NotesDownload Organic Chemistry MindmapDownload Organic Chemistry Notes (Credits to Mustafa Asif) Organic compounds:
Characteristics of Organic Compounds
Some uses of Organic Compounds
Classifying Organic CompoundsHomologeous series: a family of organic compounds with a general formula and a similar chemical propertiesFunctional Groups
Production of Organic Compoundsa. From crude oil refinery:
b. From naphtha:
Saturated vs UnsaturatedSaturated hydrocarbons
Unsaturated hydrocarbons
AlkanesCharacteristics
Structure of Alkanes
Physical Properties of Alkanes
Reaction of Alkanes
1) Combustion
2 C4H10 (g) + 13 O2 (g) --> 8 CO2 (g) +10 H2O (l)
2) Reaction with Chlorine/Other Halogens (Alkyl Halides)
AlkenesCharacteristics- have general formula CnH2n.- all alkene names end with –ene. - the formula of one alkene differs from the next by –CH2. - have similar properties like alkane going down the series. Structure of Alkenes
The Importance of EtheneEthanol – solvent & fuelPoly(ethene) – PE plastic variations Ethanoic acid – vinegar Reactions of Alkenes1) Combustion
C2H4 (g) + 3O2 (g) --> 2CO2 (g) + 2H2O (l)
2) Addition Reaction
3) Polymerization
Testing for Unsaturated Compounds
Characteristics of a Homologous Series
The Manufacture of Margarine
The Cracking of Alkanes
E.g. Octane can be cracked into simpler hydrocarbons such as the reaction below. Suggest the possible identity of product x. C8H18 (l) --> C2H4 (g) + x + CH4 (g) Number of C atoms in x = 8 – 2 – 1 = 5 Number of H atoms in x = 18 – 4 – 4 = 10 ---> Product x is C5H10 Isomers
AlcoholsCharacteristics
- Ethanol, C2H5OH or CH3CH2OH - Propanol, C3H7OH or CH3CH2CH2OH
Making Ethanol1. Fermentation of sugars with yeast2. Reacting ethene with steam 1. Fermenting glucose
2. Reacting Ethene with Steam
Uses of Alcohol
REACTIONS OF ALCOHOL1) Combustion
E.g. combustion of ethanol C2H5OH (aq) + 3O2 (g) --> 2CO2 (g) + 3H2O (l) Example: 2) Oxidation a. Alcohol can be prepared in laboratory by warming alcohol with oxidizing agent (e.g. acidified potassium chromate(VI)).
E.g. oxidation of ethanol produces water and ethanoic acid C2H5OH (aq) + 2[O] {from oxidizing agent} ---> 2CH3COOH (g) + 3H2O (l) 2. Alcohol can be oxidized when left in air with bacterial enzymes as catalyst.
E.g. ethanol produces water and ethanoic acid when left in air. C2H5OH (aq) + O2 (g) ---> 2CH3COOH (aq) + 3H2O (l) 3) Esterification Carboxylic AcidsCharacteristics
- Ethanoic acid, CH3COOH - Propanoic acid, C2H5COOH --> Propanoic acid PREPARATION OF CARBOXYLIC ACIDS1. From natural gas
E.g. production of ethanoic acid from methane 2CH4 (g) + 2O2 (g) ---> CH3COOH (aq) + 2H2O (l) 2. Oxidation PROPERTIES OF CARBOXYLIC ACIDS
E.g. Reaction between calcium and ethanoic acid forming calcium ethanoate and hydrogen Ca (s) + 2CH3COOH (aq) ---> Ca(CH3COO)2 (aq) + H2 (g)
E.g. Ethanoic acid reacts with sodium hydroxide to form sodium ethanoate and water. CH3COOH (aq) + NaOH (aq) ---> CH3COONa (aq) + H2O(g)
E.g. Ethanoic acid reacts with sodium carbonate to form sodium ethanoate and water. 2CH3COOH (aq) + Na2CO3 (aq) ---> 2CH3COONa (aq) + CO2 (g) + H2O (g) ESTERIFICATION
Synthetic Macromolecules
ADDITION POLYMERISATIONa. From monomer to polymerExample: Formation of poly(ethene) from ethene
CONDENSATION POLYMERISATION
Nylon --> Dicarboxylic acid and diamine undergo condensation polymerisation to form nylon.
- make tents and parachutes due to strength - fishing lines - rugs and carpets Terylene --> Dicarboxylic acid (acid with 2 –COOH groups) and diol (alcohol with 2 –OH groups) undergo condensation polymerisation to form terylene
PROBLEMS ASSOCIATED WITH PLASTICS
Natural Macromoleculesa. Carbohydrates
b. PROTEINS
c. FATS
MCQ1. Which physical property of the alkanes does not increase as relative molecular mass increase?a. boiling point b. flammability c. melting point d. viscosity 2. In the polymerization of ethene to form polyethene, there is no change in a. boiling point b. density c. mass d. molecular formula 3. Which polymer has the same type of linkage between its monomers as in a fat? a. polyamide b. polyester c. protein d. starch 4. Cholesterol is an organic molecule that occurs in the blood stream. Which type of compound is cholesterol? a. acid b. alcohol c. alkane d. alkene 5. Which of the following can best be used to distinguish between ethane and ethene? a. lighted splint b. aqueous bromine c. limewater d. litmus solution 6. Methane is used as a fuel. What property is essential for this use? a. it burns exothermically b. it is a gas c. it is odourless d. it has a low boiling point 7. All the members of a homologous series have the same a. empirical formula b. general formula c. molecular formula d. physical properties 8. Yeast can be used to convert simple sugars to a. ethanoic acid and oxygen b. ethanol and carbon dioxide c. ethanol and oxygen d. starch and carbon dioxide 9. Which type of reaction occurs when soap is formed from fats? a. hydrolysis b. polymerisation c. fermentation d. substitution 10. Octane is an alkane present in petrol. What are the products when octane is completely burned in air? a. carbon dioxide and hydrogen b. carbon dioxide and water c. carbon monoxide and water d. carbon monoxide, carbon dioxide, and water 11. Which compound, on combustion, never forms soot. a. carbon monoxide b. ethanol c. ethene d. methane 12. What is produced when ethanol is boiled with an excess of acidified potassium dichromate(VI)? a. ethane b. ethanoic acid c. ethene d. ethyl ethanoate 13. Which of the following is not made from crude oil? a. aircraft fuel b. diesel oil c. furniture polish d. margarine 14. Which of the following is an ester? a. pvc b. soap c. starch d. terylene 15. Starch can be broken down into smaller molecules by heating with a dilute acid. What is this type of reaction called? a. cracking b. fermentation c. hydrolysis d. reduction 16. A margarine is described as 'high in polyunsaturates'. What does this type of margarine contain? a. long chain alkane molecules b. many alkene molecules joined by addition polymerization c. molecules containing many C=C bonds d. polymer molecules with -O=C-N-H- linkages 17. Vinegar is a solution of ethanoic acid made by the reaction of ethanol with air. Which gas in air takes part in this reaction? a. carbon dioxide b. nitrogen c. oxygen d. water vapour 18. When must a substance be an alkane? a. when it burns easily in air or in oxygen b. when it contains carbon and hydrogen only c. when it has the general formula CnH2n+2 d. when it is generally unreactive 19. One mole of a hydrocarbon X reacted completely with one mole of hydrogen gas in the presence of a heated catalyst. What could be the formula of X? a. C2H6 b. C3H8 c. C5H10 d. C7H16 20. Nylon (a polyamide) and Terylene (a polyester) are both man-made fibres. Which type of reaction is used to produce both of these polymers? a. addition b. condensation c. fermentation d. hydrolysis 21. Part of a polymer molecule has the following structure. -CH2-CH2-CH2-CH2-CH2-CH2- From which substance is this polymer made? a. C2H4 b. C2H6 c. C3H6 d. C3H8 22. What type of reaction occurs when soap is formed from fats? a. hydrolysis b. polymerization c. fermentation d. substitution 23. Which of these equations does not represent an addition reaction? a. CH2Cl2 + Cl2 --> CHCl3 + HCl b. C2H4 + Br2 --> C2H4Br2 c. nC2H4 --> -(CH2 - CH2)n- d. C3H6 + H2O --> C3H7OH 24. Which set contains all the possible combustion products of methane, CH4? a. carbon, carbon dioxide, carbon monoxide, water b. carbon, carbon monoxide, hydrogen c. carbon dioxide, carbon monoxide, hydrogen, water d. carbon monoxide, water 25. Octane is an alkane containing eight carbon atoms per molecule. What is its molecular formula? a. C8H14 b. C8H16 c. C8H18 d. C8H20 26. What is produced when ethanol is boiled with an excess of acidified potassium dichromate(VI)? a. ethane b. ethanoic acid c. ethene d. ethyl ethanoate 27. What is the linkage between the units in fats and also in Terylene? 28. The structure of butan-1-ol is shown. Which structure is an isomer of that shown above? 29. The structures of an acid and an alcohol are shown. Which pairing of names correctly identify the two compounds? acid alcohol a. ethanoic butanol b. ethanoic propanol c. propanoic propanol d. propanoic butanol 30. The structure of four organic compounds are shown. Which compounds decolorise bromine water? a. 1 and 2 b. 1, 2, and 4 c. 2 and 4 d. 3 and 4 31. Which polymer has the empirical formula CH? 32. Which is the structure of ethyl ethanoate? 33. The structures of three compounds P, Q and R are shown. Which compounds are isomers of each other? a. P and Q only b. P and R only c. Q and R only d. P, Q and R 34. The structural formula of butenedioic acid is shown. Which statement about butenedioic acid is not correct? a. it decolorises aqueous bromine b. its aqueous solution reacts with sodium carbonate c. its empirical formula is the same as its molecular formula d. its relative molecular mass is 116 35. The diagram represents an organic compound that contains three different elements What could be the compound? a. ethanoic acid b. ethanol c. propane d. propene 36. Which of the following reacts with sodium carbonate to produce carbon dioxide? 37. A polymer has the structure shown. What is the molecular formula of the monomer? a. C2H4 b. C2H6 c. C3H6 d. C3H8 38. The structure of the monomer of Perspex is shown. Which description of Perspex is correct? type of polymer polymer formed by a. carbohydrate condensation polymerization b. ester addition polymerization c. hydrocarbon addition polymerization d. polyester condensation polymerization 39. Which of the following describes the ways in which isomers are identical and different? identical different a. chemical properties molecular formulae b. molecular formulae structures c. physical properties chemical properties d. structure molecular formulae 40. When an animal fat is boiled with aqueous sodium hydroxide, a soap and glycerol are formed. This reaction is an example of a. esterification b. fermentation c. hydrolysis d. polymerization 41. In which chemical reaction does the named product formed have a lower molecular mass than the reactant? a. formation of an ester from ethanol b. formation of ethanoic acid from ethanol c. formation of ethanol from glucose d. formation of ethanol from glucose 42. In the polymerisation of ethene to form poly(ethene), which does not change? a. boiling point b. density c. empirical formula d. molecular mass 43. Why are large alkane molecules cracked to form smaller molecules? a. alkanes with large molecules are not useful b. small alkane molecules can be polymerised c. crude oil does not contain small alkane molecules d. to meet the demand for small alkane molecules 44. What is the catalyst used in the preparation of ethyl ethanoate from ethanol and ethanoic acid? a. concentrated sulphuric acid b. nickel c. vanadium(V) oxide d. yeast 45. Which of these polymers is a protein? a. (C2H3Cl)n b. (C2H3NO)n c. (C5H8O2)n d. (C6H10O5)n a. carbon b. hydrogen c. oxygen d. sodium 47. Which statement is true about ethanol? a. it is formed by the catalytic addition of steam to ethene b. it is an unsaturated compound c. it is formed by the oxidation of ethanoic acid d. it reacts with ethyl ethanoate to form an acid 48. Which compound has the empirical formula CH2O and reacts with sodium hydroxide? a. ethanoic acid b. ethanol c. ethyl ethanoate d. methanoic acid 49. Cholesterol is an organic molecule that occurs in the blood stream. What type of compound is cholesterol? a. acid b. alcohol c. alkane d. alkene 50. X Y Z a. respiration reduction acidification b. respiration oxidation hydrogenation c. cracking oxidation neutralisation d. combustion oxidation esterification 51. Cracking is a common process in the petroleum industry. Which of the following gives the most appropriate explanation for carrying out cracking? a. It forms more useful fractions for commercial use. b. There is too much of the heavier fraction of petroleum present. c. It is easier to form useful fuel fractions through this means than through fractional distillation of petroleum. d. The reaction is exothermic. MCQ Answers1. b2. c 3. b 4. b 5. b 6. a 7. b 8. b 9. a 10. b 11. a 12. b 13. d 14. d 15. c 16. c 17. c 18. c 19. c 20. b 21. a 22. a 23. a 24. a 25. c 26. b 27. a 28. d 29. d 30. c 31. d 32. b 33. d 34. c 35. b 36. b 37. c 38. b 40. c 41. d 42. c 43. d 44. a 45. b 46. d 47. a 48. a 49. b 50. d 51. a Structured Question Worked Solutions1. Ethyl ethanoate is made by esterification.ethanoic acid + ethanol <--> ethyl ethanoate + water The table below gives the relative molecular masses for the reactants and products in the reaction.
a. In an experiment, 3.0g of ethanoic acid and 4.6g of ethanol were heated together with a catalyst. i. how many moles of ethanoic acid were used? ii. how many moles of ethanol were used? iii. which reactant (ethanol or ethanoic acid) was in excess? iv. what mass of ethyl ethanoate would be made if there was 100% conversion? v. in an experiment, only 2.20g of ethyl ethanoate were obtained. What was the percentage yield of ethyl ethanoate? b. Propanoic acid has the following structural formula. Draw the structural formula of the ester formed when propanoic acid reacts with ethanol. Solution 1ai. amount of acid used = 3.0/60 = 0.05 mole 1aii. amount of ethanol used = 4.6/46 = 0.1 mole 1aiii. ethanol 1aiv. amount of ester produced = 0.05 mole mass of ester produced = 0.05 x 88 = 44 g 1av. % yield = 2.20/4.4 x 100% = 50% 1b. 2. Ethanol, C2H5OH is used in Brazil as a liquid fuel instead of gasoline (petrol). The ethanol is manufactured by a fermentation process from sugar cane. ai. describe how cane sugar can be converted into ethanol by the process of fermentation. aii. what is the name of the gas produced during this fermentation? How would you test for this gas? b. When ethanol is completely burnt in air, it forms carbon dioxide and water. One mole of ethanol will release 1370 kJ of heat energy during this reaction. i. Construct the balanced equation for the burning of ethanol. ii. The mass of 1 litre of ethanol is 780 g. How much heat energy will be released when 1 litre (1dm3) of ethanol is completely burnt? c. When completely burnt, 1 litre of gasoline releases 38000 kJ of heat energy. Comparing ethanol and gasoline as liquid fuels, suggest i. one advantage of using ethanol rather than gasoline ii. one advantage of using gasoline rather than ethanol Solution 2ai. A mixture of sugar cane (which contains glucose) with some yeast is allowed to ferment in a closed container in the absence of air for some time. C6H12O6 --(yeast)--> 2C2H5OH + 2CO2 2aii. carbon dioxide. This gas can be tested by passing it through limewater and the solution turns milky (white precipitate formed) 2bi. C2H5OH (l) + 3O2 (g) --> 2CO2 (g) + 3H2O (l) 2bii. Mr of ethanol = 2 x 12 + 6 x 1 + 16 = 46 amount of ethanol used = 780/46 moles amount of energy released = 780/46 x 1370 = 23230 kJ 2ci. Burning ethanol produces less carbon dioxide, which is one of the components responsible for the Greenhouse effect. 2cii. Burning gasoline produces more energy. 3. The following questions refer to compounds with the structures drawn below. Using the letters A to F as appropriate, answer the following. a. Which compound is an unsaturated hydrocarbon? b. Which compounds are members of the same homologous series? c. Which compound reacts with sodium carbonate? d. Which compounds are isomers of each other? Solution 3a. E 3b. B, F 3c. C 3d. A, D 4. Olive oil contains oleic acid which is unsaturated. ai. By naming the reagent and giving the observation, describe a simple test to confirm that olive oil contains an acid. aii. Explain what is meant by unsaturated aiii. By naming the reagent and giving the observation, describe a simple test to confirm that oleic acid is unsaturated. b. The molecular formula of oleic acid is C17H31CO2H. How many double bonds between carbon atoms are present in one molecule of oleic acid? Explain your answer. Solution 4ai. reagent: sodium carbonate observation: effervescence. Gas turns limewater milky. 4aii. An unsaturated compound is one that contains multiple bonds eg double bonds 4aiii. reagent: bromine observation: the brown color of bromine is discharged 4b. number: 2 Explain: If oleic acid does not contain C=C double bond, its formula should be C17H35CO2H (CnH2n+1CO2H). Since its formula has 4 hydrogen less than 33, it should therefore contain 2 double bonds. 5. The structure of fluorochloroethane is shown below a. Suggest a name for, and sketch the structure of, the macromolecule formed when fluorochloroethene polymerizes. b. When 20 tonnes of fluorochloroethene polymerised, 18 tonnes of the polymer were obtained. Calculate the percentage yield. c. Name and give a use for a commercially available polymer containing a halogen. Solution 5a. poly(fluorochloroethene) 5b. Theoretically, 20 tonnes of products should be obtained. Therefore % yield = 18/20 x 100% = 90% 5c. polyvinylchloride (PVC). It is used as plastics. 6. Ethyne, C2H2, burns in oxygen to give a very hot flame. The temperature is so high that the flame can be used to cut metal. ai. Name the two products of the complete combustion of ethyne. aii. Describe a chemical test for one of these products b. Calcium carbide, CaC2, is a greyish-white solid. Ethyne can be made by the reaction of calcium carbide with water. Calcium hydroxide, Ca(OH)2 is the other product of the reaction. i. Construct an equation, including state symbols, for the reaction between carlcium carbide and water. ii. The mixture obtained after this reaction was tested using Universal Indicator. What was the final color of the Universal Indicator? Explain your answer. Solution 6ai. carbon dioxide and water 6aii. Bubble the gas through limewater. A white precipitate would be observed 6bi. CaC2 (s) + 2H2O (l) --> Ca(OH)2 (aq) + C2H2 (g) 6bii. Blue. Ca(OH)2 is alkaline. 7a. The following terms are used in the description of organic compounds. alcohol amide alkane hydrocarbon alkene polymer From this list, choose two terms which can be applied to each of the compounds below. i. methane ii. hexene iii. poly(ethene) iv. nylon b. One of the general characteristics of homologous series is that all the members can be represented by a general formula. i. What is the general formula of the alkene series? ii. Give one other general characteristics of homologous series. Solution 7ai. alkane, hydrocarbon 7aii. alkene, hydrocarbon 7aiii. alkane, polymer 7aiv. amide, polymer 7bi. CnH2n 7bii. The members show similar chemical reactions. 8a. Heptane is an alkane with seven carbon atoms per molecule. It is a colorless liquid with a boiling point of 100ºC. i. deduce the molecular formula of heptane ii. suggest two tests you could use to decide whether a colorless liquid was heptane or water. Predict the results of the tests for both heptane and water. b. Fructose is a carbohydrate. One form of fructose has the following structure. i. deduce the molecular formula of fructose ii. suggest why the term 'carbohydrate' is used for this type of compound iii. name another carbohydrate Solution 8ai. C7H16 8aii. test 1: add anhydrous copper(II) sulphate heptane: solid copper(II) sulphate remains white and insoluble water: solid turns blue and then dissolves to give a blue solution test 2: ignite with a flame heptane: burns with a luminous flame water: the flame dies off 8bi. C6H12O6 8bii. The molecular formula seems to suggest 6 units of carbon, and hydrogen and oxygen in the ratio 2:1 just like water C6(H20)6 ie. hydrate of carbon. 8biii. glucose 9a. Hydrogen can be manufactured by the reaction between methane and steam. i. Name a source of the methane required for this reaction. ii. Give the equation for this reaction between methane and steam. iii. Calculate the maximum volume of hydrogen, measured at r.t.p. which can be obtained from 16g of methane. b. Margarine is manufactured using the addition reaction between hydrogen and a vegetable oil. i. state the conditions used for this reaction ii. what type of bond must be present in the vegetable oil for this reaction to take place? c. The diagram represents the structure of a common plastic. i. Name this plastic and draw the structure of the monomer from which it is made. ii. This plastic is non-biodegradable. Explain the meaning of this term and describe the problems which this property creates. d. If this plastic is burned, a thick, black smoke and a very acidic gas are produced. i. suggest the identity of the black particles in the smoke ii. suggest the identity of the very acidic gas. Solution 9ai. natural gas 9aii. CH4 (g) + H2O (g) --> CO (g) + 3H2 (g) 9aiii. Mr of CH4= 16 amount of CH4 = 16/16 = 1 mol amount of H2 formed = 3 mol volume of 1 mole of gas at r.t.p. = 24dm3 volume of H2 formed = 3 x 24 = 72 dm3 at r.t.p. 9bi. Nickel catalyst, high pressure 9bii. double bonds 9ci. polyvinylchloride (PVC) 9cii. Non-biodegradable means cannot be broken down by biochemical reactions by bacteria. 9di. carbon 9dii. hydrogen chloride 10. Ethene is an unsaturated hydrocarbon. ai. what is meant by 'unsaturated'? b. Ethene is made by the cracking of long chain hydrocarbon molecules such as C16H34. Construct an equation to illustrate the cracking of C16H34 to make ethene and another hydrocarbon as the only products. c. Ethene is bubbled through aqueous bromine to form 1,2-dibromoethane. What would you observe during the reaction? d. Give the name of the product and the conditions needed for the reaction of ethene with water. e. Calculate the volume of carbon dioxide, measured at r.t.p., produced by the complete combustion of 1.40g of ethene. f. Ethene can be made into poly(ethene). Draw the structure of poly(ethene). Solution 10a. An unsaturated compound is one that contains multiple bonds eg C=C 10b. C16H34 --> 3C2H4 + C10H22 10c. Decolorization of brown bromine 10d. C2H4 (g) + 3O2 (g) --> 2CO2 (g) + 2H2O (l) Mr of C2H4 = 28 25g of C2H4 give 48 dm3 of CO2 at r.t.p. --> 1.40g of C2H4 give 1.40 x 48/28 = 2.4dm3 of CO2 at r.t.p. 10f. 11. The following is a list of formulae of organic compounds. CH3COOH C5H12 C2H5OH C3H6 C7H14 Which of the above formula fit the following descriptions? a. a compound which dissolves in water to form an acidic solution b. a compound which is not a hydrocarbon c. two compounds which are from the same homologous series d. two compounds which react to form an ester e. a compound which undergoes an addition reaction with steam f. a compound which is oxidised by acidified potassium dichromate(VI) to give ethanoic acid Solution 11a. CH3COOH 11b. CH3COOH or C2H5OH 11c. C3H6 or C7H14 11d. CH3COOH and C2H5OH 11e. C3H6 or C7H14 11f. C2H5OH 12. Ethanol, CH3CH2OH is a liquid fuel. Ethanol can be manufactured either from glucose C6H12O6 or from ethene. a. Briefly describe the manufacture of ethanol from glucose. Include the balanced equation in your answer. bi. Draw the displayed formula for ethene bii. Name the substance that reacts with ethene to make ethanol biii. Give the conditions needed for this reaction. Solution 12a. Yeast cells are added to a solution of glucose. The mixture is kept at 18-20ºC under anaerobic conditions. Glucose will be broken down by zymase enzyme in yeast cells to form ethanol and carbon dioxide. Ethanol is obtained by fractional distillation of the mixture. C6H12O6 --> 2C2H5OH + CO2 12bi. 12bii. steam 12biii. 300ºC, 70 atmospheric pressure and phosphoric acid catalyst 13. Styrene-butadiene rubber is a synthetic rubber. It is made by polymerising a mixture of the monomers butadiene and styrene. a. What type of polymerization will take place when the monomers polymerise? Explain. One possible structure for the polymer is shown below. b. Give the full structural formula for the repeating unit in this polymer structure. c. When the mixture of styrene and butadiene polymerises, the polymer is unlikely to contain only this regular, repeating pattern. Explain why. Butadiene can be made by cracking butane in a cracking tower. di. Butane cracks to form butadiene and one other product. Write an equation to show this reaction. dii. Give a use of the other product of this reaction. e. 2.90kg of butane entered the cracking tower. After the reaction, 2.16kg of butadiene had been made. Calculate the percentage yield of butadiene. Solution 13a. Addition polymerization. Addition polymerization is the joining together of two or more simple molecules, called monomers, to form a long chain compound without any loss of small molecules. The addition polymerization process can only occur when the monomer molecule is unsaturated (contain double bonds or triple bonds) 13b. ![]() 13c. Since two different monomers are mixed together before being polymerized the chain will have the different monomers distributed randomly along its length. Let styrene monomer be A and butadiene monomer be B. One possible random distribution is -A-A-B-A-B-B-A-B-A-A-B-B-B-A- Sometimes the same type of monomers may be polymerised to form short chains and then these chains mixed and further addition polymerization occurs. For eg. -A-A-A-A-A-A-A-B-B-B-B-B-B- 13di. hydrogen gas 13dii. used in the manufacture of ammonia in the Haber process 13e. Mr of butane = 58 Mr of butadiene = 54 no. of moles of butane = 2900/58 = 50 From the eq, 1 mol of butane undergoes cracking to form 1 mol of butadiene. no. of mole of butadiene formed = 50 mass of butadiene = 50 x 54 = 2700g --> 2.7kg experimental yield of butadiene = 2.16kg % yield of butadiene = 2.16/2.7 x 100 = 80% 14. This is the structure of an ester made in a reversible reaction between a carboxylic acid and an alcohol. ai. State the conditions for this reaction aii. Draw the structure of the carboxylic acid used in the reaction. aiii. Write an equation for this reaction. b. A student carried out some experiments to compare the relative strengths of dilute ethanoic acid with dilute hydrochloric acid. i. Describe a test that can be used to distinguish between dilute ethanoic acid and dilute hydrochloric acid. ii. Explain, using ideas about ions, why the two acids behave differently. iii. Name a solid substance that will react with both acids. Describe what you will see during the reaction. Solution 14ai. Heat the carboxylic acid with alcohol ethanol using a few drops of concentrated sulphuric acid as catalyst. 14aii. 14aiii. CH3COOH +C3H7OH --> CH3COOC3H7 + H2O 14bi. Place about 2cm3 of each acid in separate test tubes. Add a few drops of silver nitrate solution to each test tube. A white precipitate will be observed in the test tube containing hydrochloric acid. 14bii. Dilute hydrochloric acid is a strong acid and ethanoic acid is a weak acid. Dilute HCl dissociates fully in water whereas a weak acid dissociates partially in water to form hydrogen ions, H+ HCl (aq) --> H+ (aq) + Cl- (aq) Ethanoic acid dissociates partially in water to form a solution containing H+ ions. There are more acid molecules in a solution of weak acid than H+ ions. CH3COOH <--> CH3COO- + H+ 14biii. solid calcium carbonate. observations: Effervescence occurs. Colorless, odourless gas formed white precipitate with limewater. |
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