9701_s08_qp_2 - revisedeck

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Examiner s Use The structural formulae of water, methanol and methoxymethane, CH3OCH3, are given below. O H H O H3C H O H3C CH3 How many lone pairs of electrons are there around the oxygen atom in methoxymethane? Suggest the size of the C–O–C bond angle in methoxymethane. The physical properties of a covalent compound, such as its melting point, boiling point, vapour pressure, or solubility, are related to the strength of attractive forces between the molecules of that compound. These relatively weak attractive forces are called intermolecular forces. They differ in their strength and include the following. A interactions involving permanent dipoles B interactions involving temporary or induced dipoles C hydrogen bonds By using the letters A, B, or C, state the strongest intermolecular force present in each of the following compounds. For each compound, write the answer on the dotted line. ethanal CH3CHO ethanol CH3CH2OH methoxymethane CH3OCH3 2-methylpropane (CH3)2CHCH3 For Examiner’s Use Methanol and water are completely soluble in each other. Which intermolecular force exists between methanol molecules and water molecules that makes these two liquids soluble in each other? Draw a diagram that clearly shows this intermolecular force. Your diagram should show any lone pairs or dipoles present on either molecule that you consider to be important. When equal volumes of ethoxyethane, C2H5OC2H5, and water are mixed, shaken, and then allowed to stand, two layers are formed. Suggest why ethoxyethane does not fully dissolve in water. Explain your answer.

3. Chemical bonding → 3.6. Intermolecular forces, electronegativity and bond properties

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For Examiner’s Use The Periodic Table we currently use is derived directly from that proposed by Mendeleev in 1869 after he had noticed patterns in the chemical properties of the elements he had studied. The diagram below shows the first ionisation energies of the first 18 elements of the Periodic Table as we know it today. He H Ne Li Na Ar proton number first ionisation energy /kJ mol-1 15 16 Give the equation, including state symbols, for the first ionisation energy of fluorine. Explain why there is a general increase in first ionisation energies from sodium to argon. Explain why the first ionisation energy of aluminium is less than that of magnesium. For Examiner’s Use Explain why the first ionisation energy of sulphur is less than that of phosphorus. The table below refers to the elements sodium to sulphur and is incomplete. element Na Mg Al Si P S melting point high conductivity high Complete the ‘melting point’ row by using only the words ‘high’ or ‘low’. Complete the ‘conductivity’ row by using only the words ‘high’, ‘moderate’ or ‘low’. When Mendeleev published his Periodic Table, the elements helium, neon and argon were not included. Suggest a reason for this.

1. Atomic structure → 1.4. Ionisation energy

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For Examiner’s Use When hydrocarbons such as petrol or paraffin wax are burned in an excess of air in a laboratory, carbon dioxide and water are the only products. When petrol is burned in a car engine, nitrogen monoxide, NO, is also formed. Explain how NO is formed in an internal combustion engine but not formed when a small sample of petrol is burnt in an evaporating basin. The engines of modern motor cars have exhaust systems which are fitted with catalytic converters in order to reduce atmospheric pollution from substances such as NO. State three more pollutants, other than CO2 and H2O, that are present in the exhaust gases of a car engine. and and What is the active material present in the catalytic converter? Write one balanced equation to show how NO is removed from the exhaust gases of a car engine by a catalytic converter. NO is also formed when nitrosyl chloride, NOCl, dissociates according to the following equation. 2NOCl 2NO+ Cl2Different amounts of the three gases were placed in a closed container and allowed to come to equilibrium at 230 °C. The experiment was repeated at 465 °C. The equilibrium concentrations of the three gases at each temperature are given in the table below. concentration / mol dm–3 temperature / °C NOCl NO Cl 2 2.33 × 10–3 1.46 × 10–3 1.15 × 10–2 3.68 × 10–4 7.63 × 10–3 2.14 × 10–4 For Examiner’s Use Write the expression for the equilibrium constant, Kc , for this reaction. Give the units. Calculate the value of Kc at each of the temperatures given. 230 °C 465 °C Is the forward reaction endothermic or exothermic? Explain your answer. The temperature of the equilibrium was then altered so that the equilibrium concentrations of NOCl and NO were the same as each other. What will be the effect on the equilibrium concentration of NOCl when the following changes are carried out on this new equilibrium? In each case, explain your answer. The pressure of the system is halved at constant temperature. A mixture of NOCland NOcontaining equal numbers of moles of each gas is introduced into the container at constant temperature.

12. Nitrogen and sulfur → 12.1. Nitrogen and sulfur

2. Atoms, molecules and stoichiometry → 2.4. Reacting masses and volumes (of solutions and gases)

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For Examiner’s Use Two types of isomerism found in organic compounds are structural isomerism and cis-trans isomerism. Draw displayed formulae for two structural isomers of C2H4Br2, D E the cis- and the trans- isomers of C2H2Br2. cis trans The cis- isomer of C2H2Br2 can be converted into one of the structural isomers of C2H4Br2. State the reagentand conditions you would use to do this. Which of your structural isomers, D or E, would be formed? Explain your answer. isomer formed is reason

13. An introduction to AS Level organic chemistry → 13.4. Isomerism: structural isomerism and stereoisomerism

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For Examiner’s Use Ethanedial is used in the production of fabrics which have permanent creases. O O C H ethanedial C H Ethanedial undergoes many of the reactions of aldehydes. Ethanedial reacts with Tollens’ reagent. What would you see if you carried out this reaction? What is the structural formula of the organic compound formed? Ethanedial reacts with hydrogen cyanide, HCN, to give compound F. What is the structural formula of F? What type of reaction is this? What is the structural formula of the compound formed when F is heated with an aqueous mineral acid such as dilute sulphuric acid? For Examiner’s Use Ethanedial can be oxidised and reduced. What is the structural formula of the organic compound formed when ethanedial is heated under reflux with an excess of acidified potassium dichromate(? What is the structural formula of the compound formed when ethanedial is reduced? What reagent would be used for this reduction? When ethanedial is reacted with NaOH and the product treated with a mineral acid such as dilute sulphuric acid, the following reaction sequence takes place. I CHOCHO + NaOH → HOCH2CO2Na II HOCH2CO2Na + H+ → HOCH2CO2H + Na+ What type of reaction is the overall change? An isomer of ethanedial exists which reacts with sodium metal to give hydrogen. Suggest the displayed formula of this isomer.

13. An introduction to AS Level organic chemistry → 13.1. Formulas, functional groups and the naming of organic compounds

17. Carbonyl compounds → 17.1. Aldehydes and ketones

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