9701_s19_qp_22
A paper of Chemistry, 9701
Questions:
5
Year:
2019
Paper:
2
Variant:
2
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1
Methylpropane, (CH3)2CHCH3, is an isomer of butane, CH3(CH2)2CH3. Explain why methylpropane and butane are a pair of isomers. Identify the type of isomerism shown by methylpropane and butane. When a sample of butane is heated to 373 K, in the presence of a catalyst, and allowed to reach equilibrium the following reaction occurs. CH3(CH2)2CH3(CH3)2CHCH3∆H = –8.0 kJ mol–1 State and explain the effect on the composition of this equilibrium mixture when the temperature is increased to 473 K. 1mole of butane gas was added to a 1 dm3 closed system, at a constant temperature and pressure. The amount of butane and methylpropane was measured at regular time intervals. 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 time amount / mol Label the graph with a t to show the time taken to reach dynamic equilibrium. Use the graph to find the concentration of butane and methylpropane in the mixture at equilibrium. concentration of butane = mol dm–3 concentration of methylpropane = mol dm–3  Write an expression for Kc for this reaction.  Calculate a value for Kc and state its units.  Kc = units = 
7. Equilibria  →  7.1. Chemical equilibria: reversible reactions, dynamic equilibrium
14. Hydrocarbons  →  14.2. Alkenes
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2
Group17 elements are commonly referred to as the halogens. State and explain the trend in volatility of chlorine, bromine and iodine down the group. Hydrogen gas reacts with the different halogens under different conditions. State the conditions required for chlorine to react with hydrogen at room temperature. On heating, iodine reacts with hydrogen in a reversible reaction. Give the equation for this reaction. Include state symbols. Hydrogen chloride reacts with water. HCl + H2O H3O+ + Cl – In this reaction, one of the reactants behaves as a Brønsted-Lowry acid. What is meant by the term Brønsted-Lowry acid? Identify the reactant behaving as an acid and its conjugate base. acid conjugate base  Name the type of bond formed between H+ and H2O to make H3O+. For H3O+, predict its shape and the H–O–H bond angle. shape bond angle  
7. Equilibria  →  7.2. Brønsted–Lowry theory of acids and bases
11. Group 17  →  11.2. The chemical properties of the halogen elements and the hydrogen halides
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Period3 elements react with chlorine gas, Cl 2, to form chlorides. The table shows the differences in observations which occur when two Period3 chlorides are added to water. Period 3 chloride observations when added to water pH of solution formed with water NaCl White solid disappears. Colourless solution made. SiCl 4 Pale yellow solution forms. Bubbles form and the test-tube feels hot. White precipitate forms. 1–2 Write an equation for the reaction occurring when SiCl 4 is added to cold water. Include state symbols. Name the type of reaction occurring when SiCl 4 is added to water. Ignore the exothermic/endothermic nature of the reaction. Explain, in terms of bonding, why NaCl and SiCl 4 behave differently when added to water. Explain, in terms of electronegativity, why the bonding in NaCl is different from the bonding in SiCl 4. Cl 2dissolves in cold water and reacts with it. Cl 2 + H2O HCl + HCl O Identify the oxidation number of chlorine in each of the chlorine‑containing species in this reaction. chlorine-containing species Cl 2 HCl HCl O oxidation number of chlorine  Name the type of reaction occurring. Explain why chlorine is used in the purification of water. A mixture of HCl and HCl O is added to cold dilute NaOH. One of the products behaves as a bleach. Suggest the equation for the reaction occurring. 
11. Group 17  →  11.4. The reactions of chlorine
9. The Periodic Table: chemical periodicity  →  9.2. Periodicity of chemical properties of the elements in Period 3
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4
There are many different types of aliphatic and aromatic hydrocarbons. Name a naturally occurring source of aliphatic and aromatic hydrocarbons and outline how different hydrocarbons are separated from this source. name of source outline of separation of hydrocarbons  When alkanes are heated to high temperatures, in the absence of air, the molecules can break into smaller molecules. Identify the type of reaction occurring. Write an equation which describes the reaction occurring when heptane, C7H16, is heated in the absence of air, to form hexane, butane and ethene only. The equation for the complete combustion of ethene is shown. C2H4 + 3O2 2CO2 + 2H2O Calculate the volume, in dm3, of carbon dioxide formed in the complete combustion of 1.00 g of ethene at room temperature and pressure.  volume of CO2 = dm3 The table compares the reactivity of alkanes and alkenes with chlorine. alkanes alkenes name of the type of reaction with chlorine substitution addition and substitution name of the type of reacting species free radical electrophile and free radical During the first stage in the substitution reaction chlorine forms chlorine free radicals. Explain what is meant by the term free radical. Name and explain the type of bond breaking which occurs to form chlorine free radicals. Name the stage of the reaction mechanism which occurs when a methane molecule reacts with a chlorine free radical. Complete the equation for the reaction which occurs when a methane molecule reacts with a chlorine free radical. C H H H + + •Cl H  Carbon atoms can form σ and π bonds within hydrocarbon molecules. Explain the following statement with reference to σ and π bonds. Alkenes react with electrophiles but alkanes do not. 
14. Hydrocarbons  →  14.1. Alkanes
14. Hydrocarbons  →  14.2. Alkenes
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5
Many naturally occurring esters are used as flavourings in food. The structure of ester V is shown. O O V Name V. V reacts with a reagent to form a salt of a carboxylic acid and an alcohol. Identify a reagent that could be used in this reaction. Draw the displayed formula of the alcohol made during this reaction.  State one other possible use for V, apart from as a food flavouring. Ester W is made up of 54.5% carbon, 9.1% hydrogen and 36.4% oxygen. Calculate the empirical formula of W.  State what additional information is required to determine the molecular formula of W. Compounds X, Y and Z are shown. They all have the same molecular formula. O O X OH O O O Y Z Deduce the molecular formula of X, Y and Z. In three experiments, sodium is added to separate samples of X, Y and Z. Complete the table to show the observations for each of these three experiments. Ignore any temperature changes which may occur. experiment observations Na + X Na + Y Na + Z  Sodium carbonate solution reacts with methanoic acid. Write the equation for this reaction. 
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
18. Carboxylic acids and derivatives  →  18.2. Esters
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