1. Organic Chemistry Structures 1

2. What do I need to know? 1.Translate between molecular, structural and ball and stick representations of simple organic molecules 2.Describe how the functional group affects the property of an organic compound and understand that alkanes are unreactive towards aqueous reagents because C—C and C—H bonds are unreactive; 3.Write balanced chemical reactions including for burning hydrocarbons including state symbols 2

3. Representations of organic molecules There are a number of different ways to represent organic molecules. Ball and stick – this is just like molymods 3

4. Representations of organic molecules Structural formula – this is where we show the covalent bonds between atoms as a line Semi-structural (molecular) – this is where we write out the formula but do not include bonds; these are implied eg CH 3 CH 2 OH 4

5. Molecular formula – this simply counts the numbers of each sort of atom present in the molecule, but tells you nothing about the way they are joined together. Eg C 2 H 6 O This is the least helpful type of formula as it could be one of two (or more) different chemicals 5

6. Example question 6

7. Mark scheme 7

8. Rules of organic molecules Generally speaking Carbon must make four bonds Nitrogen must make three bonds Oxygen must make two bonds Hydrogen must make one bond A double bond counts as two bonds eg C=C or C=O. A triple bond counts as three bonds. 8

9. AfL - Quiz 1.Draw the structural formula for butanol 2.Write the molecular formula for butanol 3.Draw the structural formula for hexane 4.Write the molecular formula for hexane 5.Write the molecular formula for an alkane with 25 carbon atoms. 6.How many bonds does oxygen make in methanol? 7. Give an example of a use for ethanol 8. Give an example of a use for methanol 9

10. 1.Butanol 2.C 4 H 10 O 3.Hexane 4.C 6 H 14 5.C 25 H 52 6.2 7.Fuel/feedstock for synthesis/solvent/used in perfume 8.Solvent, antifreeze, feedstock for adhesives and plastics 10

11. Understanding reactivity Alkanes are unreactive towards aqueous reagents because C-C and C-H bonds are unreactive. What about organic molecules that have different bonds? We call families of different types of bonded atoms FUNCTIONAL GROUPS An example is the –OH group or alcohol group. 11

12. Different functional groups NameFunctional groupProperties AlkaneC-HRelatively unreactive, burns in air due to hydrocarbon chain AlkeneC=CUsed as a feedstock to make polymers Alcohol-OHGood solvent, volatile, burns in air due to hydrocarbon chain Carboxylic acid-COOHWeak acid such as vinegar EsterRCOOR’Have distinctive smells such as fruits 12

13. Alkanes and combustion Because of the hydrocarbon chain alkanes burn readily releasing large amounts of energy. Alkanes are therefore used as fuels. When they burn completely they make carbon dioxide and water. eg octane (found in petrol) C 8 H 18 +12 ½ O 2  8CO 2 + 9H 2 O 13

14. Example question 14

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16. Example question 16

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18. Balanced chemical equations Write the balanced chemical equation for burning ethanol in air as a fuel and burning pentane as a fuel (include state symbols). 18

19. Answers Ethanol 2C 2 H 5 OH(l) + 6O 2 (g)  4CO 2 (g) + 6H 2 O(l) Pentane C 5 H 12 (l)+ 8O 2 (g)  5CO 2 (g) + 6H 2 O (l) 19

20. Example questions 20

21. Mark scheme 21

22. Alcohols and the Manufacture of Ethanol C7.1 and C7.5 22

23. What do I need to know? 1. The characteristic properties of alcohols are due to the presence of an –OH functional group 2. Know a range of methods for synthesising ethanol and limitations of fermentation reactions 3. Be able to explain why bioethanol is important for sustainability 23

24. Functional groups - reminder Look back at your table of functional groups. Write a short paragraph to explain why different organic chemicals have different properties in terms of functional groups. Use examples such as “carboxylic acids are acidic because they have a –COOH group”. 24

25. Can you recognise the functional group? Circle which of these are alcohols? 25

26. Answer Alcohols have an –OH group 26

27. Properties and uses of alcohols Properties: volatile liquid (evaporates quickly at room temperature – more than water) colourless burns readily in air because of the hydrocarbon chain good solvent 27

28. Example question 28

29. Mark scheme 29

30. Uses of ethanol and methanol Ethanol: biofuels, solvents, feedstock for synthesis Methanol: cleaner, feedstock for synthesis Feedstock is the name we give to an “ingredient” on a chemical plant 30

31. Reactions of different functional groups This is illustrated very well by comparing the reaction of sodium with ethanol, hexane and water. You have seen this reaction. Fill in the following table and compare with the mark scheme: 31

32. Observations with sodium 32

33. Mark scheme 33

34. Comparing functional groups 34

35. Mark scheme 35

36. How do we make ethanol? Fermentation is a key process for obtaining ethanol. It is relatively cheap and requires wheat or beet sugar. The process involves the anaerobic respiration of yeast at temperatures between 20 and 40°C and at pH 7. 36

37. Conditions for fermentation 37

38. Example question 38

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40. Example question 40

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42. Example question 42

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44. How do we obtain a concentrated solution? Ethanol has a different boiling point to water. We can therefore separate water and ethanol using distillation. 44

45. Example question 45

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47. Making ethanol using ethane from crude oil Ethane to ethene by CRACKING C2H6  CH2=CH2 zeolite catalyst OR heat Ethene to ethanol by reaction with STEAM CH2=CH2 + H 2 O  CH3CH2OH phosphoric acid catalyst 47

48. Example question 48

49. Mark scheme 49

50. Working out masses We can use the useful relationship Where Mr is the molecular mass eg Mr of ethane C 2 H 6 is (2 X 12) + (6 x 1) = 30 50

51. Example question 51

52. Explanation In this question every ethene molecule that reacts makes one molecule of ethanol. We need to relate the number of molecules to mass using our equation. Mass 1 is mass of ethene = 1 tonne Mr 1 is Mr of ethene = 28 Mass 2 is mass of ethanol = ? Mr 2 is Mr of ethanol = 46 52

53. Mark scheme 53

54. Example question 54

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56. Other alternatives Ethanol has also been synthesised using genetically modified e-coli bacteria and sugars from seaweed. This process is sustainable as the seaweed and bacteria are renewable sources Like yeast, bacteria can be killed by high concentrations of alcohol and high temperatures 56

57. Example question 57

58. Mark scheme 58

59. Ethanol – Key facts Ethanol is made on an industrial scale as a fuel, a solvent and as a feedstock for other processes; There is a limit to the concentration of ethanol solution that can be made by fermentation and there are optimum conditions of pH and temperature. Ethanol solution can be concentrated by distillation to make products such as whisky and brandy; Genetically modified E. coli bacteria can be used to convert waste biomass from a range of sources into ethanol and recall the optimum conditions for the process; Ethane from crude oil can be converted into ethanol Evaluating the sustainability of each process is important. 59

60. Plants photosynthesise Remove CO 2 from atmosphere Fermentation produces ethanol fuel Burning Releases CO 2 into atmosphere Replanting Photosynthesis removes CO 2 Bioethanol cycle 60

61. Balancing carbon cycle equations 61

62. Balancing carbon cycle equations 62

63. Balancing carbon cycle equations 63

64. Carboxylic acids C7.1 64

65. What do I need to know? 1.understand that the properties of carboxylic acids are due to the presence of the –COOH functional group; 2.recall the names and formulae of methanoic and ethanoic acids; 3.recall that many carboxylic acids have unpleasant smells and tastes and are responsible for the smell of sweaty socks and the taste of rancid butter; 4.understand that carboxylic acids show the characteristic reactions of acids with metals, alkalis and carbonates; 5.recall that vinegar is a dilute solution of ethanoic acid. 65

66. Can you recognise the functional group? Circle which of these is a carboxylic acid? 66

67. Answer This is a carboxylic acid 67

68. Methanoic and Ethanoic Methanoic acidEthanoic acid (VINEGAR) 68

69. Organic or CARBOXYLIC acids are part of life itself and can be found in many animals and plants. Many acids are part of life itself, they are known as CARBOXYLIC acids Acids in nature 69

70. Reactions of carboxylic acids Reaction of carboxylic acids 1) Acid + metal  salt + hydrogen Ethanoic acid + magnesium  magnesium ethanoate + hydrogen 2) Acid + metal oxide  salt + water Ethanoic acid + copper oxide  copper ethanoate + water 3) Acid + metal carbonate  salt + water + carbon dioxide Ethanoic acid + sodium carbonate  sodium ethanoate + water + carbon dioxide 70

71. Example Question 71

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73. Example question 73

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75. Example question 75

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77. Esters, Fats and Oils C7.1 77

78. What do I need to know? 1. Recall the method for producing an ester using reflux 2. Describe how fats and oils are all types of ester and explain how margarine is made 3. Explain how bromine water can be used to test whether a fat is saturated or unsaturated. 78

79. Making esters What type of organic chemicals do you need to mix together? Can you name the ester made from ethanoic acid and methanol? 79

80. Making esters What type of organic chemicals do you need to mix together? A carboxylic acid and an alcohol with an acid catalyst Can you name the ester made from ethanoic acid and methanol? Methyl ethanoate 80

81. Esters 81

82. Example question 82

83. Mark scheme 83

84. Making esters RefluxDistillationPurificationDrying 84

85. Reflux apparatus 85

86. How do I describe reflux for an exam? 1.Mixture heated in flask (1) … 2.with condenser above (1) … 3.so no liquid is lost by evaporation and allows longer time for the reaction (1) 86

87. Distillation 87

88. Describing distillation 1.The mixture is heated 2.At the boiling point of the ester is becomes a vapour 3.The vapour is condensed in the condenser 4.The liquid is collected 88

89. Purification 1.Collected ester is shaken in a separating funnel with distilled water. 2.Impurities dissolve in the water 3.Impurities are tapped off Ester 89

90. Drying 1.Solid drying agent is added to the product 2.This could be calcium chloride or sodium sulphate 3.This removes water from the product 90

91. Example question 91

92. Mark scheme 92

93. Example question 93

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95. Example question 95

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97. Fats and oils These are a special type of ester made from glycerol and fatty acids. 97

98. Fats and oils Removal of water in the condensation reaction makes a fat or oil 98

99. Saturated or unsaturated? Have you heard these terms on the television? Vegetable oil is mostly unsaturated Animal fat is mostly saturated 99

100. Double bonds or not A saturated fat has no C=C double bonds (alkene functional groups) and is usually a solid fat like margarine or animal fat. An unsaturated fat has C=C double bonds and is usually an oil like vegetable oil. 100

101. Example question 101

102. Mark scheme 102

103. Making margarine To make margarine we have to saturate vegetable oil by bubbling hydrogen gas through the oil. This process is called hydrogenation 103

104. Is a fat or oil saturated or not? 104

105. Example question 105

106. Mark scheme 106

107. Hydrolysis When an ester is hydrolysed it goes back to an acid and alcohol We can hydrolyse by adding acid or alkali (NaOH). 107

108. Example question 108

109. Mark scheme 109

110. Energy changes in chemistry C7.2 110

111. Quiz When a chemical reaction takes place heat may be given out or taken in. 1.Can you remember the word we use when heat is given out? 2.Can you remember the word we use when heat is taken in? 111

112. What do I need to know? 1.Recall and use the terms ENDOTHERMIC and EXOTHERMIC 2.Describe examples of ENDOTHERMIC and EXOTHERMIC reactions. 3.Use simple energy level diagrams to represent ENDOTHERMIC and EXOTHERMIC reactions. 112

113. Change in energy 113

114. Definitions 114

115. Energy level diagrams Heat taken in Heat given out 115

116. Energy level diagrams EndothermicExothermic Heat taken in Heat given out Energy level of products is higher than reactants so heat taken in. Energy level of products is lower than reactants so heat given out. 116

117. Example question 117

118. Mark scheme 118

119. Bond enthalpies C7.2 119

120. Quick quiz 1.Reactions where the products are at a lower energy than the reactants are endothermic (TRUE/FALSE) 2.Activation energy is the amount of energy given out when a reaction takes place (TRUE/FALSE) 3.A reaction which is exothermic transfers heat energy to the surroundings (TRUE/FALSE) 4.How can we tell if a reaction is exothermic or endothermic? 5.Sketch the energy profile for an endothermic reaction. 6.When methane (CH 4 ) burns in oxygen (O 2 ) bonds between which atoms need to be broken? 120

121. Answers 1.Reactions where the products are at a lower energy than the reactants are endothermic (TRUE/FALSE) 2.Activation energy is the amount of energy given out when a reaction takes place (TRUE/FALSE) 3.A reaction which is exothermic transfers heat energy to the surroundings (TRUE/FALSE) 4.How can we tell if a reaction is exothermic or endothermic? 5.Sketch the energy profile for an endothermic reaction. 6.When methane (CH 4 ) burns in oxygen (O 2 ) bonds between which atoms need to be broken? FALSE TRUE Measure the temperature change C—H bonds and O=O bonds 121

122. What do I need to know? 1. Recall that energy is needed to break chemical bonds and energy is given out when chemical bonds form 2. Identify which bonds are broken and which are made when a chemical reaction takes place. 3. Use data on the energy needed to break covalent bonds to estimate the overall energy change for a reaction. 122

123. Activation energy revisited What is the activation energy of a reaction? The energy needed to start a reaction. BUT what is that energy used for and why does the reaction need it if energy is given out overall? The activation energy is used to break bonds so that the reaction can take place. 123

124. Burning methane Consider the example of burning methane gas. CH 4 + 2O 2  CO 2 + 2H 2 O This reaction is highly exothermic, it is the reaction that gives us the Bunsen flame. However mixing air (oxygen) with methane is not enough. I need to add energy (a flame). 124

125. What happens when the reaction gets the activation energy? Bond Forming Bond Breaking Progress of reaction Energy in chemicals O O O O H C H H H O O O O C H HHH O C O O O H H H H 125

126. Using bond enthalpies By using the energy that it takes to break/make a particular bond we can work out the overall enthalpy/energy change for the reaction. Sum (bonds broken) – Sum (bonds made) = Energy change 126

127. BIN MIX Breaking bonds is ENDOTHERMIC energy is TAKEN IN when bonds are broken Making bonds is EXOTHERMIC energy is GIVEN OUT when bonds are made. 127

128. Bond enthalpies BondBond enthalpy (kJ)BondBond enthalpy (kJ) C—H435Cl—Cl243 C—C348C—Cl346 H—H436H—Cl452 H—O463O=O498 C=O804 C=C614 128

129. Can you work out the energy change for this reaction? 129

130. The answer is -120 kJ 130

131. Example question part 1 131

132. Question part 2 132

133. Question part 3 133

134. Mark scheme 134

135. Challenge question The true value for the energy change is often slightly different from the value calculated using bond enthalpies. Why do you think this is? 135

136. Example question The calculated value is 120 kJ 136

137. Mark scheme 137

138. Definitions Write each of these phrases in your book with a definition in your own words: Exothermic reaction Endothermic reaction Activation energy Catalyst Bond energy/enthalpy 138

139. How did you do? Exothermic reaction A reaction which gives energy out to the surroundings. Endothermic reaction A reaction which takes in energy from the surroundings. Activation energy The energy required to start a reaction by breaking bonds in the reactants Catalyst A substance that increases the rate of a reaction by providing an alternative pathway with lower activation energy. It is not used up in the process of the reaction Bond energy/enthalpy The energy required to break a certain type of bond. The negative value is the energy given out when that bond is made. 139

140. Popular exam question 1.Explain why a reaction is either exothermic or endothermic? -------------------------------------------------------------------- 140

141. Popular exam question 1.Explain why a reaction is either exothermic or endothermic? ①In a chemical reactions some bonds are broken and some bonds are made. ②Breaking bonds takes in energy. ③Making bonds gives out energy. ④If the energy given out making bonds is higher than the energy needed to break them the reaction is exothermic. ⑤If the energy needed to break bonds is higher than the energy given out making them the reaction is endothermic. 141

142. Chemical Equilibria C7.3 Reversible Reactions & Dynamic Equilibria 142

143. What do I need to know? 1.State that some chemical reactions are reversible 2.Describe how reversible reactions reach a state of equilibrium 3.Explain this using dynamic equilibrium model. 143

144. Reversible or not reversible Until now, we were careful to say that most chemical reactions were not reversible – They could not go back to the reactants once the products are formed. 144

145. Example 145

146. Reversible Some chemical reactions, however, will go backwards and forwards depending on the conditions. CoCl 2 ·6H 2 O(s)  CoCl 2 (s) + 6H 2 O(l) pink blue 146

147. How do we write them down? This is the symbol for used for reversible reactions. CoCl 2 ·6H 2 O(s) CoCl 2 (s) + 6H 2 O(l) 147

148. What is equilibrium? 148

149. Dynamic Equilibrium. 149

150. Example question 150

151. Mark scheme 151

152. Dynamic Equilibria C7.3 Controlling equilibria 152

153. What do I need to know? 1. Recall that reversible reactions reach a state of dynamic equilibrium. 2. Describe how dynamic equilibria can be affected by adding or removing products and reactants. 3. Explain the difference between a “strong” and “weak” acid in terms of equilibria 153

154. Position of the equilibrium Equilibrium can “lie” to the left or right. This is “in favour of products” or “in favour of reactants” Meaning that once equilibrium has been reached there could be more products or more reactants in the reaction vessel. 154

155. Le Chatelier’s principle If you remove product as it is made then equilibrium will move to the right to counteract the change If you add more reactant then equilibrium will move to the right to counteract the change. In industry we recycle reactants back in and remove product as it is made to push the equilibrium in favour of more product. 155

156. Complete When a system is at__________ to make more product you can_________ product or add more __________ for example by recycling them back in. To return to reactants you ______ product or remove_________. [equilibrium, add, reactant, remove, product] 156

157. Strong and weak acids 157

158. 158

159. Mark scheme 159

160. Example question 160

161. Mark scheme 161

162. Practicing definitions Write each of these phrases in your book with a definition in your own words: Reversible reaction Dynamic equilibrium Position of equilibrium Strong acid Weak acid 162

163. How did you do? Reversible reaction A reaction that can proceed in the forward or reverse directions (represented by two arrows in an equation). Dynamic equilibrium The point where the rate of the forward reaction = rate of the reverse reaction. Position of equilibrium The point where there is no further change in the concentration of either reactants or products. The position can lie to the left (favouring reactants) or right (favouring products). Strong acid An acid that is completely dissociated in water Weak acid An acid that is only partly dissociated in water because the reaction is in dynamic equilibrium and favours the reactants (LHS). 163

164. Popular exam question 1.Ethanoic acid (CH 3 COOH) is a weak acid but hydrochloric acid is a strong acid. Use ideas about ion formation and dynamic equilibrium to explain this difference. ------------------------------------------------------------------ 164

165. Popular exam question Ethanoic acid (CH 3 COOH) is a weak acid but hydrochloric acid is a strong acid. Use ideas about ion formation and dynamic equilibrium to explain this difference. ①Hydrochloric acid ionises completely ②So hydrogen ion concentration is high ③Ethanoic acid only partly dissociates because the reaction is reversible ④Equilibrium is mainly to the left ⑤So hydrogen ion concentration is low. 165

166. Analysis C7.4 – Analytical Procedures 166

167. What do I need to know? 1. Recall the difference between qualitative and quantitative methods of analysis. 2. Describe how analysis must be carried out on a sample that represents the bulk of the material under test 3. Explain why we need standard procedures for the collection, storage and preparation of samples for analysis 167

168. Qualitative vs. Quantitative 168

169. Which sample should I test? 169

170. Chemical industry 170

171. Chromatography C7.4 – paper chromatography 171

172. Chromatography 172

173. Solvents 1.The mobile phase is the solvent – the part that moves 2. In paper chromatography it is water or ethanol 173

174. Paper/column 1.The stationary phase is the paper in paper chromatography or the column in gas chromatography. 2.In thin layer chromatography it is silica gel on a glass plate 3.The stationary phase does not move. 174

175. How does the technique work? In chromatography, substances are separated by movement of a mobile phase through a stationary phase. Each component in a mixture will prefer either the mobile phase OR the stationary phase. The component will be in dynamic equilibrium between the stationary phase and the mobile phase. 175

176. Substance A This is substance A Substance A prefers the stationary phase and doesn’t move far up the paper/column. The equilibrium lies in favour of the stationary phase. 176

177. Substance B This is substance B Substance B prefers the mobile phase and moves a long way up the paper/column The equilibrium lies in favour of the mobile phase 177

178. Using a reference In chromatography we can sometimes use a known substance to measure other substances against. This will travel a known distance compared to the solvent and is known as a standard reference. 178

179. Advantages of TLC TLC has a number of advantages over paper chromatography. It is a more uniform surface chromotograms are neater and easier to interpret Solvent can be used which is useful if a substance is insoluble in water. 179

180. Past Paper Questions 180

181. Past paper question 181

182. Mark scheme 182

183. Describing how chromatography works – exam definition stationary phase is paper and mobile phase is solvent / mobile phase moves up through stationary phase (1) for each compound there is a dynamic equilibrium between the two phases (1) how far each compound moves depends on its distribution between the two phases (1) 183

184. Using an R f value In order to be more precise we can use measurements on the TLC plate to compare the distance travelled by our substance (the solute) with the distance travelled by the solvent. The Rf value is constant for a particular compound. The distance travelled however could be different on different chromatograms. The Rf value is always less than 1. 184

185. Rf value 185

186. Example question This question relates to the chromatogram shown in the earlier question. Refer back… 186

187. Mark scheme 187

188. Example question 188

189. Mark scheme 189

190. Past paper question 190

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194. Mark scheme 194

195. Gas-liquid chromatography C7.4 GLC 195

196. What do I need to know? 1.recall in outline the procedure for separating a mixture by gas chromatography (gc); 2.understand the term retention time as applied to gc; 3.interpret print-outs from gc analyses. 196

197. Gas chromatography The mobile phase is an unreactive gas known as the carrier gas this is usually nitrogen The stationary phase is held inside a long column and is lots of pieces of inert solid coated in high bp liquid. The column is coiled in an oven The sample to be analysed is injected into the carrier gas stream at the start of the column. 197

198. GC 198

199. GC analysis Each component of the sample mixture has a different affinity for the stationary phase compared with the mobile phase Therefore each component travels through the column in a different time. Compounds favouring the mobile phase (usually more volatile) emerge first. A detector monitors the compounds coming out of the column and a recorder plots the signal as a chromatogram 199

200. GLC Chromatograph 200

201. Interpretation The time in the column is called the retention time Retention times are characteristic so can identify a compound Area under peak or relative heights can be used to work out relative amounts of substances 201

202. The key points – revise this! the mobile phase carries the sample (1) components are differently attracted to the stationary and mobile phases (1) the components that are more strongly attracted to the stationary phase move more slowly (1) the amount of each component in the stationary phase and in the mobile phase is determined by a dynamic equilibrium (1) 202

203. Past paper question 203

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207. Mark scheme 207

208. Titration C7.4 208

209. What do I need to know? 1.Calculate the concentration of a given volume of solution given the mass of solvent; 2.Calculate the mass of solute in a given volume of solution with a specified concentration; 3.Use the balanced equation and relative formula- masses to interpret the results of a titration; 209

210. Concentration We can measure the concentration of solution in grams/litre. This is the same as g/dm 3 1dm 3 = 1000cm 3 If I want to make a solution of 17 g/dm 3 how much will I dissolve in 1dm 3. 17 g If I want to make a solution of 17g/dm 3 but I only want to make 100cm 3 of it how much will I dissolve? 1.7g 210

211. Making standard solutions For a solution of 17g/dm 3 First I will measure 17g of solid on an electronic balance 211

212. Making standard solutions Now I must dissolve it in a known 1dm 3 of water. I transfer it to a volumetric flask and fill up with distilled water to about half the flask. I then swirl to dissolve Top up with a dropping pipette so that the meniscus is on the line. 212

213. How much to dissolve? Worked example: I want to make 250cm 3 of a solution of 100g/dm 3. How much solid do I transfer to my 250cm 3 volumetric flask? 213

214. How much to dissolve? Worked example: I want to make 250cm 3 of a solution of 100g/dm 3. 1. Work out the ratio of 250cm 3 to 1000cm 3 250/1000 = 0.25 2. I therefore need 0.25 of 100g in 250cm 3 which is 0.25x100=25g 214

215. General rule 215

216. Practie - how much to dissolve? I want to make 250cm 3 of a solution of 63.5g/dm 3. How much solid do I transfer to my 250cm 3 volumetric flask? 250/1000 x 63.5 = 15.9 g 216

217. Practice - how much to dissolve? I want to make 100cm 3 of a solution of 63.5g/dm 3. How much solid do I transfer to my 100cm 3 volumetric flask? 100/1000 x 63.5 = 6.35 g 217

218. Concentration from mass and volume We need to rearrange this: To give 218

219. What is the concentration of? 1.12g dissolved in 50cm 3 2.50g dissolved in 100cm 3 3.47g dissolved in 1000cm 3 4.200g dissolved in 250cm 3 219

220. What is the concentration of? 1.12g dissolved in 50cm 3 = 1000/50 x 12 = 240g/dm 3 2.50g dissolved in 100cm 3 =1000/100 x 50 = 500g/dm3 3.47g dissolved in 1000cm 3 = 1000/1000 x 47 = 47g/dm 3 4.200g dissolved in 250cm 3 1000/250 x 200 = 800g/dm 3 220

221. Solutions from stock solutions Stock solution highest concentration use to make other solutions Extract a portion of stock solution as calculated Dilute with distilled water Making a known volume of a lower concentration 221

222. Making solutions from stock solutions If I have a solution containing 63g/dm 3, how do I make up 250cm 3 of a solution of concentration 6.3g/dm 3 ? To make 1dm 3 of 6.3g/dm 3 I would need 100cm 3 To make 250cm 3 of 6.3g/dm 3 I would therefore need 25cm 3 and make it up to 250cm 3 with distilled water 222

223. Working out masses We can use the useful relationship Where Mr is the molecular mass eg Mr of NaOH is (23 + 16 + 1) = 40 This can help us to calculate an unknown mass 223

224. Titration calculations In a titration we have added a known amount of one substance usually an acid (in the burette) to a known amount of another substance usually an alkali (in the conical flask). The amount added allows us to determine the concentration of the unknown. 224

225. Titration equipment 225

226. Using a table It can be helpful to sketch a table to keep track of information you know… ValueAcidAlkali Volume (cm 3 ) Mass (g) Concentration (g/dm 3 ) Molecular weight (Mr) 226

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228. Mark scheme 228

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230. Mark scheme 230

231. Uncertainty Uncertainty is a quantification of the doubt about the measurement result. In a titration the uncertainty is the range of the results. If results are reliable then it will be within 0.2cm 3 NOTE THAT THIS IS RELIABLE NOT NECESSARILY ACCURATE 231

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233. Mark scheme 233

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235. Mark scheme 235

236. C7.5 Green Chemistry The Chemical Industry 236

237. What do I need to know? 1.Recall and use the terms 'bulk' (made on a large scale) and 'fine' (made on a small scale) in terms of the chemical industry with examples; 2.Describe how new chemical products or processes are the result of an extensive programme of research and development; 3.Explain the need for strict regulations that control chemical processes, storage and transport. 237

238. Bulk processes A bulk process manufactures large quantities of relatively simple chemicals often used as feedstocks (ingredients) for other processes. Examples include ammonia, sulfuric acid, sodium hydroxide and phosphoric acid. 40 million tonnes of H 2 SO 4 are made in the US every year. 238

239. Fine processes Fine processes manufacture smaller quantities of much more complex chemicals including pharmaceuticals, dyes and agrochemicals. Examples include drugs, food additives and fragrances 35 thousand tonnes of paracetamol are made in the US every year. 239

240. Example question 240

241. Mark scheme 241

242. Research and Development All chemicals are produced following an extensive period of research and development. Chemicals made in the laboratory need to be “scaled up” to be manufactured on the plant. 242

243. Research in the lab 243

244. Examples of making a process viable Trying to find suitable conditions – compromise between rate and equilibrium Trying to find a suitable catalyst – increases rate and cost effective as not used up in the process. 244

245. Catalysts Can you give a definition of a catalyst? A substance which speeds up the rate of a chemical reaction by providing an alternative reaction pathway. The catalyst is not used up in the process Catalysts can control the substance formed eg Ziegler Natta catalysts. 245

246. Regulation of the chemical industry Governments have strict regulations to control chemical processes Storage and transport of chemicals requires licenses and strict protocol. Why? To protect people and the environment. 246

247. Example question 247

248. Mark scheme 248

249. Process development 249

250. Example question – part 1 250

251. Example question part - 2 251

252. Mark scheme 252

253. Example question – part 3 253

254. Mark scheme 254

255. Factors affecting the sustainability of a process Sustainability renewable feedstock atom economy type of waste and disposal energy inputs and outputs environmental impact health and safety risks social and economic benefits 255

256. Example question 256

257. Mark scheme 257

258. Atom economy 258

259. Atom economy calculation For example, what is the atom economy for making hydrogen by reacting coal with steam? Write the balanced equation: C(s) + 2H 2 O(g) → CO 2 (g) + 2H 2 (g) Write out the Mr values underneath: C(s) + 2H 2 O(g) → CO 2 (g) + 2H 2 (g) 12 2 × 18 44 2 × 2 Total mass of reactants 12 + 36 = 48g Mass of desired product (H 2 ) = 4g % atom economy = 4⁄48 × 100 = 8.3% 259

260. Example question 260

261. Example question – part 2 261

262. Mark scheme 262