9701_w17_qp_42
A paper of Chemistry, 9701
Questions:
8
Year:
2017
Paper:
4
Variant:
2

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The compound chlorine dioxide, Cl O2, can be prepared by the reaction shown. NaCl O2 + 1 2Cl 2 Cl O2 + NaCl Using oxidation numbers, explain why this reaction is a redox reaction. The central atom in the molecule of Cl O2 is chlorine. Draw the ‘dot-and-cross’ diagram for Cl O2. Show outer electrons only. The reaction between Cl O2 and F2 is shown. 2Cl O2 + F2 2Cl O2F The rate of the reaction was measured at various concentrations of the two reactants and the following results were obtained. experiment [Cl O2] / mol dm–3 [F2] / mol dm–3 initial rate / mol dm–3 s–1 0.010 0.060 2.20 × 10–3 0.025 0.060 to be calculated to be calculated 0.040 7.04 × 10–3 The rate equation is rate = k [Cl O2][F2]. What is meant by the term order of reaction with respect to a particular reagent? Use the results of experiment 1 to calculate the rate constant, k, for this reaction. Include the units of k. rate constant, k = units Use the data in the table to calculate ● the initial rate in experiment 2, initial rate = mol dm–3 s–1 ● [Cl O2] in experiment 3. [Cl O2] = mol dm–3 What is meant by the term rate-determining step? The equation for the reaction between Cl O2 and F2 is shown. 2Cl O2 + F2 2Cl O2F rate = k [Cl O2][F2] The mechanism for this reaction has two steps. Suggest equations for the two steps of this mechanism, stating which of the two steps is the rate-determining step. step 1 step 2 rate-determining step = By considering the rate equation, explain why the rate increases with increasing temperature.
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The arrangement of the anions around a cation is called the geometry of the cation; e.g. in [CuCl 4]2– the geometry of copper is tetrahedral and the co-ordination number of copper is 4. The geometry of a cation in an ionic compound can be predicted from the ratio of the ionic radii of the cation and anion involved. cation radius anion radius geometry of cation 0.155 – 0.225 trigonal planar 0.225 – 0.414 tetrahedral 0.414 – 0.732 octahedral Use data from the Data Booklet to predict the geometry of, and hence the co-ordination number of, the cation for ● sodium chloride, NaCl, geometry of Na+ = co-ordination number of Na+ = ● magnesium chloride, MgCl 2. geometry of Mg2+ = co-ordination number of Mg2+ = Magnesium(chloride, MgCl, is an unstable compound and readily decomposes as shown. 2MgCl Mg+ MgCl 2Use the following data to calculate the enthalpy change of this reaction. MgCl = –106 kJ mol–1 MgCl 2= – 642 kJ mol–1 enthalpy change = kJ mol–1 The equation for which ΔH is the lattice energy for MgCl is shown. Mg++ Cl –MgCl Use the equation, the following data, and relevant data from the Data Booklet to calculate a value for the lattice energy of MgCl. You might find it helpful to construct an energy cycle. electron affinity of Cl = –349 kJ mol–1 enthalpy change of atomisation of Mg= +147 kJ mol–1 enthalpy change of formation of MgCl = –106 kJ mol–1 lattice energy MgCl = kJ mol–1 Suggest how the lattice energies of MgCl 2 and NaCl will compare to that of MgCl. Explain your answers. MgCl 2 and MgCl NaCl and MgCl Define the term electron affinity.
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Calcium carbide, CaC2, reacts readily with water, forming ethyne, C2H2, and a sparingly soluble white ionic compound. Write an equation for the reaction of CaC2 with water. Draw a ‘dot-and-cross’ diagram for the carbide ion, C2 2–. Show outer electrons only. Ethyne is the simplest member of the alkyne homologous series. C ethyne H C H Propyne, C3H4, and butyne, C4H6, are the next two members of the series. Deduce the general formula for the alkynes. Ethyne can be polymerised into poly, which is a conducting polymer. C C H H polyn Suggest why this polymer conducts electricity. State the empirical formula of poly. By reference to a physical or chemical property, suggest one advantage of a conducting polymer when compared with metals. Alkynes can react with carbonyl compounds under basic conditions as shown in reaction1. C R C C small amount of base R' R'' O H C R C C reaction 1 R' OH R'' The first step of the mechanism of reaction1 involves the alkyne anion reacting with the carbonyl compound. Complete the first step of the mechanism and draw the intermediate for this reaction. Include all relevant dipoles, charges and curly arrows. C R C– C R' R'' O C R C intermediate C R' OH R'' Suggest the name of the mechanism in reaction 1. An alkyne, Q, and a carbonyl compound, R, react together to form compound P as shown. C CH2 C C C C2H5C C2H5C CH3 CH3 OH OH P 2Q + R Use reaction 1 to suggest the structures of Q and R. Q R A series of twelve separate experiments is carried out as shown in the table. Complete the table by writing in each box a tick () if a reaction occurs, or a cross ( ) if no reaction occurs. CH3CHO HCO2H CH3COCH3 HO2CCO2H hot, acidified MnO4 –alkaline I2warm Tollens’ reagent 
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