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Unformatted text preview: ocafii” RECOGNISING ACHIEVEMENT OXFORD CAMBRIDGE AND RSA EXAMINATIONS Advanced Subsidiary GCE CHEMISTRY 281 1 Foundation Chemistry Friday 12 JANUARY 2001 Morning 1 hour 30 minutes Additional materials: Seientific calculator Data Sheet for Chemistry Candidates answer on the question paper. _ Candidate Candidate Name Centre Number Number _D11:DD:ED TIME 1 hour 30 minutes INSTRUCTIONS TO CANDIDATES 0 Write your name in the space above. 0 Write your Centre number and Candidate number in the boxes above. 0 Answer all the questions. . Write y0ur answers in the spaces on the question paper. . Read each question carefully and make sure you know what you have to do before starting your answer. FOR EXAMINER’S USE INFORMATION FOR CANDIDATES o The number of marks is given in brackets [ ] at the end of each question or part question. a You will be awarded marks for the quality of written communication where this is indicated in the question. . You are advised to show all the steps in any calculations. - You may use a scientific calculator. - You may use a Data Sheet for Chemistry. This question paper consists of 12 printed pages, 2 lined pages and 2 blank pages. SB (NH/CG) QA15720/3 © com 2001 Registered Charity Number 1066969 [Turn over 1 505 1505 2 Answer all the questions. Lithium was discovered in 1817 by the Swedish chemist Arfvedson. Lithium exists naturally as a mixture of isotopes. (a) Explain the term isotopes. .......................................................................................................................................... ...................................................................................................................................... [1] (b) Which isotope is used as the standard against which relative atomic masses are measured? ...................................................................................................................................... [1] (c) The mass spectrum below shows the isotopes present in a sample of lithium. 100 80 60 % composition 40 20 0 0 5 10 15 relative isotopic mass (i) Use this mass spectrum to help you complete the table below for each lithium isotOpe in the sample. isotope percentage composition _--_ ——-- (ii) Calculate the relative atomic mass of this lithium sample. Your answer should be given to three significant figures. [3] [2] 2811 Jan01 Fa Exam: 3 For Examine . . . u (d) The species responsible for the peaks in this mass spectrum are lithium Ions, produced 39 and separated in a mass Spectrometer. (i) How are the electrons removed from lithium atoms to form lithium ions in a mass spectrometer? ............................................................................................................................... [1] (ii) How does a mass spectrometer separate the ions? ............................................................................................................................... [1] (e) The first ionisation energy of lithium is +520 kJ mol“. (i) Define the term first ionisation energy. ............................................................................................................................... [3] (ii) The first ionisation energy of sodium is +496 kJ mol“. Explain why the first ionisation energy of sodium is less than that of lithium. Your answer should compare the atomic structures of each element. ............................................................................................................................... [3] [Total : 15] l 2311 Jano1 [Turn over 1505 1505 4 For Examinl . . . . U Electrons are arranged In energy levels. The diagram below for the 7 electrons In a nitrogen se atom is incomplete. It shows two electrons in the 1s level. .............. EL Wm energy (a) Complete the diagram for the 7 electrons in a nitrogen atom by (i) adding labels for the other sub-shell levels, [1] (ii) showing how the electrons are arranged. [2] (b) Magnesium reacts with nitrogen forming magnesium nitride, which is an ionic compound. (i) Complete the electronic configuration for the 12 electrons in a magnesium atom. 1s2 ........................................................................................................................ [1] (li) What is the charge on each ion in magnesium nitride? magnesium ion ......................................................................................................... nitride ion .............................................................................................................. [2] (iii) Complete the electronic configuration of each ion in magnesium nitride. magnesium ion 1s2 .............................................................................................. nitride ion 1 s2 .......................................................................................... [2] (iv) Deduce the formula of magnesium nitride. ............................................................................................................................... [1] 2811 Jan01 5 For Exam/m (c) Magnesium reacts With carbon dioxide forming a mixture of magnesium oxide, MgO, use and carbon. (i) Write an equation, with state symbols, for this reaction. ............................................................................................................................... [2] (ii) When water is added to the mixture containing magnesium oxide, some of the magnesium oxide reacts to form a solution of magnesium hydroxrde. MgO(s) + H200) ———> Mg(OH)2(aq) Predict the pH of this solution. ............................................................................................................................... [1] [Total : 12] 2811Jan01 [Turn over 1505 , 3 agn: 6 r Calcium carbonate is added to an excess of hydrochloric acid. CaCOa(s) + 2HCl(aq) ———> CaCl.2(aq) + 002(9) + H200) (a) Deduce two observations that you would expect to see during this reaction. observation 1 .................................................................................................................... observation2 ........... [2] (b) In this experiment, 0.0409 CaCO3 is added to 25 cm3 of 0.050 mol dm‘3 HCL (i) Explain what is meant by 0.050 mol dm‘3 HCL ................................................................................................................................... ................................................................................................................................... ............................................................................................................................... [2] (li) Calculate how many moles of CaCO3 were used in this experiment. [2] (iii) Calculate how many moles of HCl are required to react with this amount of CaCOa. [1] (iv) Hence show that the HCl is in excess. [1] (c) State one large-scale use of a named Group 2 compound that is being used to reduce acrdity. ...................................................................................................................................... [1] 2811 Jano1 For Exam/m Use 7 For Examme 4 Water is the most abundant compound on Earth. Much of the chemistry of water is use influenced by its polarity and its ability to form hydrogen bonds. (a) Polarity can be explained in terms of electronegativity. (i) Explain the term electronegativity. ............................................................................................................................... [2] (ii) Why are water molecules polar? ............................................................................................................................... [1] (b) The polarity of water molecules results in the formation of hydrogen bonds. (i) Draw a diagram to show hydrogen bonding between two molecules of water. Your diagram must include dipoles and lone pairs of electrons. [4] (ii) State the bond angle in a water molecule. ............................................................................................................................... [1] (c) State and explain two properties of ice that are a direct result of hydrogen bonding. property ............................................................................................................................ explanation ....................................................................................................................... property ............................................................................................................................ explanation ....................................................................................................................... ...................................................................................................................................... [4] [Total : 12] 2811Jano1 [T urn over 1505 5 1505 8 For Examin Well over 2 000 000 tonnes of sulphuric acid, H2804, are produced in the UK each year. use This is used in the manufacture of many important materials such as paints, fertilisers, detergents, plastics, dyestuffs and fibres. The sulphuric aCld lS prepared from sulphur in a 3 stage process. Stage 1: The sulphur is burnt in oxygen to produce sulphur dioxide. 8 + 02 —-> 802 Stage 2: The sulphur dioxide reacts with more oxygen using a catalyst to form sulphur trioxide. 2802 + 02 —-> 2803 Stage 3: The sulphur trioxide is dissolved in concentrated sulphuric acid to form ‘oleum’, H28207, which is then diluted in water to produce sulphuric acid. (a) 100 tonnes of sulphur dioxide were reacted with oxygen in stage 2. Assuming that the reaction was complete, calculate (i) how many moles of sulphur dioxnde were reacted; Mr: 802, 64.1. [1 tonne = 1 x1069] [1] (ii) the mass of sulphur trioxide that formed. Mr: 803, 80.1 [1] (b) Construct a balanced equation for the formation of sulphuric acid from oleum. ...................................................................................................................................... [1] 2811 Janet 9 For Examiners (c) The concentration of the sulphuric acid can be checked by titration. A sample of the use sulphuric acid was analysed as follows. 0 10.0 cm3 of sulphuric acid was diluted with water to make 1.00 dm3 of solution. 0 The diluted sulphuric acid was then titrated with aqueous sodium hydroxide, NaOH. HZSO4(aq) + 2NaOH(aq) ——> Na2804(aq) + 2H20(l) 0 In the titration, 25.Ocm3 of 0.100moldm“3 aqueous sodium hydroxide required 20.0 cm3 of the diluted sulphuric acnd for neutralisation. (i) Calculate how many moles of NaOH were used. [1] ii) Calculate the concentration, in mol dm‘3, of the diluted sulphuric acid, H SO . 2 4 [2] (iii) Calculate the concentration, in moldm‘3, of the original sulphuric acid sent for analysis. [1] [Total : 7] 2811 Janoi [Tu rn over I‘m: 6 1 505 10 The atomic radii of the elements Li to F and Na to Cl are shown in the table below. element Li Be B C N 0 atomic radius/hm 0.134 0.125 0.090 0.077 0.075 0.073 0.071 element Na Mg Al Si P 8 Cl atomic radius/nm 0.154 0.145 0.130 0.118 0.110 0.102 0.099 (a) Using only the elements in this table, select (i) an element with both metallic and non-metallic properties, ............................................................................................................................... [1] (ii) the element with the largest first ionisation energy, ............................................................................................................................... [1] (iii) an element with a giant molecular structure. ............................................................................................................................... [1] (b) Explain what causes the general decrease in atomic radii across each period? ...................................................................................................................................... [3] (c) Predict and explain whether a sodium ion is larger, smaller or the same size as a sodium atom. .......................................................................................................................................... .......................................................................................................................................... .......................................................................................................................................... ...................................................................................................................................... [3] [Total : 9] 2811 Jan01 1 505 11 For Examine Chlorine and its compounds have many uses. Chlorine bleach is used to kill bacteria. use (a) Chlorine bleach is made by the reaction of chlorine with aqueous sodium hydroxide. C12(g) + 2NaOH(aq) —-> NaClO(aq) + NaCl(aq) + H200) (i) Determine the oxidation number of chlorine in 012 ............................................................................................................................. NaClO ....................................................................................................................... NaCl ...................................................................................................................... [3] (ii) The actual bleaching agent is the C10‘ ion. In the presence of sunlight, this ion decomposes to release oxygen gas. Construct an equation for this reaction. ............................................................................................................................... [1] (b) The sea contains a low concentration of bromide ions. Bromine can be extracted from sea water by first concentrating the sea water and then bubbling chlorine through this solution. (i) The chlorine oxidises bromide ions to bromine. Construct a balanced ionic equation for this reaction. ............................................................ [1] (ii) Suggest how bromine could be removed from the sea water after this oxidation. ............................................................................................................................... [1] (c) Phosgene is a compound of chlorine, carbon and oxygen, used to make polyurethanes gigs/eerie has the percentage composition by mass: Cl, 71.7%; C, 12.1%; 0, 16.2%. (i) Show that the empirical formula of phosgene is ClZCO. [2] (II) The molecular formula of phosgene is the same as its empirical formula. Draw a possible structure, including bond angles, for a molecule of phosgene. [2] [Total : 10] 2311 m1 [Turn over 12 In the following question, 2 marks are available for the quality of written communication. You should use diagrams to illustrate your answer. 8 Sodium reacts with chlorine forming sodium chloride. (a) Describe the bonding in Na, Cl2 and NaCL [8] (b) Relate the physical properties of Cl2 and NaCl to their structure and bonding. [8] [Total : 16] ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... ......................................................................................................................................................... 2811 Jan01 Exa ...
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