9701_w11_qp_23
A paper of Chemistry, 9701
Questions:
5
Year:
2011
Paper:
2
Variant:
3
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Examiner s Use Sulfur, S, and polonium, Po, are both elements in Group VI of the Periodic Table. Sulfur has three isotopes. Explain the meaning of the term isotope. A sample of sulfur has the following isotopic composition by mass. isotope mass % by mass 95.00 0.77 4.23 Calculate the relative atomic mass, Ar, of sulfur to two decimal places. Ar = Isotopes of polonium, proton number 84, are produced by the radioactive decay of several elements including thorium, Th, proton number 90. The isotope 213Po is produced from the thorium isotope 232Th. Complete the table below to show the atomic structures of the isotopes 213Po and 232Th. number of isotope protons neutrons electrons 213Po 232Th For Examiner’s Use Radiochemical reactions, such as nuclear fission and radioactive decay of isotopes, can be represented by equations in which the nucleon numbers must balance and the proton numbers must also balance. For example, the nuclear fission of uranium-235, 235 92U, by collision with a neutron, 1 0n, produces strontium-90, xenon-143 and three neutrons. 92U + 1 0n 38Sr + 143 54Xe + 3 0n In this equation, the nucleon numbers balance because: 235 + 1 = 90 + 143 + (3x1). The proton numbers also balance because: 92 + 0 = 38 + 54 + (3x0). In the first stage of the radioactive decay of 90 Th, the products are an isotope of element E and an alpha-particle, 4 2 He. By considering nucleon and proton numbers only, construct a balanced equation for the formation of the isotope of E in this reaction. 90Th + 4 2 He Show clearly the nucleon number and proton number of the isotope of E. nucleon number of the isotope of E proton number of the isotope of E Hence state the symbol of the element E.
1. Atomic structure  →  1.2. Isotopes
1. Atomic structure  →  1.1. Particles in the atom and atomic radius
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For Examiner’s Use When 0.42 g of a gaseous hydrocarbon A is slowly passed over a large quantity of heated copper(oxide, CuO, A is completely oxidised. The products are collected and it is found that 1.32 g of CO2 and 0.54 g of H2O are formed. Copper is the only other product of the reaction. Calculate the mass of carbon present in 1.32 g of CO2. Use this value to calculate the amount, in moles, of carbon atoms present in 0.42 g of A. Calculate the mass of hydrogen present in 0.54 g of H2O. Use this value to calculate the amount, in moles, of hydrogen atoms present in 0.42 g of A. It is thought that A is an alkene rather than an alkane. Use your answers to and to deduce whether this is correct. Explain your answer. For Examiner’s Use Analysis of another organic compound, B, gave the following composition by mass: C, 64.86%; H, 13.50%, O, 21.64%. Use these values to calculate the empirical formula of B. The empirical and molecular formulae of B are the same. B is found to be chiral. Draw displayed formulae of the two optical isomers of this compound, indicating with an asterisk (*) the chiral carbon atom. There are three other structural isomers of B which are not chiral but which contain the same functional group as B. In the boxes below, draw the structural formulae of these isomers.
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
14. Hydrocarbons  →  14.2. Alkenes
13. An introduction to AS Level organic chemistry  →  13.4. Isomerism: structural isomerism and stereoisomerism
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For Examiner’s Use The Periodic Table we currently use is derived directly from that proposed in 1869 by Mendeleev who had noticed patterns in the physical and chemical properties of the elements he had studied. The diagram below shows the first ionisation energies of the first 18 elements of the Periodic Table. first ionisation energy / kJ mol–1 0 1 2 3 4 5 6 7 8 9 proton number 10 11 12 13 14 15 16 17 18 H He Ne Na Ar Li Give the equation, including state symbols, for the first ionisation energy of carbon. Explain why sodium has a lower first ionisation energy than magnesium. Explain why magnesium has a higher first ionisation energy than aluminium. Explain why helium, He, and neon, Ne, occupy the two highest positions on the diagram. Explain why the first ionisation energy of argon, Ar, is lower than that of neon, which is lower than that of helium. For Examiner’s Use The first ionisation energies of the elements Na to Ar show a variation. Some physical properties show similar variations. The atomic radius of the elements decreases from Na to Cl. Give a brief explanation of this variation. The cations formed by the elements Na to Al are smaller than the corresponding atoms. Give a brief explanation of this change. The oxides of the elements of the third Period behave differently with NaOHand HCl . In some cases, no reaction occurs. Complete the table below by writing a balanced equation for any reaction that occurs, with heating if necessary. If you think no reaction takes place write ‘no reaction’. You do not need to include state symbols in your answers. MgO+ NaOH MgO+ HCl Al2O3+ NaOH + H2O Al2O3+ HCl SO2+ NaOH SO2+ HCl
1. Atomic structure  →  1.4. Ionisation energy
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For Examiner’s Use The structural formulae of six different compounds, P – U, are given below. CH3CH=CHCH2CH3 CH3CH2COCH2CH3 CH2=CHCH2CH2CH3 P Q R CH3CH2CH2CH2CH2OH HOCH2CH2CH(OH)CH3 CH3CH2CH2OCH2CH3 S T U What is the empirical formula of compound T? Draw the skeletal formula of compound S. Compounds S and U are isomers. What type of isomerism do they show? Two of the six formulae P – U can each be drawn in two forms which are known as stereoisomers. Which two compounds have formulae that can be drawn in two forms? What type of stereoisomerism does each show? Identify each compound by its letter. compound type of stereoisomerism For Examiner’s Use Compound S can be converted into compound R. What type of reaction is this? What reagent would you use for this reaction? Write the structural formula of the compound formed when T undergoes the same reaction using an excess of the reagent you have used in . Compound P may be converted into compound Q in a two-step reaction. CH3CH=CHCH2CH3 step 1 intermediate step 2 CH3CH2COCH2CH3 P Q What is the structural formula of the intermediate compound formed in this sequence? Outline how step 1 may be carried out to give this intermediate compound. What reagent would be used for step 2?
13. An introduction to AS Level organic chemistry  →  13.4. Isomerism: structural isomerism and stereoisomerism
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
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For Examiner’s Use Each of the three organic compounds, V, W, and X, has the empirical formula CH2O. The number of carbon atoms in each of their molecules is shown in the table. compound number of C atoms V W X V gives a brick red precipitate when warmed with Fehling’s reagent; W and X do not. W is a fruity smelling liquid. In X, the carbon atoms are bonded directly to one another. X gives an effervescence when shaken with Na2CO3; V and W do not. Give the structural formula of V. What functional group is present in W? Give the structural formula of W. When X is heated under reflux with acidified K2Cr2O7, the product, Y, gives no reaction with 2,4-dinitrophenylhydrazine reagent. Give the structural formula of X. Give the structural formula of Y, the compound formed from X. For Examiner’s Use When X is warmed with a little concentrated sulfuric acid, a small amount of a cyclic compound, Z, is formed. Z has the molecular formula C6H8O4. Suggest a displayed formula for Z. What type of reaction occurs when Z is formed from X?
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
21. Organic synthesis  →  21.1. Organic synthesis
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