9701_w17_qp_42
A paper of Chemistry, 9701
Questions:
8
Year:
2017
Paper:
4
Variant:
2
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1
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.
11. Group 17  →  11.4. The reactions of chlorine
8. Reaction kinetics  →  8.1. Rate of reaction
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When water is added to magnesium nitride, Mg3N2, the products are a white suspension of Mg(OH)2 and an alkaline gas. Write an equation for this reaction. A 2.52 g sample of Mg3N2 is added to an excess of water. Calculate the mass of Mg(OH)2 formed. mass of Mg(OH)2 = g State and explain how the solubility of the Group2 hydroxides varies down the group. Magnesiumhydroxide is sparingly soluble in water. The concentration of its saturated solution at 298 K is 1.7 × 10–4 mol dm–3. Write an expression for the solubility product, Ksp, of Mg(OH)2. Ksp = Calculate the value of Ksp for Mg(OH)2 at 298 K and state its units. Ksp = units The temperature at which the Group2 hydroxides and carbonates start to decompose increases down the group. Suggest an explanation for this trend in the decomposition temperature of the Group 2 hydroxides.
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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Serotonin can be synthesised from the amino acid tryptophan in two steps. NH2 CO2H N H NH2 CO2H N H tryptophan serotonin HO NH2 N H HO In a buffer solution at pH 5.9, a sample of tryptophan does not move during electrophoresis. Draw the structures of the ions formed by tryptophan at pH 1.0 and pH 5.9. pH 1.0 pH 5.9 Tryptophan can combine with valine to form a dipeptide. Use the Data Booklet to draw the structure of this dipeptide. Complete the following table to show the structures of the products formed and the typeofreaction occurring when serotonin reacts with the four reagents in separate reactions. reagent structure of product type of reaction Na excess Br2excess CH3COCl excess H2 / Pt catalyst Serotonin is converted by enzymes in the liver to compound M. serotonin NH2 N H HO M OH N H HO enzymes O By reference to the Data Booklet, suggest how the infra-red spectrum of M would differ from that of serotonin. The proton NMR spectrum of M dissolved in CDCl 3 shows eight peaks due to the eight different types of proton present in the molecule. The proton NMR spectrum of M dissolved in D2O was recorded. Predict the number of peaks that would be seen in the proton NMR spectrum of M in D2O. Explain your answer. number of peaks explanation Compound M can be polymerised under certain conditions to form polymer N, shown. N H O O N Polymer N is biodegradable, unlike polyethene which is not. Explain why N is biodegradable.
17. Carbonyl compounds  →  17.1. Aldehydes and ketones
14. Hydrocarbons  →  14.2. Alkenes
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An electrochemical cell consists of a half-cell containing V3+and V2+ions and another half‑cell containing VO2 +and VO2+ions. Use data from the Data Booklet to calculate a value for the . = V Write the ionic equation for the cell reaction. Draw a fully labelled diagram of the apparatus you could use to measure the potential of this cell. Include the necessary chemicals. Use data from the Data Booklet to predict whether a reaction might take place when the following pairs of aqueous solutions are mixed. If a reaction occurs, write an equation for it and calculate the . ● V2+and Sn4+Does a reaction occur? equation ● VO2+and Fe3+Does a reaction occur? equation
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
11. Group 17  →  11.4. The reactions of chlorine
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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.
4. States of matter  →  4.2. Bonding and structure
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
3. Chemical bonding  →  3.2. Ionic bonding
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Define the term transition metal complex. Platinum can form the compound [Pt(NH3)4Cl 2][PtCl 4]. State the co-ordination numbers and the oxidation numbers of the platinum in the two ions of this compound. co-ordination number oxidation number [Pt(NH3)4Cl 2]2+ [PtCl 4]2– Draw three-dimensional diagrams to show the structures of the two isomers of [Pt(NH3)4Cl 2]2+. Solutions of the compounds [Pt(NH3)4Cl 2]Br2 and [Pt(NH3)4Br2]Cl 2 can be distinguished from each other by a simple chemical test. Assume that any species bonded to the platinum ion does not react in this test. Complete the table with a test that could be used to positively identify each compound. Give details of expected observations with each compound. test observation with [Pt(NH3)4Cl 2]Br2 observation with [Pt(NH3)4Br2]Cl 2 In this question you should consider geometrical and optical isomerism. What type of isomerism is shown by the following complexes? You should answer geometrical, optical, both or neither. octahedral [Co(NH2CH2CH2NH2)2Cl 2]+ square planar [Ni(CN)2Cl 2]2– tetrahedral [CuBr2Cl 2]2–  Many enzymes contain transition metal complexes. Describe, with the aid of a suitably labelled diagram, how an enzyme catalyses the breakdown of a substrate molecule.
14. Hydrocarbons  →  14.2. Alkenes
14. Hydrocarbons  →  14.1. Alkanes
8. Reaction kinetics  →  8.3. Homogeneous and heterogeneous catalysts
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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 
14. Hydrocarbons  →  14.2. Alkenes
14. Hydrocarbons  →  14.1. Alkanes
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Compound A can be produced from a plant hormone. A O HO O OH Compound A shows optical and geometrical isomerism. On the structure of A above, ● draw a line through the bondthat give rise to geometrical isomerism, ● circle all chiral carbon atoms. Give the names of four functional groups present in A. A molecule of A has 17 carbon atoms. State the number of carbon atoms that are sp, sp2 and sp3 hybridised in A. sp carbons = sp2 carbons = sp3 carbons = When A is reacted with an excess of hot, concentrated manganate(ions, a mixture of three organic compounds is formed. A X and Y and Z (C10H14O7) (C3H4O3) (C4H6O3) Suggest the structures of Y and Z. Y (C3H4O3) Z (C4H6O3) A mixture of three different compounds, J, K and L, was analysed by thinlayer chromatography using a polar stationary phase and a non-polar mobile phase. The three compounds all have similar molecular masses. The resulting chromatogram is shown. solvent front mixture Identify which spot corresponds to each compound. compound spot J CH3COCO2H K HO2CCO2H L CH3CH2COCH2CH3 Explain your answers to . What is meant by the term Rf value?
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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