NYGH 2024 S4SIP Prelim P2 QP

Class Centre/Index Number Name Preliminary Examination 2024 Secondary 4 CHEMISTRY Paper 2 6092/02 1 hour 45 minutes Friday 23 August 0845 – 1030 No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, register number and class in the spaces at the top of this page. Write in dark blue or black pen. You may use a pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid / tape. Section A (70 marks) Answer all questions. Write your answers in the spaces provided. Section B (10 marks) Answer one question. Write your answers in the spaces provided. The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is printed on page 24. The use of an approved scientific calculator is expected, where appropriate. Examiner’s Use Paper 1 Paper 2 Total This document consists of 22 printed pages and 2 blank pages. Setter: TC NANYANG GIRLS' HIGH SCHOOL [Turn over

2 Section A Answer all questions. 1 Choose from the following oxides to answer the questions. Al2O3 CO CO2 CaO H2O Na2O SO2 PbO Each oxide may be used once, more than once or not at all. (a) State the oxide which (i) is produced as a result of incomplete combustion of carbon-containing fuels. [1] (ii) reacts with both acid and alkali. [1] (iii) has a simple molecular structure. [1] (iv) has an ion with an oxidation state of +2. [1] (v) conducts electricity when dissolve in water. [1] (vi) is made during the fermentation of glucose solution to make ethanol. [1] (b) Explain how ethanol can be separated from glucose solution in (a)(vi). [2] [Total: 8]

3 [Turn over 2 This question is about compounds that contain phosphorus. (a) The formula for a phosphide ion can be written as 𝑃𝑃31 15 3-. Complete Table 2.1 to show the number of particles in this phosphide ion. Table 2.1 particle number of particles electron neutron proton [1] (b) State why the formula for the phosphide ion is P3- rather than P2- or P4-. [1] (c) Calcium phosphate, Ca3(PO4)2 is a mineral that aids bone development. (i) Explain, in terms of structure and bonding, if you expect calcium phosphate to have a high melting point. [2] (ii) Calcuate the percentage by mass of phosphorus in calcium phosphate. percentage by mass = % [1] [Total: 5]

4 3 Molybdenum is a transition element which is used to make steel that is extremely hard. It exhibits variable oxidation states and can be manufacture by heating together molybdenum(IV) oxide, MoO2, and aluminium. (a) Construct the equation for this reaction. [1] (b) (i) Complete the table to show the oxidation states of molybdenum and aluminium. element oxidation state in reactants oxidation state in products molybdenum aluminium [2] (ii) In terms of oxidation states, explain why this is a redox reaction. [2] (c) Suggest which metal, molybdenum or aluminium, is less reactive. Explain your answer. [1] (d) Molybdenum has a melting point of 2620 oC. (i) With the help of a labelled diagram, describe the type of bonding that is present in molybdenum. [2]

5 [Turn over (ii) Suggest why molybdenum has a much higher melting point than aluminium. [1] [Total: 9]

6 4 Chlorine, which is an element found in Group 17, is a strong oxidising agent. (a) When chlorine gas is passed into aqueous iron( II) bromide, the colour of the solution changes from yellow to orange. When the orange solution is heated, it gives off a brown vapour, leaving behind a yellow-brown solution S. The brown vapour forms a reddish-brown liquid, element T on cooling. The reddish brown colour disappears when propene is added to T. (i) Name the yellow-brown solution S. [1] (ii) With the help of an ionic equation between the reaction of chlorine and aqueous iron(II) bromide, suggest the identity of T. [2] (iii) Draw the structure of the compound formed when T reacts with propene. [1]

7 [Turn over (b) Chlorine and sodium hydroxide can be manufactured by the electroysis of concentrated aqueous sodium chloride. A simplified diagram of the method of manufacturing chlorine and sodium hydroxide is shown in the diagram below. (i) Write an equation for the reaction occuring at the electrodes. Cathode: Anode: [2] (ii) Suggest a chemical test to confirm the presence of the product at the anode. [1] (iii) Explain why aqeuous sodium hydroxide flows out from the electrolytic cell from the right. [1] (iv) Suggest why the porous divider is placed between the two electrodes. [1] aqueous sodium hydroxide cathode steel anode porous divider product at cathode product at anode concentrated aqueous sodium chloride (electrolyte)

8 (v) The anode is made of steel. Explain why steel is not a suitable material for the anode and suggest a better material that can be used in its place. [2] [Total: 11]

9 [Turn over 5 The chemistry of nickel metal shows a direct resemblance to that of copper. For instance, it usually exists in its compounds in variable oxidation states and forms Ni2+ ions in aqueous solutions. Pure nickel may be obtained from its sulfide ore by the means of the scheme below. (a) Write an equation for the formation of impure nickel in step A and explain fully the environmental effect(s) of the product(s) of the reaction. [3] Ni2S3 NiO + SO2 Ni (impure) Ni (pure) air (step A) carbon

10 (b) Two students looked at the set up below and commented if the set up can be used to purify impure nickel. Student A: I think it will not work as the electrolyte is incorrect. Student B: The electrolyte used is correct but the positions of the pure and impure nickel need to be exchanged. Which student do you agree with? Use your understanding on electrochemistry to explain your choice. [5] concentrated aqueous nickel(II) chloride pure nickel impure nickel