Alkenes — Paper 4 · IGCSE Sciences - Co-ordinated (Double) 0654

6 (a) Alkanes and alkenes are two homologous series (families) of hydrocarbons. Alkanes are obtained from petroleum. Alkenes are produced from alkanes. (i) Name the processes used to separate petroleum into alkanes, … produce alkenes from alkanes. … [2] (ii) State two conditions needed inside the reaction vessel when alkenes are produced from alkanes. 1 … 2 … [2] (iii) Fig. 6.1 shows the structure of one molecule of ethene. H H C C H H Fig. 6.1 Ethene reacts to form poly(ethene), a solid made of polymer molecules. Complete the structure of part of a molecule of poly(ethene). Your diagram should contain four carbon atoms. C [3] (b) Polymers are used to make paint. Steel parts of car bodies are painted to prevent rusting. Fig. 6.2 shows a small area of rust on a car. area of rust Fig. 6.2 (i) Suggest how the small area of rust formed on the car in Fig. 6.2. Explain your answer in terms of a chemical reaction. … … … [2] (ii) State the advantage of galvanising rather than painting as a method of preventing rusting. … … [1]

10 marks

Mark scheme: 6(a)(i) fractional distillation ; (catalytic / thermal) cracking ; 2 6(a)(ii) high temperature ; high pressure ; catalyst ; max 2 6(a)(iii) linear chain of 4 carbons ; 2 H on each C ; all single bonds ; 3 6(b)(i) any reasonable cause of paint removal ; causing steel to, be exposed to / react with, oxygen / owtte ; causing steel to, be exposed to / react with, water / owtte ; max 2 6(b)(ii) protection continues when (zinc) layer damaged / reference to sacrificial protection ; 1

This question in 0654/42 May/June 2017

11 Petroleum is a liquid fossil fuel that is a mixture containing many different hydrocarbons. Petroleum is extracted from the Earth and is then processed into useful products. (a) Suggest why petroleum is described as a fossil fuel, but wood is not a fossil fuel. … … [1] (b) Fractional distillation is used to separate petroleum into simpler, more useful mixtures called fractions. Fig. 11.1 shows this process and two of the useful fractions obtained. gasoline fractional distillation column gas oil hot petroleum Fig. 11.1 (i) State the two physical changes involved in forming each fraction. … followed by … [1] (ii) The gasoline fraction has a lower average boiling point than gas oil. Explain this in terms of molecular sizes and intermolecular forces. … … … … [3] (c) Cracking breaks down large, saturated hydrocarbon molecules into smaller ones. This process also produces some unsaturated hydrocarbons. The equation shows a chemical reaction that occurs during cracking. C16H34 CxHy + 3C2H4 + C3H6 Determine the values of x and y. x = … y = … [1] (d) (i) Compound W has the formula C3H6. State the name of compound W. … [1] (ii) Compound W is added to aqueous bromine and shaken. Describe the changes observed, if any. Explain your answer. change … explanation … … [2] (iii) Compound W reacts with hydrogen gas, H2, in an addition reaction to produce compound X. Deduce the formula of compound X and complete the diagram in Fig. 11.2 of a molecule of X. formula … H C H Fig. 11.2 [2]

11 marks

Mark scheme: 11(a) reference to long time required to form fossil fuels / AVP ; 1 11(b)(i) evaporation followed by condensation ; 1 11(b)(ii) (average) size / surface area of molecules in gasoline is lower ; intermolecular forces / forces between molecules are lower ; lower (thermal) energy / lower temperature required to separate molecules / overcome forces ; 3 11(c) x = 7 and y = 16 ; 1 11(d) propene ; 1 11(d)(ii) bromine decolourised / orange to colourless ; propene is an alkene / is unsaturated / double bond ; 2 11(d)(iii) C3H8 ; same number of C and H as in formula and correctly bonded ; 2

This question in 0654/41 Oct/Nov 2017

11 (a) Fig. 11.1 shows the structure of a molecule of an alkane. H H H H C C C H H H H Fig. 11.1 (i) Name this alkane. … [1] (ii) Complete Fig. 11.2 to show the structure of a molecule of the alkene that contains only three carbon atoms. C C C H Fig. 11.2 [2] (b) Fig. 11.3 shows clay pots being heated strongly in a kiln. The alkane, C3H8, is supplied to the gas burner. Hot gases circulate through the kiln, heating the clay pots and then leaving through the top of the kiln. gas mixture leaving the kiln kiln wall 950 ºC clay pot air alkane C3H8 gas burner Fig. 11.3 (i) Explain why the gas mixture leaving the kiln contains nitrogen and argon. … … … [2] (ii) State two gases that are produced by the combustion of C3H8. 1 … 2 … [1] (c) Sometimes clay pots are covered with a glaze before they go into the kiln. Glaze is a mixture of solid compounds that melt at high temperatures. It forms a coloured, shiny layer on the pots as they cool. Four compounds found in a glaze are listed. calcium carbonate, CaCO3 cobalt oxide, CoO copper oxide, CuO silicon dioxide, SiO2 (i) Predict which two compounds produce colours in the glaze layer. Explain your prediction. compounds … and … explanation … … [2] (ii) Explain, in terms of its structure, why silicon dioxide has a high melting point. … … … [2]

10 marks

Mark scheme: 11(a)(i) propane ; 1 11(a)(ii) 1 single bond and 1 double bond between the carbons ; all else correct ; 2 11(b)(i) nitrogen and argon from the air taken in with the fuel ; nitrogen and argon, are inert / do not react / do not burn / are unaffected ; 2 Question Answer Marks 11(b)(ii) two from carbon dioxide carbon monoxide water vapour ; 1 11(c)(i) cobalt oxide / CoO and copper oxide / CuO ; reference to transition metals ; 2 11(c)(ii) it has a, giant / lattice, structure or large number of bonds / it is a macromolecule ; large amount of thermal energy required to break the bonds ; 2

This question in 0654/42 Oct/Nov 2017

11 Alkanes and alkenes are homologous series of hydrocarbons. (a) (i) Complete Table 11.1 by stating the four missing hydrocarbon names. Table 11.1 number of carbon atoms in name of alkane name of alkene one molecule 2 … … 3 propane propene 4 … … [2] (ii) Explain why no alkene molecules contain only one carbon atom. … … [1] (b) Fig. 11.1 shows apparatus a teacher uses to demonstrate the redox reaction between methane, CH4, and the black solid, copper oxide, CuO. copper oxide reaction tube methane strong heat condensed water limewater Fig. 11.1 As methane flows over the hot copper oxide, the black solid turns to pink copper. (i) Describe the observation that shows the presence of carbon dioxide in the gases leaving the reaction tube. … [1] (ii) Construct the balanced symbolic equation for the reaction between methane and copper oxide. … [2] (iii) In the reaction, copper ions, Cu2+, are reduced. Define, in terms of electrons, the term reduced. … … [1] (iv) Methane is the main constituent of natural gas. Suggest why natural gas is described as a fossil fuel. … … [1]

8 marks

Mark scheme: 11(a)(i) ethane ethene butane butane 2 or 3 correct ; 4 correct ; 2 11(a)(ii) the idea that at least two carbon atoms required for double bond ; 1 11(b)(i) limewater goes milky ; 1 Question Answer Marks 11(b)(ii) 4CuO + CH4 → 4Cu + CO2 + 2H2O correct formulae ; correctly balanced ; 2 11(b)(iii) (copper ions) gain electrons ; 1 11(b)(iv) reference to time required for formation / AVP ; 1

This question in 0654/43 Oct/Nov 2017

11 Petroleum contains hydrocarbons. (a) Name one fraction obtained from petroleum and state its use. fraction … use … [1] (b) Most of the hydrocarbons in petroleum are alkanes. Complete Table 11.1 by stating the names of the alkanes next to their chemical formulae. Table 11.1 formula of alkane name of alkane CH4 C3H8 C4H10 [2] (c) Alkenes are produced by heating alkanes strongly in the presence of a catalyst. The equation shows a reaction in which two different alkenes are produced from an alkane. C15H32 2C2H4 + C3H6 + C8H18 (i) Name the process that produces alkenes from alkanes. … [1] (ii) Calculate the mass of ethene, C2H4, that is obtained from 42.4 g of the alkane C15H32 by completing steps 1, 2 and 3. Show your working. step 1 Show that 0.2 moles of the alkane C15H32 has a mass of 42.4 g. [Ar : C, 12; H, 1] … step 2 State the number of moles of ethene obtained from 0.2 moles of C15H32. number of moles = … step 3 Use your result in step 2 to calculate the mass of ethene obtained. (Mr ethene = 28) mass of ethene = … g [4] (d) Complete the dot-and-cross diagram to show the covalent bonding in an ethene molecule. H H C C H H [2]

10 marks

Mark scheme: 11(a) refinery gas / gasoline / diesel / gas oil for fuel ; 1 11(b) methane propane butane 2 correct ; 3 correct ; 2 11(c)(i) (catalytic / thermal) cracking ; 1 11(c)(ii) step 1 calculate Mr (12 × 15) + (1 × 32) OR 212 ; moles = 42.4 ÷ 212 (= 0.2) / 0.2 × 212 (= 42.4) ; step 2 0.2 × 2 OR 0.4 ; step 3 0.4 × 28 = 1.2 (g) ; 4 11(d) two shared pairs between carbons ; four shared pairs between carbon and hydrogens ; 2

This question in 0654/41 Oct/Nov 2018

11 Ethene, C2H4, has the smallest molecules in the homologous series of alkenes. (a) (i) State the name of the alkene that contains three carbon atoms in each of its molecules. … [1] (ii) Complete the structure in Fig. 11.1 to show an alkene molecule that contains four carbon atoms. H H C H Fig. 11.1 [2] (b) Ethene reacts with bromine to form the compound dibromoethane, C2H4Br2. The balanced equation for the reaction is shown. C2H4 + Br2 C2H4Br2 (i) State the type of chemical reaction that occurs between ethene and bromine. … [1] (ii) Deduce the colour, if any, of the compound dibromoethane. Explain your answer. colour … explanation … … [2] (c) Ethene reacts with steam to produce ethanol, C2H5OH. The balanced equation for the complete combustion of ethanol is shown. C2H5OH + 3O2 2CO2 + 3H2O Complete steps 1 to 4 to calculate the volume of oxygen gas that reacts with 1.15 g of ethanol. Show your working. step 1 Show that the relative formula mass of ethanol is 46. [Ar: C, 12; H, 1; O, 16] … step 2 Calculate the number of moles of ethanol in 1.15 g. number of moles of ethanol = … step 3 Using your answer to step 2 and the balanced equation, state the number of moles of oxygen that reacts with 1.15 g of ethanol. number of moles of oxygen = … step 4 Using your answer to step 3, calculate the volume, in dm3, of oxygen gas that reacts with 1.15 g of ethanol. [Molar gas volume = 24 dm3] volume of oxygen gas = … dm3 [4]

10 marks

Mark scheme: 11(a)(i) propene ; 1 11(a)(ii) C=C double bond ; all else correct ; 2 11(b)(i) addition ; 1 11(b)(ii) colourless ; bromine forms colourless compounds with unsaturated hydrocarbons / alkenes ; 2 11(c) step 1 (12 × 2) + (1 × 6) + 16 (= 46) ; step 2 1.15 ÷ 46 = 0.025 ; step 3 0.025 × 3 = 0.075 ; step 4 0.075 × 24 = 1.8 (dm3) ; 4

This question in 0654/43 Oct/Nov 2018

2 Ethene, C2H4, and propene, C3H6, are in the same homologous series. (a) (i) Define the term homologous series. … … … [2] (ii) Name the homologous series to which ethene and propene belong. … [1] (b) Atoms in a molecule of ethene are held together by covalent bonds. Fig. 2.1 shows the outer shell electrons in a carbon atom and a hydrogen atom. H C Fig. 2.1 In the space below, draw the dot-and-cross diagram to show all the outer shell electrons in a molecule of ethene. [3] (c) Ethane is produced by the addition reaction between ethene and hydrogen. (i) Write the symbol equation for the addition reaction between ethene and hydrogen. … [2] (ii) Predict the product formed when propene reacts with hydrogen. Explain your answer. product … explanation … … [2] [Total: 10]

10 marks

Mark scheme: 2(a)(i) same general formula ; similar chemical properties ; 2 2(a)(ii) alkenes ; 1 2(b) correct arrangement of atoms ; 2 carbon atoms sharing 2 bonding pairs ; 2 hydrogen atoms sharing bonding pair with each carbon atom ; 3 2(c)(i) C2H4 + H2 → C2H6 LHS ; RHS ; 2 2(c)(ii) to make propane ; same homologous series / similar or same reactions / ref. to double bond / it is also an addition reaction ; 2

This question in 0654/42 Oct/Nov 2019

11 A homologous series is a family of compounds which have the same general formula and similar chemical properties. Alkanes and alkenes are examples of homologous series. Ethane, C2H6, and propane, C3H8, are alkanes. Ethene, C2H4, and propene, C3H6, are alkenes. (a) (i) The general formula for alkanes is CnH2n+2. Suggest the general formula for alkenes. … [1] (ii) Complete Fig. 11.1 to show the structures of an ethane molecule and an ethene molecule. C C C C ethane ethene Fig. 11.1 [2] (b) (i) The equation for the complete combustion of propane is shown. C3H8 + 5O2 3CO2 + 4H2O Complete steps 1 to 3 to calculate the volume of carbon dioxide when 1000 dm3 of propane is burned. All gas volumes are measured at room temperature and pressure. The volume of 1 mole of any gas is 24 dm3 at room temperature and pressure. step 1 Calculate the number of moles in 1000 dm3 of propane. number of moles = … step 2 Use your answer to step 1 and the balanced equation to calculate the number of moles of carbon dioxide produced by burning 1000 dm3 of propane. number of moles = … step 3 Calculate the volume of carbon dioxide produced by burning 1000 dm3 of propane. volume = … dm3 [3] (ii) Describe the effect of increased emission of carbon dioxide on the environment. … … … [2] (c) Two reactions of the alkenes ethene and propene are: • combustion • polymerisation. Describe one other chemical reaction of alkenes. Explain why alkenes can undergo this chemical reaction. reaction … explanation … … [2] (d) (i) State one difference between addition polymerisation and condensation polymerisation. … … … [1] (ii) Nylon is a condensation polymer made from monomer molecules A and B. Fig. 11.2 shows a few of these monomer molecules. A B A B A O O H H O O H H O O C C N N C C N N C C Cl Cl H H Cl Cl H H Cl Cl Fig. 11.2 Fig. 11.3 shows an incomplete section of the nylon molecule. N C Fig. 11.3 Complete Fig. 11.3 to show how a molecule of monomer B has chemically combined with a molecule of monomer A. [1] (iii) State the formula of the other compound that is formed during the polymerisation to make nylon. … [1] [Total: 13]

13 marks

Mark scheme: 11(a)(i) CnH2n ; 1 11(a)(ii) ethane correctly drawn ; ethene correctly drawn ; 2 11(b)(i) 1000 / 24 = 41.7 ; 41.7 × 3 = 125.1 ; 125.1 × 24 = 3000 (dm3) ; 3 11(b)(ii) greenhouse, effect / gas / description of greenhouse effect ; climate change / global warming / other environmental effect ; AVP ; max 2 2 11(c) (named) addition reaction ; (both have) double bond / are unsaturated ; 2 11(d)(i) condensation polymerisation gives (small molecular) waste product / owtte ; 1 11(d)(ii) H O | || — ; 1 11(d)(iii) HCl ; 1

This question in 0654/43 Oct/Nov 2019

11 Propane and propene are both hydrocarbons. Fig. 11.1 shows the structure of a propene molecule. H H H C H C C H H Fig. 11.1 (a) Draw the structure of a propane molecule. [1] (b) Aqueous bromine is used to tell the difference between propane and propene. Describe the colour change, if any, that is seen when aqueous bromine is added to propane and to propene. propane … propene … [2] (c) Cracking is used to make propene. Describe cracking. Include what happens to the large hydrocarbon molecules during cracking, and the conditions needed for cracking. … … … … … … [4] (d) Fig. 11.2 shows the structure of a chloropropene molecule. Cl H C C H CH3 Fig. 11.2 Chloropropene is used to make the polymer poly(chloropropene). Draw the structure of poly(chloropropene). [1] [Total: 8]

8 marks

Mark scheme: 11(a) ; 1 11(b) bromine water remains orange (with propane) / bromine water is not decolourised (with propane) ; bromine water is decolourised (with propene) / bromine water changes from orange to colourless (with propene) ; 2 11(c) large hydrocarbon molecules are broken down / split up (into smaller molecules) ; to make, alkenes / named alkene other than propene ; plus any two from: high temperature / 300 to 600 °C ; catalyst / correctly named catalyst e.g. zeolite or porcelain ; high pressure / 50 to 200 atmospheres ; max 4 11(d) n ; 1

This question in 0654/42 Oct/Nov 2020

8 Fig. 8.1 shows the structures of ethene and of ethanol. H H H H C C H C C O H H H H H ethene ethanol Fig. 8.1 (a) Ethene is an unsaturated hydrocarbon. Explain the meanings of the underlined words. unsaturated … … hydrocarbon … … [2] (b) Ethene has a simple molecular structure. Ethene does not dissolve in water. State one other physical property of substances with a simple molecular structure. … [1] (c) Ethanol is an alcohol made by fermentation. (i) Ethanol is used in alcoholic drinks. State another use for ethanol. … [1] (ii) Describe how ethanol is made by fermentation. … … … … … [4] [Total: 8]

8 marks

Mark scheme: 8(a) (ethene is unsaturated because) it contains a double bond between the carbon atoms ; (ethene is a hydrocarbon because) it contains carbon and hydrogen (atoms) only / AW ; 2 8(b) poor electrical conductor / low boiling point / evaporates easily / volatile ; 1 8(c)(i) solvent / fuel ; 1 8(c)(ii) fermentation requires water ; fermentation requires sugar / named sugar ; fermentation requires yeast / enzyme / zymase ; fermentation requires suitable temperature ; reference to anaerobic respiration ; max 4 4

This question in 0654/43 Oct/Nov 2020

11 Ethene and propene are both members of the homologous series called the alkenes. Fig. 11.1 shows the structures of ethene and propene. H H H H C C C C H H H CH3 ethene propene Fig. 11.1 (a) State two reasons why ethene and propene are members of the same homologous series. reason 1 … … reason 2 … … [2] (b) Ethene can be made by the cracking of large alkane molecules. (i) State the conditions needed for cracking. 1 … 2 … [2] (ii) Ethene, C2H4, can be made by the cracking of octane, C8H18. The balanced symbol equation for the reaction is shown. C8H18 C4H10 + 2C2H4 State the name of the other product made and complete Fig. 11.2 to show its structure. Show all the covalent bonds. name … structure H C H Fig. 11.2 [3] (c) Ethene reacts with bromine, Br2, in an addition reaction. Write the balanced symbol equation for this reaction. … [2] (d) Propene forms poly(propene) in an addition polymerisation reaction. Complete the structure of poly(propene). H H C C H CH3 [1] (e) Nylon is a polymer made in a condensation polymerisation reaction. Complete the equation to show the formation of nylon. O O H H + H2N NH2 C C N N + 2H2O [1] [Total: 11]

11 marks

Mark scheme: 11(a) both have same functional group / both have (carbon to carbon) double bond ; both have same general formula / CnH2n ; both have similar (chemical) reactions ; trend in / similar, physical properties ; max 2 11(b)(i) high temperature / specified elevated temperature ; high pressure / specified elevated pressure ; catalyst / named catalyst ; AVP ; max 2 2 11(b)(ii) butane ; ;; 3 11(c) C2H4 + Br2 → C2H4Br2 C2H4Br2 ; then all else correct ; 2 Question Answer Marks 11(d) ; 1 11(e) ; 1

This question in 0654/41 May/June 2021

8 The fractional distillation of petroleum makes useful fractions. Three of the fractions made are petrol, fuel oil and refinery gas. Refinery gas contains ethane, C2H6. (a) Draw the structure of an ethane molecule. Show all the covalent bonds. [1] (b) Ethane burns in oxygen to make carbon dioxide and water. The balanced symbol equation is shown. 2C2H6 + 7O2 4CO2 + 6H2O The reaction is exothermic. Use the axes shown in Fig. 8.1 to draw and label the energy level diagram for this reaction. Label: • the energy of the reactants and the products • the energy change in the reaction • the activation energy of the reaction. energy progress of reaction Fig. 8.1 [3] (c) Fractional distillation makes too much fuel oil and not enough petrol. Cracking is a process that breaks large molecules into smaller molecules. Some fractions are cracked. Suggest why cracking is useful. … … … [2] (d) During cracking, dodecane, C12H26, can make octane, C8H18, and ethene, C2H4. Write the balanced symbol equation for this reaction. … [2] (e) Ethene is changed into poly(ethene) in a polymerisation reaction. Polymerisation changes many small molecules into larger long chain molecules. polymerisation small molecules larger long chain molecules State the name of the small molecules used in polymerisation. Choose from the list. alkane monomer nylon polymer … [1] (f) Fig. 8.2 shows the structure of a small molecule called propene. H H H H C C C H H Fig. 8.2 Propene is an alkene. It is unsaturated. Explain why propene is unsaturated. … [1] (g) Table 8.1 shows the structures of some small molecules and long chain molecules. Complete Table 8.1. Table 8.1 name of small structure of small molecule structure of long chain molecule molecule H H H H ethene C C C C H H H H n H H H C propene C C H H H H Cl chloroethene C C H H n [2] [Total: 12]

12 marks

Mark scheme: 8(a) ; 8(b) products shown below reactants ; energy change or correctly labelled ; activation energy correctly labelled ; 3 8(c) cracking makes more petrol / matches supply with demand ; cracking makes alkanes which can be used as fuels ; cracking makes alkenes which can be used to make plastics / alcohol / ethanol ; max 2 2 Activation Energy Energy Energy Change Question Answer Marks 8(d) C12H26 → C8H18 + 2C2H4 formulae ; balancing ; 2 8(e) monomer ; 1 8(f) (propene contains) a (carbon to carbon) double bond ; 1 8(g) (propene) (chloroethene) 2

This question in 0654/43 May/June 2021

5 Large hydrocarbon molecules can be cracked to make smaller molecules. The equation represents the cracking of hydrocarbon, C20H42. C20H42 C6H14 + 2C5H10 + 2C2H4 (a) State the formula of the product of the reaction which is an alkane. … [1] (b) Table 5.1 shows the boiling point, flammability and viscosity of C20H42 compared with the properties of C6H14, C5H10 and C2H4. Table 5.1 boiling point flammability viscosity A lowest lowest lowest B lowest highest highest C highest lowest lowest D highest lowest highest State which letter, A, B, C or D, shows how the properties of C20H42 compare with the properties of C6H14, C5H10 and C2H4. … [1] (c) The hydrocarbon C2H4 is burnt in air. Complete combustion occurs. Write the balanced symbol equation for this reaction. … [2] (d) Nylon is a polymer produced when monomers join together and release a small molecule. State the name of the small molecule released. … [1] (e) Poly(propene) is a polymer made from the monomer propene. Complete the equation to show the structure of poly(propene). CH3 H n C C C C H H [2] (f) Propene, C3H6, reacts with aqueous bromine. The balanced symbol equation for the reaction is shown. C3H6 + Br2 C3H6Br2 (i) Describe what is seen when propene reacts with aqueous bromine. … [1] (ii) Fig. 5.1 shows the energy level diagram for the reaction of propene with aqueous bromine. Complete the energy level diagram in Fig. 5.1. Include labelled arrows to show: • the energy given out • the activation energy. C3H6 + Br2 energy C3H6Br2 progress of reaction Fig. 5.1 [3] [Total: 11]

11 marks

Mark scheme: 5(a) C6H14 ; 1 5(b) D ; 1 5(c) C2H4 + 3O2 → 2 CO2 + 2H2O ;; 2 5(d) water ; 1 5(e) ;; 2 5(f)(i) (aqueous bromine is) decolourised / changes from orange or yellow to colourless ; 1 5(f)(ii) ;;; 3 activation energy energy given out

This question in 0654/42 Oct/Nov 2021

2 Chlorine and bromine are Group VII elements of the Periodic Table. Chlorine is more reactive than bromine. (a) State the names of the two products made when aqueous chlorine reacts with aqueous potassium bromide solution. … and … [2] (b) Chlorine reacts with hydrogen to form hydrogen chloride. Hydrogen chloride is a covalent compound. (i) Explain why hydrogen chloride is a gas at room temperature. Use ideas about structure and bonding. … … … [2] (ii) Hydrogen chloride gas dissolves in water to form dilute hydrochloric acid. Describe the effect of dilute hydrochloric acid on litmus paper. … [1] (iii) State the formula of the ion present in all acids. Choose from the list. Cl – H+ OH – O2– … [1] (c) A solution of dilute hydrochloric acid has a concentration of 73 g / dm3. Calculate the mass of hydrogen chloride in 250 cm3 of the solution. mass of hydrogen chloride = … g [2] (d) Bromine reacts with ethene. Fig. 2.1 shows the structures of the reactants and products in this reaction. H H H H C C + Br Br Br C C Br H H H H Fig. 2.1 (i) Put a circle around each of the bonds which are made when the reaction takes place. [1] (ii) When ethene reacts with bromine the reaction is exothermic. Explain why the reaction of ethene and bromine is exothermic. Use ideas about bond breaking and bond making. … … … [2] [Total: 11]

11 marks

Mark scheme: 2(a) potassium chloride ; bromine ; 2 2(b)(i) hydrogen chloride has weak intermolecular forces / weak attractions between (hydrogen chloride) molecules ; (weak intermolecular forces) take little energy to break / owtte ; 2 2(b)(ii) litmus paper turns red ; 1 2(b)(iii) H+ ; 1 2(c) mass of HCl in 250 cm³ = 73 250 1000 × OR 73 × 0.25 OR 73 ÷ 4 ; 18.25 (g) ; 2 2(d)(i) both C-Br bonds circled ; 1 2(d)(ii) bond breaking is endothermic / takes in energy and bond making is exothermic / gives out energy ; more energy is given out (during bond making) than is taken in (during bond breaking) / energy stored in product is less than energy stored in reactant ; 2

This question in 0654/43 Oct/Nov 2021

8 (a) Propene is an alkene. Put a tick (3) in the box next to the statement which describes alkenes. Alkenes are saturated polymers. Alkenes are saturated hydrocarbons. Alkenes are unsaturated polymers. Alkenes are unsaturated hydrocarbons. [1] (b) Propane is an alkane. Propane and propene are both gases. Describe a test to show which gas is propane. test … result with propane … result with propene … [3] (c) Propene is used to make poly(propene). Draw the bonds to complete the structures of propene and poly(propene) in Fig. 8.1. H CH3 H CH3 n C C C C H H H H n Fig. 8.1 [3] (d) Poly(propene) is made by addition polymerisation. Nylon is made by condensation polymerisation. Describe two differences between addition and condensation polymerisation. 1. . … … 2. . … … [2] [Total: 9]

9 marks

Mark scheme: 8(a) alkenes are unsaturated hydrocarbons ticked ; 1 8(b) test: aqueous bromine ; result with propane: no change / aqueous bromine stays orange or yellow ; result with propene: aqueous bromine is decolourised / aqueous bromine changes from orange or yellow to colourless ; 3 8(c) C=C in propene ; C—C in poly(propene) ; all else correct ; 3 8(d) addition polymerisation requires one monomer / condensation polymerisation requires two monomers ; addition polymerisation produces a polymer only / condensation polymerisation produces a polymer molecule and a small molecule ; 2

This question in 0654/43 Oct/Nov 2021

5 This question is about hydrocarbons. Fig. 5.1 shows the displayed formulae of three hydrocarbons. H H H H H H H H C C H H C C C H C C C H H H H H H H H H ethane propane propene Fig. 5.1 (a) The molecular formula of ethane is C2H6. Write down the molecular formula of propene. molecular formula = … [1] (b) Ethane and propane are members of the same group of hydrocarbons called the alkanes. State which group of hydrocarbons propene belongs to. … [1] (c) Propene is an unsaturated hydrocarbon. State what is meant by the word unsaturated. … … [1] (d) Propene can be changed into propane by reaction with hydrogen, as shown in Fig. 5.2. H H H H H C C C H + H2 H C C C H H H H H H H Fig. 5.2 State the name of this type of reaction. … [1] (e) Aqueous bromine is used to tell the difference between propene and propane. State what you would see when aqueous bromine is added to propene and propane. propene … propane … [2] (f) (i) Propene can be used as a monomer. Propene can be converted into a polymer, poly(propene), in an addition polymerisation reaction. Complete Fig. 5.3 to show the structure of poly(propene). H H C C Fig. 5.3 [2] (ii) Nylon is another polymer. Nylon is made in a condensation polymerisation reaction. Describe the differences between addition polymerisation and condensation polymerisation. … … … … [2] [Total: 10]

10 marks

Mark scheme: 5(a) C3H6 ; 1 5(b) alkenes ; 1 5(c) contains a carbon to carbon double bond ; 1 5(d) addition (reaction) / reduction / hydrogenation ; 1 5(e) propene (aqueous bromine) changes from orange to colourless / decolourised / loses its colour / owtte propane (aqueous bromine) stays orange / no change 2 Question Answer Marks 5(f)(i) ;; 2 5(f)(ii) any two from: condensation – one larger and one smaller molecule formed / addition – one large molecule formed ; in condensation polymerisation water is (often) produced (as the smaller molecule) ; AVP ; 2 CH3

This question in 0654/42 Feb/March 2022

11 Fig. 11.1 shows the structures of some compounds of carbon. H H H H H H C C C H H C C O H H H H H H compound A compound B H H H H H H H C C C C C C H H H H H compound C compound D Fig. 11.1 (a) State which compound A, B, C, or D is unsaturated. … [1] (b) State which one of these chemicals is used to test for unsaturation. aqueous barium chloride bromine limewater sodium hydroxide … [1] (c) Compound A is called propane. State the name of compound B. … [1] (d) Compound D is called poly(ethene). Poly(ethene) is a polymer made in an addition polymerisation reaction. (i) Complete the sentence to define a polymer. A polymer is a … … molecule formed from small units called … . [2] (ii) Draw the structure of the small unit (molecule) from which poly(ethene) is made. [1] (e) Fig. 11.2 shows the energy level diagram for the reaction between compound B and oxygen. reactants energy products progress of reaction Fig. 11.2 Energy is given out in this reaction. (i) Explain how Fig. 11.2 shows that energy is given out. … … [1] (ii) State the name of the type of reaction that gives out energy. … [1] (iii) Explain why energy is given out when compound B reacts with oxygen. Use ideas about bond breaking and bond making. … … … … [3] [Total: 11]

11 marks

Mark scheme: 11(a) C ; 1 11(b) bromine ; 1 11(c) ethanol ; 1 11(d)(i) long chain ; 2 monomers ; 11(d)(ii) 1 ; 11(e)(i) idea that products have less energy than the reactants ; 1 11(e)(ii) exothermic ; 1 11(e)(iii) bond breaking is endothermic / owtte ; 3 bond making is exothermic / owtte ; more energy is given out (in bond making) than is taken in (in bond breaking) ;

This question in 0654/42 Feb/March 2023

2 Alkanes are saturated hydrocarbons. (a) State what is meant by the term saturated hydrocarbon. … … … [2] (b) Alkenes are also hydrocarbons. Table 2.1 shows information about three alkenes. Complete Table 2.1. Table 2.1 name molecular formula structure H H C2H4 C C H H … propene C3H6 … H H H H C4H8 H C C C C H H H … [3] (c) Propane and propene are both colourless gases. Describe a test to show which gas is propane and which gas is propene. test … result with propane … … result with propene … … [3] (d) The monomer C4H8 in Fig. 2.1 can be used to make a polymer. H H H H H C C C C H H H Fig. 2.1 Complete Fig. 2.2 to show the structure of the polymer made. C C Fig. 2.2 [2] [Total: 10]

10 marks

Mark scheme: 2(a) (saturated) – contains only single (covalent) bonds ; (hydrocarbon) – contains only hydrogen and carbon atoms ; 2 Question Answer Marks 2(b) name molecular formula structure ethene ; C2H4 propene C3H6 ; butene ; C4H8 3 2(c) test – aqueous bromine ; result with propane – (aqueous bromine) stays orange / brown or no change ; result with propene – (aqueous bromine) is decolourised / turns colourless ; 3 Question Answer Marks 2(d) ;; 2

This question in 0654/42 May/June 2023

2 Crude oil contains hydrocarbon molecules. (a) State what is meant by a hydrocarbon. … … [1] (b) Alkanes are hydrocarbon molecules. (i) State the type of bond found in alkane molecules. Tick (3) one box. double covalent intermolecular ionic single covalent [1] (ii) Alkanes are saturated hydrocarbons. State which molecule is a saturated hydrocarbon. Tick (3) one box. C2H2 C2H4 C3H8 C4H8 [1] (c) Larger alkanes are cracked to form smaller alkanes and another type of hydrocarbon molecule. (i) State the name of this other type of hydrocarbon molecule. … [1] (ii) State the conditions needed for cracking. 1 … 2 … [2] (iii) The equation shows the cracking of C24H50. Balance the equation. [2] C24H50 C10H22 + … C6H12 + … (d) Hydrocarbon molecules are used as fuels. Burning fuels produce pollutants in the air. These pollutants cause problems. Draw one line from each pollutant to the problem it causes. pollutant problem acid rain carbon monoxide particulates turn buildings black global warming sulfur dioxide poisoning of living organisms [2] [Total: 10]

10 marks

Mark scheme: 2(a) (compound that) contains only carbon and hydrogen (atoms) ; 1 2(b)(i) single covalent ; 1 2(b)(ii) C3H8 ; 1 2(c)(i) alkene ; 1 2(c)(ii) high temperature ; 2 catalyst ; 2(c)(iii) C24H50 → C10H22 + 2 C6H12 + C2H4 2 correct number of C in products ; correct number of H in products ; 2(d) 2 pollutant problem acid rain carbon monoxide particulates turn buildings black global warming sulfur dioxide poisoning of living organisms correct link for carbon monoxide ; correct link for sulfur dioxide ;

This question in 0654/41 Oct/Nov 2023

8 Fig. 8.1 shows the structures of three carbon compounds. H H C C H H ethene H H H O H C C H C C O H O H H H H ethanoic acid ethanol Fig. 8.1 (a) Ethene is an unsaturated hydrocarbon. Explain how the structure of ethene shows that ethene is an unsaturated hydrocarbon. unsaturated … … hydrocarbon … … [2] (b) Ethene, C2H4, reacts with hydrogen to make an alkane. Write the balanced symbol equation for this reaction. … [2] (c) Complete the dot‑and‑cross diagram in Fig. 8.2 to show the bonding in ethene. Only show the outer‑shell electrons. H H C C H H Fig. 8.2 [2] (d) Ethanol is made by fermentation. State one condition for making ethanol by fermentation. … [1] (e) Ethanol can also be made from ethene in an addition reaction. Complete the symbol equation for this reaction. C2H4 + ……… C2H5OH [1] (f) A scientist makes a solution of ethanol. 250 cm3 of the solution contains 5.75 g of ethanol. Calculate the concentration of the ethanol solution in mol / dm3. [Ar: C, 12; H, 1; O, 16] concentration of ethanol solution = … mol / dm3 [4] [Total: 12]

12 marks

Mark scheme: 8(a) contains a double (carbon to carbon) bond ; contains only hydrogen and carbon (atoms) / AW ; 2 8(b) C2H4 + H2  C2H6 ;; 2 8(c) ;; 2 Question Answer Marks 8(d) absence of air / no oxygen / anaerobic / yeast / sugar or glucose / water / warm temperature ; 1 8(e) H2O ; 1 8(f) (Mr of C2H5OH) = 46 ; (moles of C2H5OH) = 5.75 ÷ 46 = 0.125 ; 250 cm3 = 250 ÷ 1000 = 0.250 dm3 ; (concentration of C2H5OH) = 0.125 ÷ 0.25 = 0.5 mol / dm³ ; 4

This question in 0654/42 May/June 2024

5 Fig. 5.1 shows the structures of four carbon compounds. H H H H H C C H C C H H H H A B H H H H H C C O H C C H H H H C D Fig. 5.1 (a) (i) State which compound is ethene. Choose from A, B, C or D. … [1] (ii) State which compound is an unsaturated hydrocarbon. Choose from A, B, C or D. … [1] (iii) Compound B is made from compound D. State what type of reaction takes place. … [1] (iv) Describe how compound C is made from compound D. … … [2] (v) Compound A is a member of a homologous series. State two similarities between the members of a homologous series. 1 … 2 … [2] (b) Fig. 5.2 shows the structure of a carbon atom. 6p 6n p = proton n = neutron = electron Fig. 5.2 (i) Carbon is in Group IV of the Periodic Table. Describe how to deduce from Fig. 5.2 that carbon is in Group IV. … … [1] (ii) Carbon exists as a mixture of isotopes. Complete Fig. 5.3 to show a different isotope of carbon from that shown in Fig. 5.2. Fig. 5.3 [3] [Total: 11]

11 marks

Mark scheme: 5(a)(i) D ; 1 5(a)(ii) D ; 1 5(a)(iii) addition polymerisation ; 1 5(a)(iv) addition of steam ; 2 using a catalyst ; 5(a)(v) general formula ; 2 chemical properties ; 5(b)(i) (carbon has) 4 electrons in the outer shell ; 1 5(b)(ii) diagram showing: 3 6 protons ; 6 electrons in the correct configuration of 2.4 ; any number of neutrons other than 6 ;

This question in 0654/42 Oct/Nov 2024

2 Fig. 2.1 shows the displayed formulae of some carbon compounds. H H H H C C H C C H H H H H A B H H H H H H C C C H H C C O H H H H H H C D Fig. 2.1 (a) State which compound in Fig. 2.1 is not a hydrocarbon. Explain your answer. compound … explanation … … … [2] (b) State which compound in Fig. 2.1 will decolourise aqueous bromine. … [1] (c) Compound D is used as a fuel. State one other use of compound D. … [1] (d) Compound C is a saturated compound. State what is meant by saturated. … … [1] (e) Compound C, C3H8, undergoes complete combustion in oxygen. Construct the balanced symbol equation for this reaction. … [2] (f) Compound A is ethene. Complete Fig. 2.2 to show the displayed formula of the polymer poly(ethene). C C Fig. 2.2 [1] (g) The formation of poly(ethene) from ethene is an example of addition polymerisation. Explain the differences between addition polymerisation and condensation polymerisation. … … … … [2] [Total: 10]

10 marks

Mark scheme: 2(a) D ; 2 contains oxygen / does not contain only carbon and hydrogen ; 2(b) A ; 1 2(c) solvent ; 1 2(d) contains only C-C single bonds ; 1 2(e) C3H8 + 5O2 → 3CO2 + 4H2O 2 correct formulae (reactants in either order and products in either order) ; balanced correctly ; 2(f) 1 2(g) addition polymerisation 2 only occurs in unsaturated monomers or monomers that contain C=C bonds / idea that involves the addition of many (identical) monomers (to make a long chained polymer) / monomers have one functional group / forms the polymer molecule only ; condensation polymerisation idea that two different monomers join together / (forms the polymer molecule and one) water molecule (per linkage) / monomers have two functional groups (one at each end) ;

This question in 0654/43 Oct/Nov 2024

7 The alkenes are a family of similar compounds with similar chemical properties. (a) State the term used to describe a family of similar compounds with similar chemical properties. … [1] (b) (i) Butene, C4H8, reacts with bromine. State what would be observed in the reaction. … … [2] (ii) The equation for the reaction is C4H8 + Br2 C4H8Br2 State what type of reaction this is. Choose your answer from the list. addition combustion cracking polymerisation answer … [1] (c) Butene also reacts with hydrogen to form butane, C4H10. C4H8 + H2 C4H10 Calculate the maximum mass of butane that can be made from 1.68 kg of butene. [Ar: C, 12; H, 1] mass of butane = … kg [3] (d) Fig. 7.1 shows the structural formula of but-1-ene. H H H H C C C C H H H H Fig. 7.1 Draw the structural formula of but-2-ene. [2] [Total: 9]

9 marks

Mark scheme: 7(a) homologous series ; 1 7(b)(i) orange / red-brown, bromine water ; 2 is decolourised / turns colourless ; 7(b)(ii) addition ; 1 7(c) Mr of C4H8 = 56 and Mr of C4H10 = 58 ; 3 58 Mass of C4H10 =  1.68 ; 56 = 1.74 (kg) ; 7(d) 2 ; ;

This question in 0654/42 Feb/March 2025

7 Look at the structures of the carbon compounds shown in Fig. 7.1. H H H Cl H H C C C C C H H H H n A B H H O H H O H H H C C O H C C N C C N H H H H n C D Fig. 7.1 (a) (i) State which compound is a hydrocarbon. Choose from A, B, C or D. … [1] (ii) State which compound is propene. Choose from A, B, C or D. … [1] (iii) State which compound is made from the reaction of ethene with steam in the presence of an acid catalyst. Choose from A, B, C or D. … [1] (iv) State which compound is made in a condensation polymerisation reaction. Choose from A, B, C or D. … [1] (b) Compound C, C2H5OH, completely combusts in oxygen. Construct the balanced symbol equation for the reaction. … [2] (c) A mixture containing 11.2 g of another carbon compound, C4H8, is allowed to react with 0.6 g of hydrogen, H2. C4H8 + H2 C4H10 Show, by calculation, that C4H8 is the limiting reactant. [Ar: C, 12; H, 1] C4H8 is the limiting reactant because … … [3] (d) Hydrogen, H2, is a simple covalent molecule. Complete the dot-and-cross diagram to show the bonding in a hydrogen molecule. H H [1] [Total: 10]

10 marks

Mark scheme: 7(a)(i) A; 1 7(a)(ii) A; 1 7(a)(iii) C; 1 7(a)(iv) D; 1 7(b) C2H5OH + 3O2 → 2CO2 + 3H2O 2 correct formulae; correct balancing; 7(c) moles of C4H8 = 11.2 = 0.2; 3 56 moles of H2 = 0.6 = 0.3; 2 (C4H8 is limiting because) 0.2 mol is less than the 0.3 mol of H2; 7(d) 1 ; ;

This question in 0654/43 May/June 2025

8 Petroleum is separated into useful fractions by fractional distillation. (a) Table 8.1 shows the boiling point range of three fractions obtained from petroleum. Table 8.1 fraction boiling point range / °C naphtha 90 to 200 refinery gas less than 25 diesel oil 150 to 380 State which fraction is obtained at the top of the fractionating column. … [1] (b) The diesel oil fraction can be cracked to make hydrocarbon molecules containing seven and eight carbon atoms. State which pair of hydrocarbon molecules would both turn aqueous bromine colourless. Tick (✓) one box. C7H14 and C8H18 C7H14 and C8H16 C7H16 and C8H16 C7H16 and C8H18 [1] (c) Another fraction obtained from crude oil is petrol. Petrol contains alkane molecules with the formula C9H20. (i) Complete the sentence about alkane molecules. The bonding between carbon atoms in alkanes is … covalent and alkanes are … hydrocarbons. [2] (ii) The equation for the complete combustion of petrol is shown. C9H20 + 14O2 9CO2 + 10H2O Calculate the maximum volume of carbon dioxide, in dm3 measured at room temperature and pressure, that is made from 6.4 kg of petrol. The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.). [Ar: C, 12; H, 1; O, 16] volume of carbon dioxide = … dm3 [3] (d) Refinery gas contains propane, C3H8. Draw a diagram to show the displayed formula of propane. [2] [Total: 9]

9 marks

Mark scheme: 8(a) refinery gas ; 1 8(b) C7H14 and C8H16 ; 1 8(c)(i) single ; 2 saturated ; 8(c)(ii) (moles of C9H20 = 6400 ÷ 128 =) 50 ; 3 (moles of CO2 = 9  50 =) 450 ; (volume of CO2 = 450  24 =) 10 800 (dm³) ; OR (mass of CO2 = (396 ÷ 128)  6400 =) 19 800 (g); (moles of CO2 = 19 800 ÷ 44 =) 450 ; (volume of CO2 = 450  24 =) 10 800 (dm³) ; 8(d) 2 chain of three carbons each joined by a single bond = 1 mark eight hydrogens joined to carbons by single bonds = 1 mark

This question in 0654/41 Oct/Nov 2025