9701_s13_qp_23 - revisedeck

9701_s13_qp_23

A paper of Chemistry, 9701

Questions:

5

Year:

2013

Paper:

2

Variant:

3

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1

Carbon disulﬁ de, CS2, is a volatile, ﬂ ammable liquid which is produced in small quantities in volcanoes. The sequence of atoms in the CS2 molecule is sulfur to carbon to sulfur. Draw a ‘dot-and-cross’ diagram of the carbon disulﬁ de molecule. Show outer electrons only. Suggest the shape of the molecule and state the bond angle. shape bond angle Carbon disulﬁ de is readily combusted to give CO2 and SO2. Construct a balanced equation for the complete combustion of CS2. Deﬁ ne the term standard enthalpy change of combustion, . For Examiner’s Use Calculate the standard enthalpy change of formation of CS2 from the following data. Include a sign in your answer. standard enthalpy change of combustion of CS2 = –1110 kJ mol–1 standard enthalpy change of formation of CO2 = –395 kJ mol–1 standard enthalpy change of formation of SO2 = –298 kJ mol–1 Carbon disulﬁ de reacts with nitrogen monoxide, NO, in a 1:2 molar ratio. A yellow solid and two colourless gases are produced. Construct a balanced equation for the reaction. What is the change in the oxidation number of sulfur in this reaction? from to

5. Chemical energetics → 5.1. Enthalpy change, \(\Delta H\)

12. Nitrogen and sulfur → 12.1. Nitrogen and sulfur

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2

For Examiner’s Use Methanol, CH3OH, can be produced industrially by reacting carbon monoxide, CO, with hydrogen, H2. CO+ 2H2CH3OH∆H = –91 kJ mol–1 The process is carried out at 4 × 103 kPa (40 atmospheres) and 1150 K. State Le Chatelier's Principle. From your understanding of Le Chatelier’s Principle, state the conditions of temperature and pressure that could be used in order to produce an increased yield of methanol in this process. In each case, explain why the yield would increase. temperature explanation pressure explanation For Examiner’s Use The carbon monoxide for use in the production of methanol may be formed by reacting carbon dioxide with hydrogen. CO2+ H2CO+ H2OKc = 1.44 at 1200 K A mixture containing 0.70 mol of CO2, 0.70 mol of H2, 0.30 mol of CO and 0.30 mol of H2O was placed in a 1 dm3 ﬂ ask and allowed to come to equilibrium at 1200 K. Calculate the amount, in moles, of each substance present in the equilibrium mixture at 1200 K. CO2 + H2 CO + H2O initial 0.70 0.70 0.30 0.30 moles

7. Equilibria → 7.1. Chemical equilibria: reversible reactions, dynamic equilibrium

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3

For Examiner’s Use This question refers to the elements in the section of the Periodic Table shown below. H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca transition elements Ga Ge As Se Br Kr From this list of elements, identify in each case one element that has the property described. Give the symbol of the element. An element that has molecules which consist of single atoms. An element that has a molecule which contains exactly four atoms. The element that is a liquid at room temperature and pressure. The element in Period 3 (Na to Ar) that has the largest atomic radius. The element in Period 3 (Na to Ar) that has the highest melting point. The element in Period 3 (Na to Ar) that forms the largest anion. An element that reacts with water to give a solution that can behave as an oxidising agent. For Examiner’s Use The formulae and melting points of some of the oxides of the elements in Period 3, Na to Cl, are given in the table. formula of oxide Na2O MgO Al 2O3 SiO2 P4O6 SO2 Cl 2O7 m.p. / °C –73 –92 Give the formulae of two of these oxides that have simple molecular structures. and Give the formula of one of these oxides that will give no reaction with water when placed in it for a long time. Give the formula of the product formed when MgO is reacted with SO2. The melting points of the elements Si to Cl are given in the table. element Si P S Cl m.p. / °C –102 Explain why the melting point of Si is very much greater than those of the other three elements. Suggest why the melting points of the other three elements are in the order S > P > Cl.

9. The Periodic Table: chemical periodicity → 9.2. Periodicity of chemical properties of the elements in Period 3

9. The Periodic Table: chemical periodicity → 9.1. Periodicity of physical properties of the elements in Period 3

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4

For Examiner’s Use Compound Q, heptan-2-one, is found in some blue cheeses. CH3(CH2)4COCH3 compound Q Compound Q may be reduced to R. Compound R may be dehydrated to give two different products, S and T. In the boxes below, draw the structural formulae of R, S, and T. CH3(CH2)4COCH3 R reduce S T dehydrate State the reagents that would be used for each of these reactions in a school or college laboratory. reduction dehydration For Examiner’s Use In the boxes below, write the structural formula of the organic compound formed when Q is reacted separately with each reagent under suitable conditions. If you think no reaction occurs, write 'NO REACTION' in the box. Tollens’ reagent HCN K2Cr2O7 / H+ The ﬁ rst stage of cheese making is to produce 2-hydroxypropanoic acid (lactic acid) from milk. CH3CH(OH)CO2H lactic acid Other than the use of a pH indicator, what reagent could you use to conﬁ rm the presence of some lactic acid in a sample of heptan-2-one? State what observation you would make. reagent observation

17. Carbonyl compounds → 17.1. Aldehydes and ketones

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

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5

For Examiner’s Use Compounds containing the allyl group, CH2=CHCH2–, have pungent smells and are found in onions and garlic. Allyl alcohol, CH2=CHCH2OH, is a colourless liquid which is soluble in water. Allyl alcohol behaves as a primary alcohol and as an alkene. Give the structural formula of the organic compound formed when allyl alcohol is reacted separately with each of the following reagents. acidiﬁ ed potassium dichromate(, heating under reﬂ ux bromine in an inert organic solvent cold, dilute, acidiﬁ ed potassium manganate(hot, concentrated, acidiﬁ ed potassium manganate( Allyl alcohol undergoes the following reactions. When reacted with concentrated HCl at 100 °C, CH2=CHCH2Cl is formed. State as fully as you can what type of reaction this is. When reacted with MnO2 at room temperature, CH2=CHCHO is formed. What type of reaction is this? For Examiner’s Use Allyl alcohol can be converted into propanal in two steps. step I step II CH2=CHCH2OH CH3CH2CH2OH CH3CH2CHO What reagents and conditions would be used for each step? step I reagentconditionstep II reagentconditionAllyl alcohol and propanal are isomers. What form of isomerism do they display? Allyl alcohol may also be converted into propanal by using a ruthenium(catalyst in water. ruthenium(catalyst CH2=CHCH2OH CH3CH2CHO Suggest what is unusual about this single step reaction.

16. Hydroxy compounds → 16.1. Alcohols

14. Hydrocarbons → 14.2. Alkenes

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