9701_s05_qp_2
A paper of Chemistry, 9701
Questions:
5
Year:
2005
Paper:
2
Variant:
0
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1
Iron and cobalt are adjacent elements in the Periodic Table. Iron has three main naturally occurring isotopes, cobalt has one. Explain the meaning of the term isotope. The most common isotope of iron is 56Fe; the only naturally occurring isotope of cobalt is 59Co. Use the Data Booklet to complete the table below to show the atomic structure of 56Fe and of 59Co. A sample of iron has the following isotopic composition by mass. Define the term relative atomic mass. By using the data above, calculate the relative atomic mass of iron to three significant figures. Examiner s Use isotope isotope mass 5.84 91.68 2.17 % by mass protons number of neutrons electrons 56Fe 59Co
1. Atomic structure  →  1.2. Isotopes
2. Atoms, molecules and stoichiometry  →  2.1. Relative masses of atoms and molecules
22. Analytical techniques  →  22.2. Mass spectrometry
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2
Sulphur and its compounds are found in volcanoes, in organic matter and in minerals. Sulphuric acid, an important industrial chemical, is manufactured from sulphur by the Contact process. There are three consecutive reactions in the Contact process which are essential. Write a balanced equation (using where appropriate) for each of these reactions in the correct sequence. What catalyst is used? Hydrogen sulphide, H2S, is a foul-smelling compound found in the gases from volcanoes. Hydrogen sulphide is covalent, melting at –85 °C and boiling at –60 °C. Draw a ‘dot-and-cross’ diagram to show the structure of the H2S molecule. Predict the shape of the H2S molecule. Oxygen and sulphur are both in Group VI of the Periodic Table. Suggest why the melting and boiling points of water, H2O, are much higher than those of H2S. For Examiner’s Use Hydrogen sulphide burns with a blue flame in an excess of oxygen to form sulphur dioxide and water. Write a balanced equation for the complete combustion of H2S. What is the change in the oxidation number of sulphur in this reaction? from to What volume of oxygen, measured at room temperature and pressure, is required for the complete combustion of 8.65 g of H2S? Give your answer to two decimal places. Hydrogen sulphide is a weak diprotic acid. Its solution in water contains HS– and a few S2– ions. What is meant by the term weak acid? Write an equation, with state symbols, for the first ionisation of H2S when it dissolves in water. For Examiner’s Use
12. Nitrogen and sulfur  →  12.1. Nitrogen and sulfur
11. Group 17  →  11.4. The reactions of chlorine
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3
Magnesium is the eighth most common element in the Earth’s crust. The metal is widely used in alloys which are light and strong. Some reactions of magnesium and its compounds are shown in the reaction scheme below. Identify, by name or formula, compounds A to F. A B C D E F For Examiner’s Use H2+ ACdil. H2SO4 Na2CO3heat in air heat NaOHdil. HNO3 heat MgDFdil. HCl heat evaporate BEF+ H2Construct balanced equations for the following reactions. magnesium to compound A compound C to compound D compound F to compound D Suggest a balanced equation for the effect of heat on compound E. For Examiner’s Use
10. Group 2  →  10.1. Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
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4
Compound G, in which R– represents the rest of the molecule, was made for use as a tear gas in World War 2. Compound G was made by the following sequence of reactions. stage I stage II stage III R–CH3 R–CH2Cl R–CH2CN R–CHBrCN For stage I and for stage II, state the reagentand conditionused to carry out each change. stage I reagentconditionstage II reagentconditionSuggest the reagentand conditionnecessary to carry out stage III. reagentcondition R H C Br CN compound G For Examiner’s Use Compound G was not actually used in World War 2 and stocks of it had to be destroyed safely. The following sequence of reactions was used in this process. stage IV stage V R–CHBrCN R–CHBrCO2H R–CH(OH)CO2H stage VI R–CH2CO2H For stage IV and for stage V state the reagentand conditionnecessary to bring about each reaction. stage IV reagentconditionstage V reagentconditionThe full sequence of stages I to VI involves some compounds which contain chiral centres. Explain what is meant by the term chiral centre. Draw displayed formulae for the isomers of one compound in the full sequence of stages I to VI which you consider to be chiral. For Examiner’s Use
13. An introduction to AS Level organic chemistry  →  13.4. Isomerism: structural isomerism and stereoisomerism
14. Hydrocarbons  →  14.2. Alkenes
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5
A student obtained the following results when analysing an organic compound, H. The student allowed test 5 to go to completion and then investigated the product of test 5 with the following result. Calculate the molecular formula of H. What can be deduced about the nature of H by the following tests? test 3 test 4 What functional group would have given a positive result in test 6? What functional group is shown to be present in H by tests 5 and 6? For Examiner’s Use test observation test 1 test 2 test 3 test 4 test 5 test 6 relative molecular mass C, 66.7%; H, 11.1%; O, 22.2% Br2 decolourised H2evolved green colour observed no reaction % composition by mass reactions with Br2reaction with Nareaction with warm Cr2O7 2–/H+ reaction with 2,4-dinitrophenylhydrazine For Examiner’s Use On testing a sample of H, the student found that it was not chiral. H did, however, show cis-trans isomerism. How does cis-trans isomerism arise in an organic molecule? Use all of the information above to draw labelled, displayed formulae of the stereoisomers of compound H.
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
13. An introduction to AS Level organic chemistry  →  13.4. Isomerism: structural isomerism and stereoisomerism
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