9701_w14_qp_42
A paper of Chemistry, 9701
Questions:
8
Year:
2014
Paper:
4
Variant:
2
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1
The oxidation of nitrogen(oxide is shown in the equation. 2NO+ O2→ 2NO2The initial rate of this reaction was measured, starting with different concentrations of the two reactants. The following results were obtained. experiment number [NO] / mol dm–3 [O2] / mol dm–3 initial rate / mol dm–3 s–1 0.032 0.012 4.08 × 10–3 0.032 0.024 8.15 × 10–3 0.064 0.024 3.28 × 10–2 0.096 0.036 Use the data in the table to determine the order with respect to each reactant. Show your reasoning. Calculate the initial rate in experiment 4. Give your answer to two signifi cant fi gures. initial rate = mol dm–3 s–1 Write the rate equation for this reaction. Use the results of experiment 1 to calculate the rate constant, k, for this reaction. Include the units of k. rate constant, k = units On the following axes ● draw two Boltzmann distribution curves, at two different temperatures, T1 and T2 (T2 > T1), ● label the curves and the axes. State and explain, using your diagram, the effect of increasing temperature on the rate of reaction. The compound nitrosyl fl uoride, NOF, can be formed by the following reaction. 2NO+ F22NOFThe rate is fi rst order with respect to NO and F2. The reaction mechanism has two steps. Suggest equations for the two steps of this mechanism, stating which is the rate determining slower step.
8. Reaction kinetics  →  8.1. Rate of reaction
8. Reaction kinetics  →  8.2. Effect of temperature on reaction rates and the concept of activation energy
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2
Complete the electron confi gurations for Ni and Ni2+. 3d 4s Ni [Ar] Ni2+ [Ar] The presence of electrons in d orbitals is responsible for the colours of transition element compounds. The d orbitals in an isolated transition metal atom or ion are all at the same energy level. What term is used to describe orbitals that are at the same energy level? Complete the diagram to show the splitting of the d orbital energy levels in an octahedral complex ion. energy On the axes below, sketch the shapes of one d orbital from the lower energy level and one d orbital from the higher energy level. y lower energy level z x y z x higher energy level The octahedral complex [Ni(H2O)6]2+ is green. Explain the origin of the colour of this complex. When NH3is added to the green solution containing [Ni(H2O)6]2+, a grey-green precipitate, A, is formed. This precipitate dissolves in an excess of NH3to give a blue-violet solution, B. Suggest formulae for A and B and write equations for the two reactions producing A and B.
1. Atomic structure  →  1.3. Electrons, energy levels and atomic orbitals
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3
Natural phosphorus consists of one isotope, 31P. Chlorine exists naturally as two isotopes, 35Cl and 37Cl, in the relative abundance ratio of 3 : 1. The mass spectrum of PCl 3 contains several peaks corresponding to a number of molecular fragments. Suggest the isotopic composition of the fragments with the following mass numbers. mass number isotopic composition Predict the relative ratios of the peak heights of the three peaks corresponding to these fragments. Phosphorus reacts with chlorine to form a variety of chlorides. PCl 5 is an example of a compound that exists as two structures depending on the conditions. 2PCl 5[PCl 4]+[PCl 6]–Draw a ‘dot-and-cross’ diagram to show the bonding in PCl 5. Show the outer electrons only. Draw diagrams to suggest the shapes of [PCl 4]+ and [PCl 6]–. [PCl 4]+ [PCl 6]– Phosphorus(oxide, P4O6, contains no P–P or O–O bonds. In the P4O6 molecule, all oxygen atoms are divalent and all phosphorus atoms are trivalent. Sketch a structure for P4O6. P4O6 can act as a ligand. What is meant by the term ligand ? Phosphate ions in water can be removed by adding a solution containing Ca2+ions, which form a precipitate of calcium phosphate, Ca3(PO4)2. Write an expression for the Ksp of Ca3(PO4)2. Ksp = The solubility of Ca3(PO4)2 is 2.50 × 10–6 mol dm–3 at 298 K. Calculate the solubility product, Ksp, of Ca3(PO4)2 at this temperature. Include the units. Ksp = units What is meant by the term lattice energy? Explain why the lattice energy of calcium phosphate is less exothermic than that of magnesium phosphate.
9. The Periodic Table: chemical periodicity  →  9.2. Periodicity of chemical properties of the elements in Period 3
11. Group 17  →  11.4. The reactions of chlorine
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4
Methylbenzene undergoes electrophilic substitution with nitronium ions, NO2 +. Nitronium ions are generated by the reaction between concentrated sulfuric acid and concentrated nitric acid. Construct an equation for the formation of nitronium ions, NO2 +, by this method. Complete the scheme to show the mechanism for this reaction. Use curly arrows to show the movement of electron pairs. CH3 NO2 + Describe and explain the relative acidities of chloroethanoic acid and ethanoic acid. Describe and explain the relative acidities of phenol and ethanol. Phenyl 2-hydroxybenzoate is an antiseptic. OH O O phenyl 2-hydroxybenzoate Complete the following table about the reactions of phenyl 2-hydroxybenzoate with the three reagents. reagent structure of producttype of reaction Na excess Br2excess hot NaOH
11. Group 17  →  11.3. Some reactions of the halide ions
14. Hydrocarbons  →  14.2. Alkenes
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5
Organohalogen compounds can undergo hydrolysis. R–Cl + H2O → R–OH + HCl State the relative rates of hydrolysis of the following compounds. CH3CH2CH2Cl CH3CH2COCl C6H5Cl Explain your answer. Aminolaevulinic acid is involved in the synthesis of haemoglobin and chlorophyll. OH O O H2N aminolaevulinic acid Name the three functional groups in aminolaevulinic acid. Aminolaevulinic acid reacts readily with bromoethane. Show the mechanism of the fi rst step of this reaction on the diagram. Include all necessary curly arrows, lone pairs and relevant dipoles. OH O O H2N OH O O HN H3C H3C CH2 Br intermediate Name the mechanism in . Identify the non-organic product formed in this reaction. Three reactions of aminolaevulinic acid are shown. Draw the structures of the products W, X and Y in the boxes below. OH O O H2N CH3COCl NaBH4 HCl , warm W X Y aminolaevulinic acid Aminolaevulinic acid can undergo polymerisation. Draw the structure of the polymer showing two repeat units. The linkages between the monomer units should be shown fully displayed.
13. An introduction to AS Level organic chemistry  →  13.2. Characteristic organic reactions
14. Hydrocarbons  →  14.2. Alkenes
21. Organic synthesis  →  21.1. Organic synthesis
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6
A mixture of amino acids can be separated by electrophoresis. During an electrophoresis experiment, ● different amino acids move in different directions, ● different amino acids move at different speeds, ● some amino acids do not move at all. Explain these observations. A mixture of amino acids can also be separated by thin-layer chromatography. Identify the mobile and the stationary phases in this type of chromatography. mobile phase stationary phase What is the process by which thin-layer chromatography can separate a mixture? State three structural features of DNA. Some diseases are caused by a mutation in the DNA base sequence which results in one amino acid being replaced by another during protein synthesis. Suggest what changes in the interactions that form the tertiary structure would result from a mutation that replaced a valine residue with a serine residue. CH3 CH3 CH C HC val NH O OH CH2 CH C ser NH O replaced by
14. Hydrocarbons  →  14.2. Alkenes
7. Equilibria  →  7.2. Brønsted–Lowry theory of acids and bases
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7
Oseltamivir is an antiviral drug that slows the spread of the infl uenza (fl u) virus. O HN O O O NH2 oseltamivir Circle two bonds, each in a different functional group, that could be easily hydrolysed in the body. Oseltamivir is a chiral drug. This drug is usually taken as a single optical isomer rather than as a mixture of isomers. Suggest one benefi t of taking a drug in this way. Oseltamivir is a competitive inhibitor of an enzyme produced by the fl u virus. Explain the meaning of the term competitive inhibitor and state how its action could be overcome. ATP plays an important role in metabolic reactions in living organisms. NH2 N N N CH2O P H H N H O HO H OH O P O P O– O– O– O O O O– ATP What is the function of ATP in living organisms?
11. Group 17  →  11.4. The reactions of chlorine
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8
T is a saturated alcohol. It was analysed by mass spectroscopy and NMR spectroscopy. In the mass spectrum, the molecular ion peak, M, was at an m/e value of 74 and the ratio of the heights of the M and M+1 peaks was 20.4 : 0.9. Use the ratio of the heights of the M and M+1 peaks to calculate the number of carbon atoms in a molecule of T. What is the molecular formula of T? molecular formula = The NMR spectrum of T given below shows four absorptions. The absorption at 1.8 ppm is a multiplet and that at 2.5 ppm is a singlet. δ / ppm Use this information and your answer to to deduce the structure of T. T Describe and explain which type of proton is responsible for each of the absorptions. The absorption at 1.8 ppm is a multiplet and that at 2.5 is a singlet. State and explain the splitting patterns of the other absorptions, at 0.9 and 3.4 ppm. Describe and explain how the NMR spectrum of T dissolved in D2O would differ from the one shown.
22. Analytical techniques  →  22.2. Mass spectrometry
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
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