OCR ADVANCED SUBSIDIARY GCE IN CHEMISTRY (SALTERS) (3887) OCR ADVANCED GCE IN CHEMISTRY (SALTERS) (7887)

Oxford Cambridge and RSA Examinations Advanced Subsidiary GCE CHEMISTRY (SALTERS) CHEMISTRY FOR LIFE 2850 Specimen Paper Candidates answer on the question paper. Additional materials: Data Booklet for Chemistry (Salters) To be brought by candidate: electronic calculator TIME 1 hour 30 minutes INSTRUCTIONS TO CANDIDATES Write your name, Centre number and candidate number in the spaces at the top of this page. Answer all questions. Write your answers in the spaces provided on the question paper. There should be ample space for your answers. If you need more space for answers or rough work you may use the blank spaces at the end of questions or any blank pages. Rough work that is not to be marked should be crossed out. You will be awarded marks for the quality of your written communication where an answer requires a piece of extended writing. INFORMATION FOR CANDIDATES The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table and other tables of information are provided in a data booklet for use with this examination; other necessary data are given as required in the questions. You may use an electronic calculator. . Specimen Materials 4 © OCR 2000 Chemistry (Salters) Oxford, Cambridge and RSA Examinations Answer all questions. 1. Bone consists of a complex mixture of calcium salts, such as calcium carbonate, and other material. If bone is strongly heated, the calcium salts turn into calcium oxide, CaO. This can be separated from the other material by dissolving it in dilute hydrochloric acid, to form calcium chloride, CaCl2, solution. (a) (i) Draw a flow diagram to show how calcium carbonate in bone is turned into calcium chloride. Show the formulae of the compounds connected by labelled arrows. [3] (ii) Complete and balance the chemical equation for the reaction between solid calcium oxide and dilute hydrochloric acid, showing state symbols. CaO + HCl [2] (b) An experiment showed that 14.4 g of calcium oxide were made from a sample of bone of mass 50.0 g. (Ar : Ca, 40; O, 16) Calculate: (i) the amount in moles of CaO in 14.4 g; [2] Specimen Materials 5 © OCR 2000 Chemistry (Salters) Oxford, Cambridge and RSA Examinations (ii) the amount in moles of Ca in the bone sample; [1] (iii) the % of calcium by mass in the bone. [2] (c) Strontium compounds are incorporated into bones because their chemistry is similar to that of calcium compounds. For example, both strontium and calcium form ions with the same charge. Explain, in terms of the Periodic Table, the electronic structures of the atoms and ionisation energies, why calcium and strontium (and their compounds) have similar chemical properties. ( Note: In this question, 1 mark is available for the quality of written communication). .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... .................................................................................................................................................... ..................................................................................……………………………………… [6] Specimen Materials 6 © OCR 2000 Chemistry (Salters) Oxford, Cambridge and RSA Examinations (d) Strontium-90, 90 38 Sr, is a radioactive isotope of strontium that emits – particles (electrons). It was produced in nuclear fall-out and became incorporated in peoples’ bones. (i) For the strontium-90 nucleus, write down the number of protons ........................................................................................................... [1] neutrons ......................................................................................................... [1] (ii) Write a nuclear equation for the process by which a strontium-90 nucleus emits a – particle, representing the – particle as 10 e. [3] (iii) A sample of naturally-occurring strontium was placed in a mass spectrometer and the following peaks were obtained: Mass Intensity (%) 84 0.56 86 9.86 87 7.02 88 82.56 Calculate the relative atomic mass of the sample of strontium, giving your answer to three significant figures. Show your working