Chemistry 9701/22 October/November 2020: question paper and mark scheme

Question

Atoms contain the subatomic particles electrons, protons and neutrons. Protons and electrons were discovered by observations of their behaviours in electric fields. (a) The diagram shows the behaviour of separate beams of electrons and protons in an electric field. protons charge on plate electrons charge on plate source (i) Complete the diagram with the relative charge of each of the electrically charged plates. [1] (ii) On the diagram, draw a line to show how a separate beam of neutrons from the same source behaves in the same electric field. [1] (b) Electrons in atoms up to 36Kr are distributed in s, p and d orbitals. (i) State the number of occupied orbitals in an isolated atom of 36Kr. type of orbital s p d number of orbitals [3] (ii) Complete the diagram to show the number and relative energies of the electrons in an isolated atom of 14Si. 4s 3p 3s 2p 2s 1s [2] (iii) The diagram shows a type of orbital. State the total number of electrons that exist in all orbitals of this type in an atom of 9F. . …… [1] (iv) The first ionisation energies of elements in the first row of the d block (21Sc to 29Cu) are very similar. For all these elements, it is a 4s electron that is lost during the first ionisation. Suggest why the first ionisation energies of these elements are very similar. . …… . …… . …… . …… [3] (c) Hydron is a general term used to represent the ions 11H+, 12H+ and 13H+. State, in terms of subatomic particles in the nucleus, what is the same about each of these ions and what is different. same . …… different . …… [1] [Total: 12]

Question

The Period 3 elements, Na to S, all react with oxygen to form oxides. (a) State the trend in acid/base behaviour of the oxides of the Period 3 elements, from Na to S. . …… . …… [1] (b) State and explain the trend, from Na to S, in the maximum oxidation number of the Period 3 elements in their oxides. . …… . …… . …… [2] (c) Sodium oxide and phosphorus(V) oxide both react with water. Name the product of each reaction. reaction product sodium oxide with water phosphorus(V) oxide with water [2] (d) Explain why phosphorus(V) oxide has a low melting point of approximately 300 °C but magnesium oxide has a high melting point of approximately 2850 °C. . …… . …… . …… . …… . …… . …… [3] (e) Aluminium oxide, Al 2O3, reacts separately with both acids and alkalis. (i) Write an equation for the reaction of aluminium oxide with excess aqueous hydrochloric acid. . …… [1] (ii) Write an equation for the reaction of aluminium oxide with excess aqueous sodium hydroxide. . …… [1] (f) Describe the lattice structure of silicon(IV) oxide. Your answer should include reference to the arrangement of the silicon and oxygen atoms and the bonds between them. . …… . …… . …… . …… [2] (g) Sodium oxide and silicon(IV) oxide react to form sodium silicate(IV), Na2SiO3. Sodium oxide is obtained from the thermal decomposition of sodium carbonate. Write equations for the following reactions: (i) sodium oxide with silicon(IV) oxide . …… [1] (ii) the thermal decomposition of sodium carbonate, forming sodium oxide and carbon dioxide. . …… [1] [Total: 14]

Question

PCl 5, PCl 3 and NCl 3 are halides of Group 15 elements. (a) PCl 5 can be formed from the reaction of phosphorus with chlorine. PCl 5 has a melting point of 161 °C. (i) Write an equation for the formation of PCl 5 from the reaction of phosphorus and chlorine. . …… [1] (ii) State the type of structure and bonding shown by liquid PCl 5. . …… [1] (b) A small amount of PCl 5 is added to excess water. The PCl 5 reacts vigorously to form a colourless solution. (i) Give one other observation you would make when PCl 5 reacts with excess water. . …… [1] (ii) Write the equation for the reaction of PCl 5 with excess water. . …… [1] (iii) Estimate the pH of the resulting solution. . …… [1] (c) PCl 3 is used to convert alcohols to chloroalkanes, such as compound T. T Cl Cl A possible synthesis of T is shown. reaction 1 using PCl 3 O OH Cl HO HO Cl OH (i) Identify a reagent that could be used in reaction 1. . …… [1] (ii) T exhibits optical isomerism. Explain what is meant by the term optical isomer and circle any atom(s) in T that give rise to optical isomerism. T Cl Cl . …… . …… . …… [2] (iii) T is a minor product in the reaction of compound S with excess HCl. S Draw the structure of the major product of the reaction of S with excess HCl. [1] (d) NCl 3 is a yellow liquid that can be used to bleach flour. (i) Predict the shape of the NCl 3 molecule and the Cl –N–Cl bond angle. shape . …… bond angle . …… [2] (ii) NCl 3 reacts with water to form HOCl, a weak Brønsted-Lowry acid. Explain fully what is meant by the term weak Brønsted-Lowry acid. . …… . …… . …… [2] (iii) NCl 3(l) decomposes according to the equation shown. 2NCl 3(l) → N2(g) + 3Cl 2(g) A sealed container of volume 250 cm3 contains an unreactive gas at a pressure of 1.00 × 105 Pa. 0.241 g of NCl 3(l) was injected into the sealed container. The sealed container was heated to make the NCl 3(l) decompose fully and then cooled to 20 °C. Calculate the final total pressure inside the sealed container at 20 °C after the NCl 3(l) has fully decomposed. final total pressure = …… Pa [4] [Total: 17]

Question

Some reactions of compound G are shown. G O O reaction 3 OH Tollens’ reagent OH H HO reaction 1 H2SO4, heat reaction 2 Na reaction 4 under reflux HOOC(CH2)2COOH H O O (a) (i) State the type of reaction that occurs in reaction 1. . …… [1] (ii) Suggest the reagent(s) and conditions required for reaction 1. . …… . …… [2] (iii) Draw the structure of the organic product, H, from reaction 2. [1] (iv) State what you would observe in reaction 3. . …… [1] (v) Give the type of reaction shown by reaction 4. . …… [1] (b) G and J are structural isomers of each other. G J O O OH OH H H (i) Name the type of structural isomerism shown by G and J. . …… [1] (ii) Suggest one chemical test that can distinguish G from J. Give the result of the test with each compound. test . …… result with G . …… result with J …… [2] In the reaction schemes below, G and J are converted into organic compound K. G J NaBH4 NaBH4 Al 2O3 Al 2O3 HO(CH2)3CH2OH K HO(CH2)2CH(OH)CH3 heat heat (iii) State the role of NaBH4 in the reactions with G and J. . …… [1] (iv) Identify the organic product K. . …… [1] (c) P and Q have the same molecular formula as G. P Q O O HO OH Complete the table with the expected observations for the reactions of P and Q with the named reagents. reagent result with P result with Q Br2(aq) 2,4-dinitrophenylhydrazine aqueous sodium carbonate [3] (d) The structure of compound L is shown. R represents a hydrocarbon chain. L O R O A student was asked to deduce the full structure of L. The student analysed L using infrared spectroscopy. The following spectrum was obtained. 100 transmittance % 50 X Y Z 0 4000 3000 2000 1500 1000 500 wavenumber / cm –1 (i) Identify the bonds responsible for the absorptions marked X and Z. X …… Z …… [1] Absorption Y shows that L has a C=C bond present in the R group. The student decided to treat L with hot concentrated acidified potassium manganate(VII). The products of the reaction are shown. O L hot concentrated O OH O acidified KMnO4 + O R O M CH3(CH2)4COOH (ii) Name M. . …… [1] (iii) Use the information in (d) to deduce the molecular formula of L. molecular formula of L = …… [1] [Total: 17]