9701_w15_qp_41
A paper of Chemistry, 9701
Questions:
10
Year:
2015
Paper:
4
Variant:
1
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1
Calcium has atomic number 20. Complete the electronic structures for a calcium atom, 1s22s22p6 calcium ion in the +2 oxidation state. 1s22s22p6 Calcium nitrate, Ca(NO3)2, is used in fertilisers and can be prepared by an acid-base reaction. Write an equation for the preparation of calcium nitrate by an acid-base reaction. When anhydrous calcium nitrate is heated strongly, it decomposes to leave a white solid. Identify this white solid and suggest another observation for this reaction. The ease of thermal decomposition of the Group II nitrates decreases down the group. Explain this trend. What is meant by the term standard enthalpy change of hydration, ? Use the following data to calculate the lattice energy, , of calcium nitrate, Ca(NO3)2. You may find it helpful to construct an energy cycle. enthalpy change value (Ca2+) –1650 kJ mol–1 (NO3 –) –314 kJ mol–1 enthalpy change of solution for Ca(NO3)2–19 kJ mol–1 Ca(NO3)2= kJ mol–1 The standard enthalpy change of hydration for Ba2+, (Ba2+), is –1305 kJ mol–1. Suggest an explanation for why the of the Ba2+ ion is less exothermic than the of the Ca2+ ion.
12. Nitrogen and sulfur  →  12.1. Nitrogen and sulfur
10. Group 2  →  10.1. Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
5. Chemical energetics  →  5.1. Enthalpy change, \(\Delta H\)
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Complete the table to show the number of unpaired electrons in the outer shell of each of the gaseous atoms, Na to Ar. Na Mg Al Si P S Cl Ar number of unpaired electrons Complete the table for the reactions of two Period 3 chlorides with water. Period 3 chloride observations pH of solution formed SiCl 4 PCl 5 Write an equation for the reaction between SiCl 4 and H2O.
9. The Periodic Table: chemical periodicity  →  9.2. Periodicity of chemical properties of the elements in Period 3
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The transition element iron is the most abundant element in the Earth’s core. What is meant by the term transition element? In aqueous solution, iron can form complex ions which contain ligands. Name the type of bonding that occurs between a ligand and a transition element. Which of the following species can act as a ligand? Complete the table by placing a tick () in the appropriate column to indicate whether the species can act as a ligand or not. species can act as a ligand cannot act as a ligand NO3 – BF3 H2NCH2CH2NH2 NH4 + Manganese ions, Mn2+, show some similar chemical properties to those of copper(ions, Cu2+. Use this information and the Data Booklet to suggest the formula of the manganese species formed in each of the following reactions. State the type of reaction taking place in each case. formula of manganese species formed type of reaction Mn2++ NaOHMn2++ concentrated HCl Mn2++ H2O2
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
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In aqueous solution, 2-chloro-2-methylpropane, (CH3)3CCl, reacts with sodium hydroxide, NaOH. This is a nucleophilic substitution reaction. (CH3)3CCl + NaOH→ (CH3)3COH+ NaCl Show the mechanism for this reaction. Include all necessary curly arrows, lone pairs and relevant dipoles. The rate of this reaction was investigated using a large excess of sodium hydroxide. The graph below shows the results of the experiment. 0.60 0.50 0.40 0.30 0.20 0.10 time / s [(CH3)3CCl ] / mol dm–3 The reaction is first order with respect to [(CH3)3CCl ]. This can be confirmed from the graph using half-lives. What is meant by the half-life of a reaction? Calculate the half-life for this reaction. Show all your working and show clearly any construction lines on the graph. What would be the effect on the half-life of this reaction if the initial concentration of [(CH3)3CCl ] was doubled? Use the graph in to determine the rate of reaction at 80 s. Show all your working. rate = units The rate equation for this reaction is shown. rate = k [(CH3)3CCl ] Calculate the value of the rate constant, k, for this reaction and give its units. k = units
8. Reaction kinetics  →  8.1. Rate of reaction
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X is a metallic element. Draw a fully labelled diagram to show how the standard electrode potential, E o, of X2+/ Xcould be measured. What are the conditions needed for the value measured to be a standard electrode potential? State the charge carriers that transfer current through the solutions, the wire. An electrochemical cell was set up consisting of an X2+/ Xhalf-cell (E o=–0.40 and an Ag+/ Aghalf-cell (E o = +0.80 . Write an equation for the reaction that would take place if the electrodes of this cell were connected by a wire. When the current was allowed to pass for a period of time, • the Ag electrode gained 1.30 g in mass, • the electrode made of metal X lost 0.67 g in mass. Calculate the Ar of metal X; hence suggest an identity for X. Show all your working. Use of the Data Booklet is relevant to this question. Ar = X is
1. Atomic structure  →  1.1. Particles in the atom and atomic radius
9. The Periodic Table: chemical periodicity  →  9.2. Periodicity of chemical properties of the elements in Period 3
1. Atomic structure  →  1.4. Ionisation energy
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Boron forms many useful compounds. The compound diborane, B2H6, can be used as a rocket fuel. It can be prepared by the reaction of boron trifluoride, BF3, with sodium borohydride, NaBH4. Balance this equation. BF3 + NaBH4 → B2H6 + NaBF4 Primary and secondary alcohols can be formed by the reaction of carbonyl compounds with NaBH4, which is a source of hydride ions, H–. Complete the mechanism for the reaction of butanone with hydride ions, H–, and draw the intermediate in the box. Include all necessary curly arrows and relevant dipoles. CH2CH3 CH2CH3 O C intermediate OH C step 1 H+ H– H3C H3C H Borane, BH3, is used to synthesise alcohols from alkenes. The reaction occurs in two steps. The BH2 group from BH3 bonds to the least substituted carbon atom of the double bond, and the remaining H from BH3 bonds to the other carbon. CH3 H CH3 CH3 C C CH3 CH3 H BH2 C C + BH3 H step 1 [O] CH3 CH3 CH3 H OH C C H CH3 Suggest the type of reaction in step 1. The diol Y can be prepared by the same method. CH3 CH3 H3C CH3 OH OH Y Draw the structure of the diene which could be used to prepare diol Y. Benzene, C6H6, and borazine, B3N3H6, have planar, cyclic structures. Describe the structure of and bonding in benzene, C6H6. In borazine, B3N3H6, the boron and nitrogen atoms alternate around the ring. Each ring atom has a single hydrogen atom bonded to it. All boron-nitrogen bonds in borazine are 0.144 nm in length, whereas in simple compounds B–N and B=N bond lengths are 0.154 nm and 0.136 nm respectively. Suggest and draw the structure of borazine.
16. Hydroxy compounds  →  16.1. Alcohols
14. Hydrocarbons  →  14.2. Alkenes
17. Carbonyl compounds  →  17.1. Aldehydes and ketones
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Sunset Yellow is a yellow colouring agent used in food and drinks, which can be made by the following route. In step 3 of this synthesis, a phenol-like compound, S, reacts with intermediate T made from amine R. Assume that the –SO3 – Na+ group does not react. SO3 – Na+ SO3 – Na+ O2N step 1 step 2 + Sunset Yellow step 3 NaOHR (C6H6NSO3Na) T S Q OH Na+ –O3S N N Suggest structures for compounds R, S and T and draw them in the boxes above. Suggest reagents and conditions for step 1, step 2. What type of organic salt is formed in step 2? Compound W has the following structure. NH2 H2N O How many σ and π bonds are present in a molecule of W? σ bonds π bonds The products of the reactions of W with cold HCl and with CH3CH2Br are soluble in water but not in organic solvents. Complete the table for these reactions of W. reagent structure of product (molecular formula given) type of reaction HCl (C4H9N2OCl ) CH3CH2Br (C6H13N2BrO)
21. Organic synthesis  →  21.1. Organic synthesis
11. Group 17  →  11.4. The reactions of chlorine
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The sequence of bases in DNA is a code for the order of amino acids in the primary structure of proteins. The diagram represents the stages involved in the formation of a protein from DNA. DNA ribosome protein A B2 B1 stage 1 etc. stage 3 stage 2 Identify the biochemical structures, A and B1, B2 etc. biochemical structure identity A B1, B2 etc. Name the biochemical processes involved in stages 1 and 3. process name of biochemical process stage 1 stage 3 Adenine is an integral part of DNA. N N N NH2 N H adenine State the molecular formula of adenine. Identify the three other nitrogenous bases in DNA. DNA has a double helical structure that consists of two strands linked together. What type of bonding exists between the phosphate and sugar groups within a DNA strand, different bases on the two strands? The breakdown of adenosine triphosphate, ATP, provides the energy for many cellular reactions. ATP + H2O → ADP + Pi What type of chemical reaction is this? X-ray crystallography can be useful in obtaining information about the structures of large organic molecules, such as ATP. The technique involves X-rays interacting with the electrons within the molecule. Which element in the molecule of ATP will interact most strongly with the X-ray beam? Explain why X-ray crystallography will not detect hydrogen atoms.
4. States of matter  →  4.2. Bonding and structure
21. Organic synthesis  →  21.1. Organic synthesis
14. Hydrocarbons  →  14.2. Alkenes
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Some metals are essential to biochemical processes. Complete the following table naming one metal in each case. biochemical process metal haemoglobin in oxygen transport transmission of nerve impulses enzyme cofactor Enzymes are a special type of protein molecule that catalyse biochemical reactions. Explain briefly the mechanism by which an enzyme breaks down a substrate molecule. Disulfide bonds play an important role in the stability of some proteins such as the keratin in human hair. The amino acid involved in the formation of a disulfide bond is cysteine, H2NCH(CH2SH)CO2H. At which level of protein structure (primary, secondary, tertiary) are disulfide bonds formed? Use a functional group in cysteine to show how disulfide bonds are formed. What type of chemical reaction is this? The NMR spectrum of cysteine, H2NCH(CH2SH)CO2H, shows five absorptions. After shaking a solution of cysteine with a few drops of D2O, the NMR spectrum shows only two absorptions, E and F, shown below. E F Identify the two types of protons responsible for the absorptions E and F. E F State and explain the splitting patterns of the absorptions E and F. E F
3. Chemical bonding  →  3.4. Covalent bonding and coordinate (dative covalent) bonding
12. Nitrogen and sulfur  →  12.1. Nitrogen and sulfur
14. Hydrocarbons  →  14.2. Alkenes
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Aspartame is an artificial sweetener that has the structure shown below. aspartame OH O O O NH2 H3C N H O Draw a circle around each chiral centre in aspartame. In the stomach, aspartame is hydrolysed by acid to form three organic products. On the diagram above, use arrows to indicate the two bonds that would be hydrolysed in the stomach. Draw the structures of the three products formed after complete acid hydrolysis of aspartame. Aspartame is soluble in water. By referring to the structure of aspartame, explain why it is soluble in water. Recently, nanotechnology has been involved in the development of a new natural sweetener, Nano Sugar, extracted from sugar cane. What is the approximate width of a nanoparticle?
4. States of matter  →  4.2. Bonding and structure
14. Hydrocarbons  →  14.2. Alkenes
13. An introduction to AS Level organic chemistry  →  13.4. Isomerism: structural isomerism and stereoisomerism
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