2023 NBSS Chem Prelims P1

O NORTHBROOKS SECONDARY SCHOOL Preliminary Examination 2023 Secondary 4 Express CANDIDATE NAME CLASS INDEX NUMBER CHEMISTRY 6092/01 Paper 1 Select a time zone. 15 September 2023 1 hour Additional Materials: Multiple Choice Answer Sheet READ THESE INSTRUCTIONS FIRST Write your name, class and index number on all the work you hand in. Write in soft pencil. Do not use staples, paper clips, highlighters, glue or correction fluid/tape. There are forty 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 Multiple Choice Answer Sheet. 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. A copy of the Periodic Table is printed on page 16. The use of an approved scientific calculator is expected, where appropriate. DO NOT TURN THE PAGE UNTIL YOU ARE TOLD TO DO SO. This document consists of 16 printed pages. Setter: Miss Agnes Mok

2 Use the following information to answer Questions 1 and 2. When solid hydrated barium hydroxide is added to a known quantity of solid ammonium chloride, the temperature of the mixture decreases. The chemical reaction is represented by the balanced chemical equation shown below. Ba(OH)2.8H2O (s) + 2NH4Cl (s) → 2NH3 (g) + 10H2O (l) + BaCl2 (s) 1 An experiment is designed to measure the temperature change when all the solid hydrated barium hydroxide reacts with the ammonium chloride. The following pieces of apparatus are available. 1 gas syringe 2 stopwatch 3 electronic mass balance 4 Styrofoam cup Other than a thermometer, which piece(s) of apparatus is(are) needed for this experiment? A 1, 2 and 3 only B 1 and 2 only C 3 and 4 only D 4 only 2 Which diagram shows the correct way of drying and collecting the gas produced? A B C D c gas concentrated sulfuric acid calcium oxide gas gas concentrated sulfuric acid calcium oxide water gas

3 3 Caffeine is a white solid that melts at 235 °C. A sample of impure caffeine is found to be contaminated with sugar. Propanone is an organic solvent with a low boiling point. Caffeine and sugar have different solubilities in water and propanone. substance solubility in water solubility in propanone caffeine moderate high sugar high insoluble The following steps could be carried out to obtain pure caffeine from a mixture of caffeine and sugar. I add excess water II add excess propanone III cool and crystallise IV filter the mixture V heat the filtrate In what order should the steps be carried out? A I, IV, III and V B I, IV, V and III C II, IV, III and V D II, IV, V and III 4 Rf values are used to identify unknown substances using paper chromatography. Which statements about Rf values are correct? 1 Rf values are always less than 1.0. 2 Rf value = distance travelled by solvent ÷ distance travelled by unknown substance. 3 The higher the Rf value, the further the unknown substance travels. 4 Rf value is not affected by the solubility of the unknown substance. A 1 and 2 only B 1 and 3 only C 2 and 3 only D 3 and 4 only 5 Substance M melts at –7.0 °C and is a brown liquid at room temperature. At which temperature(s) will pure M boil? A –77.0 °C B –7.0 °C to 7.0 °C C 48.0 °C to 65.0 °C D 59.0 °C

4 6 An aqueous solution of zinc sulfate is tested by adding reagents. Which observation is correct? reagent added to zinc sulfate result A aqueous sodium hydroxide forms a white precipitate, soluble in excess of the reagent B aqueous ammonia forms white precipitate, insoluble in excess of the reagent C acidified aqueous barium nitrate forms a yellow precipitate D powdered copper forms a grey precipitate 7 The diagram shown is set up using different gases in two beakers P and Q. The inverted smaller beakers both contain oxygen gas. Which gases, when placed in beakers P and Q respectively, will cause the water level at R to rise initially? P Q A ammonia nitrogen B argon oxygen C carbon dioxide nitrogen D oxygen carbon dioxide

5 8 The table below shows information about elements flerovium, Fl, and livermorium, Lv. element Fl Lv proton number 114 116 nucleon number 289 292 Which statement about the elements is correct? A A Lv2+ ion has the same number of electrons as an atom of Fl. B A Fl2+ ion has the same number of protons as an atom of Lv. C An atom of Fl has two more electrons as an atom of Lv. D An atom of Lv has one fewer neutron than an atom of Fl. 9 A sample of a pure solid substance was heated until it turns completely gaseous. The graph below shows the heating curve obtained from the experiment. Which statement is not correct? A At time interval AB, the average kinetic energy of the particles remains the same. B At time interval BC, the substance exists in both solid and liquid states. C At time interval CD, heat is absorbed by the particles. D At time interval EF, the particles are moving rapidly in any direction. 10 Naturally-occurring bromine has a relative atomic mass of 80 and consists entirely of two isotopes of relative atomic masses 79 and 81. What can be deduced about naturally-occurring bromine from the given information? A Bromine is radioactive. B Bromine has different oxidation states. C Bromine isotopes have different number of protons. D Bromine contains the two isotopes in equal proportions. temperature/ oC A B C D E F time

6 11 Which statement about metals is correct? A Layers of electrons can slide over one another making metals malleable. B Metals consist of a lattice of positive ions in a sea of delocalised electrons. C Metals consist of a lattice of positive ions in a sea of delocalised negative ions. D Metals conduct electricity because positive ions are free to move. 12 Poly(acrylic acid) is a very absorbent organic compound used in diapers. The structure of the monomer, acrylic acid, is shown below. How many outer shell electrons of acrylic acid are not involved in bonding? A 0 B 8 C 18 D 20 13 Graphane, an allotrope of carbon, has a structure similar to graphite. Graphane, however, has one hydrogen atom attached to each carbon as shown in the diagram. Which set of properties will graphane have? 1 It is soluble in water. 2 It has a high melting point. 3 It has a giant covalent structure. 4 It conducts electricity in the solid state. A 1 and 2 only B 2 and 3 only C 1, 2 and 3 only D 1, 2, 3 and 4 hydrogen carbon

7 14 The chemical formula of sodium chlorate( VII) is NaC lO3 and the chemical formula of thallium chlorate(VII) is Tl(ClO3)3. What is the chemical formula of thallium sulfate? A TlSO4 B Tl3SO4 C Tl(SO4)2 D Tl2(SO4)3 15 Which quantity contains the least number of atoms? A 0.6 moles of oxygen gas B 0.75 moles of lithium C 0.25 moles of ammonia D 0.25 moles of methane 16 N2O4 is a poisonous gas. It can be removed safely by reaction with aqueous sodium hydroxide. N2O4(g) + 2NaOH(aq) → NaNO3(aq) + NaNO2(aq) + H2O(l) What is the minimum volume of 0.8 mol/dm 3 aqueous sodium hydroxide needed to remove 0.02 mol of N2O4? A 12.5 cm3 B 25.0 cm3 C 50.0 cm3 D 100.0 cm3 17 Which pair of statements correctly describes the differences between the conduction of electricity by electrolytes and the conduction