DHS 2008 Prelim - H1 Chemistry Paper 2

This question paper consists of 12 printed pages and 0 blank page. [Turn over CANDIDATE NAME ____________________________ CLASS________ DUNMAN HIGH SCHOOL (SENIOR HIGH) YEAR 6 PRELIMINARY EXAMINATION 2008 H1 CHEMISTRY Paper 2 8872/02 17 September 2008 2 hours Candidates answer Section A on the Question Paper Additional Materials: Data Booklet Answer Paper INSTRUCTIONS TO CANDIDATES 1 Write your name and class on this question paper and on all the work you hand in. 2 A Data Booklet is provided. 3 You may use a calculator. 4 The number of marks is given in brackets [ ] at the end of each question or part question. 5 At the end of the examination, fasten all your work securely together with this question paper. Section A 6 Answer all questions. 7 Write your answers in the spaces provided on the question paper. Section B 8 Answer two questions on separate answer paper. FOR EXAMINER’S USE Section A Section B Total % Question 1 2 3 4 5 6 7 Marks 14 9 8 9 20 20 20 [80]

2 © DHS 2008 8872/02 [Turn over Section A Answer all the questions in this section in the spaces provided. 1(a) The graph below shows the trend in a particular property of Period 3 elements. (i) Label on the y–axis of the graph, the property represented. (ii) Briefly explain the trend of this property. [4] (b) One student, Mr Piah, is given three aqueous solutions of the oxides of three Period 3 elements. He adds the indicator, thymol blue, to the three unknown solutions separately and noted the colours of the solutions. (i) With reference to the pH range and colour of thymol blue indicator, identify each of these solutions in the spaces provided below. pH range pH < 1.2 2.8 < pH < 8.0 pH > 9.6 colour of thymol blue red yellow blue solution colour observed identity of oxide 1 green 2 blue 3 red Ionic radius /nm • • • • • • proton number | 11 | 13 | 14 | 15 | 16 | 17 | 18 | 12 •

3 © DHS 2008 8872/02 [Turn over (ii) Briefly outline the reaction of these oxides with water, supporting your answer with appropriate equations. [4] (c) One of the clearest ways in which atomic pr operties influence chemical behavior appears in the diagonal relationships of elements. One such example is beryllium and aluminium, from Group II and III respectively. Their oxides show similar chemical behaviour towards acids and bases. Write equations to show the reactions of beryllium oxide with the following: NaOH (aq) : BeO + 2HCl Æ BeCl2 + H2O HCl (aq) : [2]

4 © DHS 2008 8872/02 [Turn over (d) Nickel is a silvery–white metal that takes on a high polish. It is a transition metal and is hard and ductile. Naturally occurring nickel is composed of five stable isotopes. A mass spectrometer provides the following information about the relative abundance of the five isotopes. isotope relative abundance / % 58Ni 68.08 60Ni 26.22 61Ni 1.14 62Ni 3.63 64Ni 0.93 (i) Define the term relative isotopic mass. (ii) Using the information, calculate the relative atomic mass of nickel to 4 significant figures. Show your working. (iii) The most common oxidation state of nickel is +2. For the 58Ni2+ ion, state the number of protons the number of neutrons the number of electrons [4] [Total: 14]

5 © DHS 2008 8872/02 [Turn over 2(a) Squalene is a natural unsaturated hydrocarbon found in high concentration in the livers of sharks. It is widely used in cosmetics as a moisturiser. Traditionally, squalene is obtained primarily from sharks, though there are botanic sources as well, such as rice bran and olives. In recent years, many cosmetic manufacturing companies are moving away from the use of shark–based squalene and switching to plant–based squalene instead. (i) Suggest two reasons why these companies are switching to use plant–based squalene. (ii) A 0.100 mol sample of squalene reacted with 14.4 dm 3 of hydrogen, measured at r.t.p, to form saturated hydrocarbon C 30H62. Calculate how many double bonds there are in each molecule of squalene. Hence, suggest the molecular formula of squalene. (iii) Write a balanced equation to show how the saturated hydrocarbon C 30H62 reacts with chlorine to form C30H61Cl and state the type of reaction involved. [6]

6 © DHS 2008 8872/02 [Turn over (b) Another unsaturated compound used in cosmetics is Geraniol. geraniol CH2CH2 C C CH2OH CH3 CCH3C CH3 H H (i) Determine how many geometric isomers can geraniol exhibit. (ii) Draw all the possible geometric isomers of geraniol. [3] [Total: 9]

7 © DHS 2008 8872/02 [Turn over 3(a) This table compares the physical properties of some organic compounds: compound melting point / °C solubility in water solubility in organic solvents CH3CH(Cl)COOH –13 Soluble Soluble CH3CH(OH)COOH 26 Soluble Soluble CH3COO–Na+ 325 Soluble Insoluble Account for the difference in melting points between CH 3CH(Cl)COOH, CH3CH(OH)COOH and CH3COO–Na+. [3] (b) Sodium ethanoate, CH 3COO–Na+ is a common product of organic chemistry reactions. In the table below, suggest two organic compounds, each with different functional group that would produce sodium ethanoate via different types of reaction. State the necessary reagents and conditions used and identify one other product formed (if any) in each reaction. structural formula of compound reagents & conditions products CH3COO–Na+ type of reaction: type of reaction: [5] [Total: 8]

8 © DHS 2008 8872/02 [Turn over 4 Propanoic acid, CH 3CH2COOH, is a weak acid. When 50 cm 3 of 0.1 mol dm –3 of propanoic acid is titrated against 0.1 mol dm –3 Ba(OH) 2, a strong base, the following graph was obtained. pH Equivalence pH X Volume of Ba(OH)2 / cm3 (a) Explain what is meant by the term weak acid. [1] (b) (i) Circle on the graph above, the region where a buffer solution is formed. (ii) With the help of suitable equations, explain how the buffer maintains a fairly constant pH when small amounts of NaOH or HCl is added to it. [4] (c) (i) Calculate the volume of Ba(OH)2 required to reach equivalence point. (ii) State a likely value for the equivalence pH and hence suggest a suitable indicator for the titration. equivalence pH value: indicator: [4] [Total: 9]

9 © DHS 2008 8872/02 [Turn over Section B Answer two of the three questions in this section on separate paper. 5(a) When under attack, the bombardier beetle uses ‘chemical warfare’. It defends itself from attack by mixing together solutions of hydrogen peroxide and hydroquinone (C 6H4(OH)2) in the presence of enzymes. This reaction releases free