 kJ mol–1

5 NJC/H2 Chem Preliminary Examination/01/2022 [Turn over 12 Nitrogen and hydrogen form ammonia in an exothermic reaction. The rate and yield of the reaction can be altered by changing the experimental conditions. Which row correctly describes the effect of the changes in condition? change in condition effects equilibrium yield rate of forward reaction rate of backward reaction 1 increasing temperature decreases increases increases 2 increasing temperature increases decreases increases 3 addition of catalyst increases increases no effect 4 addition of catalyst no effect increases increases A 1 and 4 only B 2 and 4 only C 2 and 3 only D 1 and 3 only 13 Four solutions, each of concentration 0.1 mol dm–3, were tested with a pH meter. The results are shown. solution pH CH3CO2H 4 HNO3 1 CH3NH2 11 NaOH 14 Which statement is incorrect? A Conjugate base of CH3CO2H is less stable than that of HNO3. B HNO3 has a lower pH than CH3CO2H because it is more soluble. C NaOH has a higher concentration of hydroxide ions in solution than CH3NH2. D Mixing equal volume of CH3NH2 and HNO3 form a solution with pH less than 7.

6 NJC/H2 Chem Preliminary Examination/01/2022 14 Solid calcium hypochlorite pellets, Ca(C lO)2(s), are added to swimming pools to form HClO(aq) which kills disease-causing bacteria and algae. Ca(ClO)2(s) ⇌ Ca2+(aq) + 2ClO−(aq) ClO−(aq) + H2O(l) ⇌ HClO(aq) + OH−(aq) What is the effect on the solubility of calcium hypochlorite and bacterial growth when pH increases? effect on solubility of calcium hypochlorite effect on bacterial growth A decreases increases B decreases decreases C increases increases D increases decreases 15 A mixture of two oxides of period 3 elements is added to water and the resultant solution has a pH value below 7. What could be the constituents of the mixture? A Al2O3 and MgO B Na2O and MgO C Na2O and P4O10 D SO3 and P4O10 16 Anhydrous magnesium nitrate, Mg(NO 3)2, decomposes when heated, giving a white solid and a mixture of two gases, D and E. E is oxygen. What is the ratio of mass of D released mass of E released ? A 1 0.174 B 1 0.267 C 1 0.348 D 1 3.43

7 NJC/H2 Chem Preliminary Examination/01/2022 [Turn over 17 Addition of warm concentrated sulfuric acid, H 2SO4, to crystals of sodium halides gives the following observations. compound observation NaF evolution of a colourless gas which etches a damp glass rod NaCl evolution of a choking colourless gas which produces a white cloud in contact with ammonia vapour NaBr evolution of a brown vapour and of pungent fumes which turn potassium dichromate(VI) paper green NaI evolution of a purple vapour and a gas smelling of rotten eggs Which statements are consistent with the observations? hydrogen halide is produced in all four reactions H2SO4 is acting as a reducing agent in all four reactions SO2 and H2S are reduction products of H2SO4 A true false true B true true false C false false true D false true false 18 The following electrochemical cell was set up and the Ecell value was found to be +0.018 V. V Ag 0.5 mol dm-3 AgNO3(aq) M N Ag 1.0 mol dm-3 AgNO3(aq) salt bridge Which statement is correct? A Electr