2022 MSS Chem Prelims P2

Name: ……………………………………………… ( ) Class: ……………… Secondary 4 Express CHEMISTRY 6092/02 Paper 2 24 Aug 2022(Wed) 1 hour 45 minutes READ THESE INSTRUCTIONS FIRST Write your name, class and register number on all the work you hand in. Write in dark blue or black pen. You may use a pencil for any diagrams, graphs, tables or rough working. Do not use staples, paper clips, glue or correction fluid. Section A [50 marks] Answer all questions in the spaces provided. Section B [30 marks] Answer all three questions, the last question is in the form either/or. Answer all questions in the spaces provided. At the end of the examination, fasten all your work securely together. 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 22. The use of an approved scientific calculator is expected, where appropriate. This document consists of 22 printed pages. Setter: Mr Ramesh MONTFORT SECONDARY SCHOOL PRELIMINARY EXAMINATION 2022

2 Section A (Total 50 marks) Answer all the questions in the spaces provided. A1 Name the method of separation used in each of the following processes. [4] Process Method of separation (a) To obtain iodine from a mixture of iodine and sodium chloride. (b) To obtain petrol from a mixture of water and petrol. (c) To obtain the salt formed when hydrochloric acid reacts with sodium hydroxide. (d) To obtain butane from crude oil. (e) To obtain the product formed when carbon dioxide is bubbled into calcium hydroxide. [Total:4]

3 A2 The table shows some information about substances A to D. substance melting point/ °C boiling point/ °C Does it conduct electricity when it is a solid? Does it conduct electricity when molten? A -7 59 no no B 1251 1970 no yes C 1240 2100 yes yes D 1650 2230 no no (a) Use only the letters A, B, C or D to answer the following questions. (i) Which substance is most likely to be a metal? ……………………………………………………………………… [1] (ii) Which substance is a reddish brown liquid at room temperature and which could be used to test if an organic compound is saturated? ………………………………………………………………………..[1] (iii) Which substance is most likely to be sand? ………………………………………………………………………..[1] (b) (i) What type of bonding is present in substance B? ………………………………………………………………………..[1] (ii) Explain your answer. …………………………………………………………………………... ………………………………………………………………………...... ………………………………………………………………………..[2] [total:6]

4 A3 (a) Complete the following table about the preparation of soluble salts. Give the chemical formulae of all reagents and salts which are to be used in the preparation of the salts. method number type of method reagent 1 reagent 2 soluble salt formed 1 Reacting an acid with a metal sulfuric acid, H2SO4 2 Reacting an acid with an insoluble base copper(II) sulfate, CuSO4 3 Reacting an acid with an insoluble carbonate Magnesium carbonate, MgCO3 4 sodium chloride, NaCl [5] (b) Write a balanced ionic equation for any one of the above reactions. [1] (c) Explain why copper(II) sulfate and sodium chloride cannot be prepared using method 1. ………………………………………………………………………………….. ………………………………………………………………………………….. ……………………………………………………………………………….[2] [total:8]

5 A4 When sodium is burned in air, a mixture of sodium oxide, Na2O, and sodium peroxide, Na2O2, is formed. The mixture reacts with water according to the following equations. Na2O + H2O 2 NaOH Na2O2 + H2O 2 NaOH + H2O2 The following information will allow you to calculate the relative amounts of the two oxides produced when sodium is burned. The mixture obtained by burning a sample of sodium was dissolved in distilled water and made up to 100 cm3 to give solution H. (a) A 25.0 cm3 portion of solution H was titrated with 0.100 mol/dm3 hydrochloric acid with methyl orange as the indicator. 22.5 cm3 of the acid was required to reach the end point. Calculate the total amount in moles of NaOH in 100 cm3 of solution H. [2] (b) The H2O2 content of solution H was found by titration of another 25.0 cm3 portion with 0.0200 mol/dm3 KMnO4. The following reaction occurs. 2MnO4‾ + 5H2O2 + 6H+ 2Mn2+ + 5O2 + 8H2O 10.0 cm3 of KMnO4 solution was required to reach the end point. (i) How was the end point determined in the two different titrations? ………………………………………………………………………….. ………………………………………………………………………….. ……………………………………………………………………….[2]

6 (ii) Calculate the amount in moles of the H2O2 in 100 cm3 of solution H. [2] (c) Hence, calculate the amount in moles of Na2O and Na2O2 formed during the burning of the sodium sample. [2] (d) Complete the table below to suggest the oxidation states of the oxygen in each oxide. oxide oxidation state of oxygen sodium oxide, Na2O sodium peroxide, Na2O2 [2] [total:10]

7 A5 A toilet cleaner contains the acid salt, sodium dihydrogen phosphate, NaH2PO4. Sodium dihydrogen phosphate can be made by reacting sodium hydroxide with phosphoric acid. NaOH (aq) + H3PO4 (aq) → NaH2PO4 (aq) + H2O (l) Sodium dihydrogen phosphate reacts with sodium hydroxide to form sodium hydrogen phosphate. NaOH (aq) + NaH2PO4 (aq) → NaHPO4 (aq) + H2O (l) (a) Explain why sodium dihydrogen phosphate is both an ‘acid’ and a ‘salt’. …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... ………………………………………………………………………………..[2] (b) (i) Write an ionic equation for the reaction between sodium hydroxide and phosphoric acid. [1] (ii) Suggest the name and formula of the other salt formed from sodium hydroxide and phosphoric acid. …………………………………………………………………………... ………………………………………………………………………[2]

8 (c) The table shows information about other acidic compounds. name pH of a 0.5 mol/dm3 solution Increasing acid strength sodium dihydrogen phosphate 4.5 ethanedioic acid 3.0 sulfuric acid 1.0 (i) Explain why sulfuric acid behaves as a strong acid but ethanedioic acid behaves as a weak acid. …………………………………………………………………………………... …………………………………………………………………………………... …………………………………………………………………………………... ………………………………………………………………………………..[2] (ii) Both sulfuric and ethanedioic acids are dibasic. Describe an experiment, other than measuring pH, that you could carry out to show that sulfuric acid is a strong acid but ethanedioic acid is a weak acid. State what measurements you would make and what results you would expect. …………………………………………………………………............ ………………………………………………………………………….. ………………………………………………………………………….. ………………………………………………………………………….. ………………………………………………………………………….. ………………………………………………………………………….. ………………………………………………………………………….. ………………………………………………………………………….. ………………………………………………………………………….. ………………………………………………………………………….. ………………………………………………………………………….. ………………………………………………………………………..[3] [total:10]

9 A6 State if the statements below are true (T) or false (F) in the brackets provided. If it is