9701_w05_qp_4
A paper of Chemistry, 9701
Questions:
5
Year:
2005
Paper:
4
Variant:
0
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1
Silver bromide, AgBr, is widely used in photography. In a photographic film, AgBr crystals are precipitated into a gelatine base as ‘grains’ of diameter about 1 × 10–6m. Calculate the approximate number of silver ions contained in a grain of AgBr of mass 2.5 × 10–12g. AgBr is only sparingly soluble in water. The [Ag+] in a saturated solution of AgBr can be estimated by measuring the Ecell of the following cell. In the spaces below, identify what the four letters A – D in the above diagram represent. A C B D Predict how the potential of the right hand electrode might vary as [Ag+] is decreased. In its saturated solution, [AgBr] = 7.1 × 10–7mol dm–3. Write an expression for the solubility product of AgBr, and calculate its value, including units. salt bridge H2, 1 atm, 298 K [Ag+] = x mol dm–3 A B C D Use Write a chemical equation representing the lattice energy of AgBr. Use the following data to calculate a value for the lattice energy of AgBr. first ionisation energy of silver = +731 kJ mol–1 electron affinity of bromine = –325 kJ mol–1 enthalpy change of atomisation of silver = +285 kJ mol–1 enthalpy change of atomisation of bromine = +112 kJ mol–1 enthalpy change of formation of AgBr= –100 kJ mol–1 How might the lattice energy of AgCl compare to that of AgBr? Explain your answer. In photography a bromide ion absorbs a photon and releases an electron which reduces a silver ion to a silver atom. Br– →Br + e– Ag+ + e– →Ag Predict whether it would require more energy or less energy to initiate this process in a AgCl emulsion, compared to a AgBr emulsion. Explain your answer. 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
11. Group 17  →  11.3. Some reactions of the halide ions
1. Atomic structure  →  1.4. Ionisation energy
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2
What do you understand by the term standard electrode potential? By reference to relevant E data in the Data Booklet, explain how the halogen/halide electrode potentials relate to the relative reactivity of the halogens as oxidising agents. Use data from the Data Booklet to construct redox equations, and calculate the standard cell potentials, for the reactions between Acidified H2O2and KI, Cl2+ SO2. Use data from the Data Booklet to predict the likely product of the reaction between I2and tin metal, writing a balanced equation for the reaction. Use
11. Group 17  →  11.2. The chemical properties of the halogen elements and the hydrogen halides
11. Group 17  →  11.3. Some reactions of the halide ions
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3
Use the following sets of axes to sketch graphs of the variations in the melting points and the electrical conductivities of the Group IV elements. Explain how the variation in conductivity is related to the structure and bonding in the elements. Going down Group IV there is a variation in the relative stabilities of the higher and lower oxidation states of the elements in their oxides. Illustrating your answers with balanced chemical equations, in each of the following cases suggest one piece of chemical evidence to show that CO is less stable than CO2, PbO is more stable than PbO2. C low medium high melting point electric conductivity Si Ge Sn Pb C low medium high Si Ge Sn Pb Use Name one ceramic based on silicon(oxide, and explain what properties of the oxide make it suitable for this use. Tin(oxide reacts with both acids and alkalis. What name is given to this property of an oxide? Write suitable equations to show these two reactions of tin(oxide. Examiner’s Use
9. The Periodic Table: chemical periodicity  →  9.1. Periodicity of physical properties of the elements in Period 3
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
Rodinol is used as a photographic developer. In alkaline solution it is a mild reducing agent, providing electrons according to the following half equation. Rodinol ‘develops’ a latent photographic image by reducing activated silver bromide grains to silver metal and bromide ions. Construct a balanced equation for the reaction between rodinol and AgBr. Suggest, with a reason, how the basicity of rodinol might compare to that of ammonia. Suggest structural formulae for the compounds E, F and G in the following chart of the reactions of rodinol. NH2 rodinol OH E F G HCl NaOH Br2NH2 rodinol OH O O 2 OH– + + + + H2O NH3 2e– Use E = +0.65 V Rodinol can be synthesised from phenol by the following route. Suggest reagents and conditions for step I. What type of reaction is step II? Place a tick in the box by the most suitable reagent for step II. (place a tick in one box only) H3O+ + heat OH–+ heat Cr2O7 2– + H+ + heat HNO3Sn + HClNH3 in ethanol + heat/pressure Rodinol is also an important intermediate in the commercial production of the analgesic drug paracetamol. Name two functional groups in paracetamol. Suggest a reagent to convert rodinol into paracetamol. OH NH2 OH paracetamol NHCOCH3 OH NO2 OH OH NH2 I II Examiner’s Use
16. Hydroxy compounds  →  16.1. Alcohols
15. Halogen compounds  →  15.1. Halogenoalkanes
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5
Hydrophilic polymers find important uses in the manufacture of contact lenses and wound dressings. Their chemical structures allow them to bond with water molecules, which keeps them soft and flexible. Sections of two hydrophilic polymers are shown below. What type of polymerisation has produced polymer H? polymer J? What type of attractions might occur between these polymers and molecules of water? Chains of polymer H can be ‘cross-linked’, i.e. joined together, by reaction with a small bifunctional molecule. Which one of the following molecules would be most suitable for such cross- linking? (place a tick in one box only) HOCH2CH2OH H2NCH2CH2NH2 HOCH2CH2CO2H HO2CCH2CH2CO2H H2NCH2CH2CO2H What type of bond would be formed during the cross-linking? OH CH C C C C O O H2 OH CH C H2 OH CH C H2 H H J N H H2 H2 N H N OH OH OH CH CH CH C OH CH C H2 Use Examiner’s Use Suggest the reagents and conditions needed to hydrolyse polymer J into its monomers. Draw the structural formulae of the two products of this hydrolysis reaction. The last compound in the list in above is 3-aminopropanoic acid. This can be made from potassium chloroethanoate by the following 3-stage route. In the box above write the structure of the intermediate in this route. Suggest reagents and conditions for stage II stage III ClCH2CO2– K+ H2NCH2CH2CO2– K+ H2NCH2CH2CO2H KCN stage II stage III
20. Polymerisation  →  20.1. Addition polymerisation
14. Hydrocarbons  →  14.2. Alkenes
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