JK-TK/Newdata huggingface dataset:
Hydrolysis/Hydration is the reaction of a compound/substance with water. Alkenes react with water vapour/steam at high temperatures and high pressures in presence of phosphoric acid catalyst to form alkanols.i.e. Alkenes + Water - H3PO4 catalyst-> Alkanol Examples (i)Ethene is mixed with steam over a phosphoric acid catalyst at 300oC temperature and 60 atmosphere pressure to form ethanol Ethene + water ---60 atm/300oC/ H3PO4 --> Ethanol H2C =CH2 (g) + H2O(l) --60 atm/300oC/ H3PO4 --> CH3 CH2OH(l) This is the main method of producing large quantities of ethanol instead of fermentation (ii) Propene + water ---60 atm/300oC/ H3PO4 --> Propanol CH3C =CH2 (g) + H2O(l) --60 atm/300oC/ H3PO4 --> CH3 CH2 CH2OH(l) (iii) Butene + water ---60 atm/300oC/ H3PO4 --> Butanol CH3 CH2 C=CH2 (g) + H2O(l) --60 atm/300oC/ H3PO4 --> CH3 CH2 CH2 CH2OH(l) II. Dehydration is the process which concentrated sulphuric(VI)acid (dehydrating agent) removes water from a compound/substances. Concentrated sulphuric(VI)acid dehydrates alkanols to the corresponding alkenes at about 180oC. i.e Alkanol --Conc. H2 SO4/180oC--> Alkene + Water Examples
75 1. At 180oC and in presence of Concentrated sulphuric(VI)acid, ethanol undergoes dehydration to form ethene. Ethanol ---180oC/ H2SO4 --> Ethene + Water CH3 CH2OH(l) --180oC/ H2SO4 --> H2C =CH2 (g) + H2O(l) 2. Propanol undergoes dehydration to form propene.
At 180oC and in presence of Concentrated sulphuric(VI)acid, ethanol undergoes dehydration to form ethene. Ethanol ---180oC/ H2SO4 --> Ethene + Water CH3 CH2OH(l) --180oC/ H2SO4 --> H2C =CH2 (g) + H2O(l) 2. Propanol undergoes dehydration to form propene. Propanol ---180oC/ H2SO4 --> Propene + Water CH3 CH2 CH2OH(l) --180oC/ H2SO4 --> CH3CH =CH2 (g) + H2O(l) 3. Butanol undergoes dehydration to form Butene. Butanol ---180oC/ H2SO4 --> Butene + Water CH3 CH2 CH2CH2OH(l) --180oC/ H2SO4 --> CH3 CH2C =CH2 (g) + H2O(l) 3. Pentanol undergoes dehydration to form Pentene. Pentanol ---180oC/ H2SO4 --> Pentene + Water CH3 CH2 CH2 CH2 CH2OH(l)--180oC/ H2SO4-->CH3 CH2 CH2C =CH2 (g)+H2O(l) (l)Similarities of alkanols with Hydrocarbons I. Similarity with alkanes Both alkanols and alkanes burn with a blue non-sooty flame to form carbon(IV)oxide(in excess air/oxygen)/carbon(II)oxide(in limited air) and water. This shows they are saturated with high C:H ratio. e.g. Both ethanol and ethane ignite and burns in air with a blue non-sooty flame to form carbon(IV)oxide(in excess air/oxygen)/carbon(II)oxide(in limited air) and water.
This shows they are saturated with high C:H ratio. e.g. Both ethanol and ethane ignite and burns in air with a blue non-sooty flame to form carbon(IV)oxide(in excess air/oxygen)/carbon(II)oxide(in limited air) and water. CH2 CH2OH(l) + 3O2(g) -Excess air-> 2CO2 (g) + 3H2 O(l) CH2 CH2OH(l) + 2O2(g) -Limited air-> 2CO (g) + 3H2 O(l) CH3 CH3(g) + 3O2(g) -Excess air-> 2CO2 (g) + 3H2 O(l) 2CH3 CH3(g) + 5O2(g) -Limited air-> 4CO (g) + 6H2 O(l) II. Similarity with alkenes/alkynes Both alkanols(R-OH) and alkenes/alkynes(with = C = C = double and – C = C- triple ) bond: (i)decolorize acidified KMnO4 (ii)turns Orange acidified K2Cr2O7 to green. Alkanols(R-OH) are oxidized to alkanals(R-O) ant then alkanoic acids(R-OOH). Alkenes are oxidized to alkanols with duo/double functional groups. Examples 1.When ethanol is warmed with three drops of acidified K2Cr2O7 the orange of acidified K2Cr2O7 turns to green. Ethanol is oxidized to ethanol and then to ethanoic acid. 76 Ethanol + [O] -> Ethanal + [O] -> Ethanoic acid CH3CH2OH + [O] -> CH3CH2O + [O] -> CH3COOH 2.When ethene is bubbled in a test tube containing acidified K2Cr2O7 ,the orange of acidified K2Cr2O7 turns to green. Ethene is oxidized to ethan-1,2-diol. Ethene + [O] -> Ethan-1,2-diol. H2C=CH2 + [O] -> HOCH2 -CH2OH III. Differences with alkenes/alkynes Alkanols do not decolorize bromine and chlorine water.
Ethene + [O] -> Ethan-1,2-diol. H2C=CH2 + [O] -> HOCH2 -CH2OH III. Differences with alkenes/alkynes Alkanols do not decolorize bromine and chlorine water. Alkenes decolorizes bromine and chlorine water to form halogenoalkanols Example When ethene is bubbled in a test tube containing bromine water,the bromine water is decolorized. Ethene is oxidized to bromoethanol. Ethene + Bromine water -> Bromoethanol. H2C=CH2 + HOBr -> BrCH2 -CH2OH IV. Differences in melting and boiling point with Hydrocarbons Alkanos have higher melting point than the corresponding hydrocarbon (alkane/alkene/alkyne) This is because most alkanols exist as dimer.A dimer is a molecule made up of two other molecules joined usually by van-der-waals forces/hydrogen bond or dative bonding. Two alkanol molecules form a dimer joined by hydrogen bonding. Example In Ethanol the oxygen atom attracts/pulls the shared electrons in the covalent bond more to itself than Hydrogen. This creates a partial negative charge (δ-) on oxygen and partial positive charge(δ+) on hydrogen. Two ethanol molecules attract each other at the partial charges through Hydrogen bonding forming a dimmer. H H H H C C O H H H H H O C C H Hydrogen bonds Covalent bonds
77 H H Dimerization of alkanols means more energy is needed to break/weaken the Hydrogen bonds before breaking/weakening the intermolecular forces joining the molecules of all organic compounds during boiling/melting. E.USES OF SOME ALKANOLS (a)Methanol is used as industrial alcohol and making methylated spirit (b)Ethanol is used: 1. as alcohol in alcoholic drinks e.g Beer, wines and spirits. 2.as antiseptic to wash woulds 3.in manufacture of vanishes, ink ,glue and paint because it is volatile and thus easily evaporate 4.as a fuel when blended with petrol to make gasohol. B.ALKANOIC ACIDS (Carboxylic acids) (A) INTRODUCTION.
as alcohol in alcoholic drinks e.g Beer, wines and spirits. 2.as antiseptic to wash woulds 3.in manufacture of vanishes, ink ,glue and paint because it is volatile and thus easily evaporate 4.as a fuel when blended with petrol to make gasohol. B.ALKANOIC ACIDS (Carboxylic acids) (A) INTRODUCTION. Alkanoic acids belong to a homologous series of organic compounds with a general formula CnH2n +1 COOH and thus -COOH as the functional group .The 1st ten alkanoic acids include:
78 Alkanoic acids like alkanols /alkanes/alkenes/alkynes form a homologous series where: (i)the general name of an alkanoic acids is derived from the alkane name then ending with “–oic” acid as the table above shows. (ii) the members have R-COOH/R C-O-H as the functional group.
B.ALKANOIC ACIDS (Carboxylic acids) (A) INTRODUCTION. Alkanoic acids belong to a homologous series of organic compounds with a general formula CnH2n +1 COOH and thus -COOH as the functional group .The 1st ten alkanoic acids include:
78 Alkanoic acids like alkanols /alkanes/alkenes/alkynes form a homologous series where: (i)the general name of an alkanoic acids is derived from the alkane name then ending with “–oic” acid as the table above shows. (ii) the members have R-COOH/R C-O-H as the functional group. n General /molecular formular Structural formula IUPAC name 0 HCOOH H – C –O - H │ O Methanoic acid 1 CH3 COOH H H – C – C – O - H │ H O Ethanoic acid 2 CH3 CH2 COOH C2 H5 COOH H H H-C – C – C – O – H H H O Propanoic acid 3 CH3 CH2 CH2 COOH C3 H7 COOH H H H H- C - C – C – C – O – H H H H O Butanoic acid 4 CH3CH2CH2CH2 COOH C4 H9 COOH H H H H H - C – C - C – C – C – O – H H H H H O Pentanoic acid 5 CH3CH2 CH2CH2CH2 COOH C5 H11 COOH H H H H H H C - C – C - C – C – C – O – H H H H H H O Hexanoic acid 6 CH3CH2 CH2 CH2CH2CH2 COOH C6 H13 COOH H H H H H H H C C - C – C - C – C – C – O – H H H H H H H O Pentanoic acid
79 O (iii)they have the same general formula represented by R-COOH where R is an alkyl group. (iv)each member differ by –CH2- group from the next/previous. (v)they show a similar and gradual change in their physical properties e.g. boiling and melting point. (vi)they show similar and gradual change in their chemical properties.
(v)they show a similar and gradual change in their physical properties e.g. boiling and melting point. (vi)they show similar and gradual change in their chemical properties. (vii) since they are acids they show similar properties with mineral acids. (B) ISOMERS OF ALKANOIC ACIDS. Alkanoic acids exhibit both structural and position isomerism. The isomers are named by using the following basic guidelines (i)Like alkanes. identify the longest carbon chain to be the parent name. (ii)Identify the position of the -C-O-H functional group to give it the smallest O /lowest position. (iii)Identify the type and position of the side group branches. Practice examples on isomers of alkanoic acids 1.Isomers of butanoic acid C3H7COOH CH3 CH2 CH2 COOH Butan-1-oic acid CH3 H2C C COOH 2-methylpropan-1-oic acid 2-methylpropan-1-oic acid and Butan-1-oic acid are structural isomers because the position of the functional group does not change but the arrangement of the atoms in the molecule does. 2.Isomers of pentanoic acid C4H9COOH CH3CH2CH2CH2 COOH pentan-1-oic acid CH3 CH3CH2CH COOH 2-methylbutan-1-oic acid
80 CH3 H3C C COOH 2,2-dimethylpropan-1-oic acid CH3 3.Ethan-1,2-dioic acid O O HOOC- COOH // H - O – C - C – O – H 4.Propan-1,3-dioic acid O H O HOOC- CH2COOH // H - O – C – C - C – O – H H 5.Butan-1,4-dioic acid O H H O HOOC CH2 CH2 COOH H- O – C – C - C – C –O – H H H 6.2,2-dichloroethan-1,2-dioic acid HOOCCHCl2 Cl H – O - C – C – Cl O H (C) LABORATORY AND INDUSTRIAL PREPARATIONOF ALKANOIC ACIDS.
(iii)Identify the type and position of the side group branches. Practice examples on isomers of alkanoic acids 1.Isomers of butanoic acid C3H7COOH CH3 CH2 CH2 COOH Butan-1-oic acid CH3 H2C C COOH 2-methylpropan-1-oic acid 2-methylpropan-1-oic acid and Butan-1-oic acid are structural isomers because the position of the functional group does not change but the arrangement of the atoms in the molecule does. 2.Isomers of pentanoic acid C4H9COOH CH3CH2CH2CH2 COOH pentan-1-oic acid CH3 CH3CH2CH COOH 2-methylbutan-1-oic acid
80 CH3 H3C C COOH 2,2-dimethylpropan-1-oic acid CH3 3.Ethan-1,2-dioic acid O O HOOC- COOH // H - O – C - C – O – H 4.Propan-1,3-dioic acid O H O HOOC- CH2COOH // H - O – C – C - C – O – H H 5.Butan-1,4-dioic acid O H H O HOOC CH2 CH2 COOH H- O – C – C - C – C –O – H H H 6.2,2-dichloroethan-1,2-dioic acid HOOCCHCl2 Cl H – O - C – C – Cl O H (C) LABORATORY AND INDUSTRIAL PREPARATIONOF ALKANOIC ACIDS. In a school laboratory, alkanoic acids can be prepared by adding an oxidizing agent (H+/KMnO4 or H+/K2Cr2O7)to the corresponding alkanol then warming. 81 The oxidation converts the alkanol first to an alkanal the alkanoic acid.
2.Isomers of pentanoic acid C4H9COOH CH3CH2CH2CH2 COOH pentan-1-oic acid CH3 CH3CH2CH COOH 2-methylbutan-1-oic acid
80 CH3 H3C C COOH 2,2-dimethylpropan-1-oic acid CH3 3.Ethan-1,2-dioic acid O O HOOC- COOH // H - O – C - C – O – H 4.Propan-1,3-dioic acid O H O HOOC- CH2COOH // H - O – C – C - C – O – H H 5.Butan-1,4-dioic acid O H H O HOOC CH2 CH2 COOH H- O – C – C - C – C –O – H H H 6.2,2-dichloroethan-1,2-dioic acid HOOCCHCl2 Cl H – O - C – C – Cl O H (C) LABORATORY AND INDUSTRIAL PREPARATIONOF ALKANOIC ACIDS. In a school laboratory, alkanoic acids can be prepared by adding an oxidizing agent (H+/KMnO4 or H+/K2Cr2O7)to the corresponding alkanol then warming. 81 The oxidation converts the alkanol first to an alkanal the alkanoic acid. NB Acidified KMnO4 is a stronger oxidizing agent than acidified K2Cr2O7 General equation: R- CH2 – OH + [O] --H+/KMnO4--> R- CH –O + H2O(l) (alkanol) (alkanal) R- CH – O + [O] --H+/KMnO4--> R- C –OOH (alkanal) (alkanoic acid) Examples 1.Ethanol on warming in acidified KMnO4 is oxidized to ethanal then ethanoic acid .
In a school laboratory, alkanoic acids can be prepared by adding an oxidizing agent (H+/KMnO4 or H+/K2Cr2O7)to the corresponding alkanol then warming. 81 The oxidation converts the alkanol first to an alkanal the alkanoic acid. NB Acidified KMnO4 is a stronger oxidizing agent than acidified K2Cr2O7 General equation: R- CH2 – OH + [O] --H+/KMnO4--> R- CH –O + H2O(l) (alkanol) (alkanal) R- CH – O + [O] --H+/KMnO4--> R- C –OOH (alkanal) (alkanoic acid) Examples 1.Ethanol on warming in acidified KMnO4 is oxidized to ethanal then ethanoic acid . CH3- CH2 – OH + [O] --H+/KMnO4--> CH3- CH –O + H2O(l) (ethanol) (ethanal) CH3- CH – O + [O] --H+/KMnO4--> CH3- C –OOH (ethanal) (ethanoic acid) 2Propanol on warming in acidified KMnO4 is oxidized to propanal then propanoic acid CH3- CH2 CH2 – OH + [O] --H+/KMnO4--> CH3- CH2 CH –O + H2O(l) (propanol) (propanal) CH3- CH – O + [O] --H+/KMnO4--> CH3- C –OOH (propanal) (propanoic acid) Industrially,large scale manufacture of alkanoic acid like ethanoic acid is obtained from: (a)Alkenes reacting with steam at high temperatures and pressure in presence of phosphoric(V)acid catalyst and undergo hydrolysis to form alkanols. i.e. Alkenes + Steam/water -- H2PO4 Catalyst--> Alkanol The alkanol is then oxidized by air at 5 atmosphere pressure with Manganese (II)sulphate(VI) catalyst to form the alkanoic acid.
CH3- CH2 – OH + [O] --H+/KMnO4--> CH3- CH –O + H2O(l) (ethanol) (ethanal) CH3- CH – O + [O] --H+/KMnO4--> CH3- C –OOH (ethanal) (ethanoic acid) 2Propanol on warming in acidified KMnO4 is oxidized to propanal then propanoic acid CH3- CH2 CH2 – OH + [O] --H+/KMnO4--> CH3- CH2 CH –O + H2O(l) (propanol) (propanal) CH3- CH – O + [O] --H+/KMnO4--> CH3- C –OOH (propanal) (propanoic acid) Industrially,large scale manufacture of alkanoic acid like ethanoic acid is obtained from: (a)Alkenes reacting with steam at high temperatures and pressure in presence of phosphoric(V)acid catalyst and undergo hydrolysis to form alkanols. i.e. Alkenes + Steam/water -- H2PO4 Catalyst--> Alkanol The alkanol is then oxidized by air at 5 atmosphere pressure with Manganese (II)sulphate(VI) catalyst to form the alkanoic acid. Alkanol + Air -- MnSO4 Catalyst/5 atm pressure--> Alkanoic acid Example Ethene is mixed with steam over a phosphoric(V)acid catalyst,300oC temperature and 60 atmosphere pressure to form ethanol. 82 CH2=CH2 + H2O -> CH3 CH2OH (Ethene) (Ethanol) This is the industrial large scale method of manufacturing ethanol Ethanol is then oxidized by air at 5 atmosphere pressure with Manganese (II)sulphate(VI) catalyst to form the ethanoic acid. CH3 CH2OH + [O] -- MnSO4 Catalyst/5 atm pressure--> CH3 COOH (Ethanol) (Ethanoic acid) (b)Alkynes react with liquid water at high temperatures and pressure in presence of Mercury(II)sulphate(VI)catalyst and 30% concentrated sulphuric(VI)acid to form alkanals.
Alkanol + Air -- MnSO4 Catalyst/5 atm pressure--> Alkanoic acid Example Ethene is mixed with steam over a phosphoric(V)acid catalyst,300oC temperature and 60 atmosphere pressure to form ethanol. 82 CH2=CH2 + H2O -> CH3 CH2OH (Ethene) (Ethanol) This is the industrial large scale method of manufacturing ethanol Ethanol is then oxidized by air at 5 atmosphere pressure with Manganese (II)sulphate(VI) catalyst to form the ethanoic acid. CH3 CH2OH + [O] -- MnSO4 Catalyst/5 atm pressure--> CH3 COOH (Ethanol) (Ethanoic acid) (b)Alkynes react with liquid water at high temperatures and pressure in presence of Mercury(II)sulphate(VI)catalyst and 30% concentrated sulphuric(VI)acid to form alkanals. Alkyne + Water -- Mercury(II)sulphate(VI)catalyst--> Alkanal The alkanal is then oxidized by air at 5 atmosphere pressure with Manganese (II) sulphate(VI) catalyst to form the alkanoic acid. Alkanal + air/oxygen -- Manganese(II)sulphate(VI)catalyst--> Alkanoic acid Example Ethyne react with liquid water at high temperature and pressure with Mercury (II) sulphate (VI)catalyst and 30% concentrated sulphuric(VI)acid to form ethanal. CH = CH + H2O --HgSO4--> CH3 CH2O (Ethyne) (Ethanal) This is another industrial large scale method of manufacturing ethanol from large quantities of ethyne found in natural gas. Ethanal is then oxidized by air at 5 atmosphere pressure with Manganese (II)sulphate(VI) catalyst to form the ethanoic acid. CH3 CH2O + [O] -- MnSO4 Catalyst/5 atm pressure--> CH3 COOH (Ethanal) (Oxygen from air) (Ethanoic acid) (D) PHYSICAL AND CHEMICAL PROPERTIES OF ALKANOIC ACIDS.
CH = CH + H2O --HgSO4--> CH3 CH2O (Ethyne) (Ethanal) This is another industrial large scale method of manufacturing ethanol from large quantities of ethyne found in natural gas. Ethanal is then oxidized by air at 5 atmosphere pressure with Manganese (II)sulphate(VI) catalyst to form the ethanoic acid. CH3 CH2O + [O] -- MnSO4 Catalyst/5 atm pressure--> CH3 COOH (Ethanal) (Oxygen from air) (Ethanoic acid) (D) PHYSICAL AND CHEMICAL PROPERTIES OF ALKANOIC ACIDS. I.Physical properties of alkanoic acids
83 The table below shows some physical properties of alkanoic acids Alkanol Melting point(oC) Boiling point(oC) Density(gcm-3) Solubility in water Methanoic acid 18.4 101 1.22 soluble Ethanoic acid 16.6 118 1.05 soluble Propanoic acid -2.8 141 0.992 soluble Butanoic acid -8.0 164 0.964 soluble Pentanoic acid -9.0 187 0.939 Slightly soluble Hexanoic acid -11 205 0.927 Slightly soluble Heptanoic acid -3 223 0.920 Slightly soluble Octanoic acid 11 239 0.910 Slightly soluble Nonanoic acid 16 253 0.907 Slightly soluble Decanoic acid 31 269 0.905 Slightly soluble From the table note the following: (i) Melting and boiling point decrease as the carbon chain increases due to increase in intermolecular forces of attraction between the molecules requiring more energy to separate the molecules. (ii) The density decreases as the carbon chain increases as the intermolecular forces of attraction increases between the molecules making the molecule very close reducing their volume in unit mass. (iii) Solubility decreases as the carbon chain increases as the soluble –COOH end is shielded by increasing insoluble alkyl/hydrocarbon chain. (iv) Like alkanols ,alkanoic acids exist as dimmers due to the hydrogen bonds within the molecule. i.e..
(iii) Solubility decreases as the carbon chain increases as the soluble –COOH end is shielded by increasing insoluble alkyl/hydrocarbon chain. (iv) Like alkanols ,alkanoic acids exist as dimmers due to the hydrogen bonds within the molecule. i.e.. 84 jgthungu@gmail.com104Hydrogen bondscovalent bondsR1C O δ-…….….…H δ+O δO δH δ+……..….O δCR2R1 and 2 are extensions of the molecule.For ethanoic acid the extension is made up of CH3 – to make the structure; jgthungu@gmail.com105For ethanoic acid the extension is made up of CH3 – to make the structure;Hydrogen bondscovalent bonds CH3CO δ-…………… H δ+O δO δH δ+…………O δCCH3Ethanoic acid has a higher melting/boiling point than ethanol .This is because ethanoic acid has two/more hydrogen bond than ethanol. II Chemical properties of alkanoic acids The following experiments shows the main chemical properties of ethanoic (alkanoic) acid. (a)Effect on litmus papers Experiment Dip both blue and red litmus papers in ethanoic acid. Repeat with a solution of succinic acid, citric acid, oxalic acid, tartaric acid and dilute nitric(V)acid. Sample observations Solution/acid Observations/effect on litmus papers Inference Ethanoic acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion
85 Succinic acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Citric acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Oxalic acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Tartaric acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Nitric(V)acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Explanation All acidic solutions contains H+/H3O+(aq) ions.
(a)Effect on litmus papers Experiment Dip both blue and red litmus papers in ethanoic acid. Repeat with a solution of succinic acid, citric acid, oxalic acid, tartaric acid and dilute nitric(V)acid. Sample observations Solution/acid Observations/effect on litmus papers Inference Ethanoic acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion
85 Succinic acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Citric acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Oxalic acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Tartaric acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Nitric(V)acid Blue litmus paper turn red Red litmus paper remain red H3O+/H+(aq)ion Explanation All acidic solutions contains H+/H3O+(aq) ions. The H+ /H3O+ (aq) ions is responsible for turning blue litmus paper/solution to red (b)pH Experiment Place 2cm3 of ethaoic acid in a test tube. Add 2 drops of universal indicator solution and determine its pH. Repeat with a solution of succinic acid, citric acid, oxalic acid, tartaric acid and dilute sulphuric (VI)acid. Sample observations Solution/acid pH Inference Ethanoic acid 4/5/6 Weakly acidic Succinic acid 4/5/6 Weakly acidic Citric acid 4/5/6 Weakly acidic Oxalic acid 4/5/6 Weakly acidic Tartaric acid 4/5/6 Weakly acidic Sulphuric(VI)acid 1/2/3 Strongly acidic Explanations Alkanoic acids are weak acids that partially/partly dissociate to release few H+ ions in solution. The pH of their solution is thus 4/5/6 showing they form weakly acidic solutions when dissolved in water.
Repeat with a solution of succinic acid, citric acid, oxalic acid, tartaric acid and dilute sulphuric (VI)acid. Sample observations Solution/acid pH Inference Ethanoic acid 4/5/6 Weakly acidic Succinic acid 4/5/6 Weakly acidic Citric acid 4/5/6 Weakly acidic Oxalic acid 4/5/6 Weakly acidic Tartaric acid 4/5/6 Weakly acidic Sulphuric(VI)acid 1/2/3 Strongly acidic Explanations Alkanoic acids are weak acids that partially/partly dissociate to release few H+ ions in solution. The pH of their solution is thus 4/5/6 showing they form weakly acidic solutions when dissolved in water. All alkanoic acid dissociate to releases the “H” at the functional group in -COOH to form the alkanoate ion; –COO- Mineral acids(Sulphuric(VI)acid, Nitric(V)acid and Hydrochloric acid) are strong acids that wholly/fully dissociate to release many H+ ions in solution. The pH of their solution is thus 1/2/3 showing they form strongly acidic solutions when dissolved in water.i.e Examples 1. CH3COOH(aq) CH3COO-(aq) + H+(aq)
86 (ethanoic acid) (ethanoate ion) (few H+ ion) 2. CH3 CH2COOH(aq) CH3 CH2COO-(aq) + H+(aq) (propanoic acid) (propanoate ion) (few H+ ion) 3. CH3 CH2 CH2COOH(aq) CH3 CH2 CH2COO-(aq) + H+(aq) (Butanoic acid) (butanoate ion) (few H+ ion) 4. HOOH(aq) HOO-(aq) + H+(aq) (methanoic acid) (methanoate ion) (few H+ ion) 5. H2 SO4 (aq) SO42- (aq) + 2H+(aq) (sulphuric(VI) acid) (sulphate(VI) ion) (many H+ ion) 6.
Put about 1cm length of polished magnesium ribbon. Test any gas produced using a burning splint. Repeat with a solution of succinic acid, citric acid, oxalic acid, tartaric acid and dilute sulphuric (VI) acid. Sample observations Solution/acid Observations Inference Ethanoic acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that burn with “pop” sound/explosion H3O+/H+(aq)ion Succinic acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that burn with “pop” sound/explosion H3O+/H+(aq)ion Citric acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that burn with “pop” sound/explosion H3O+/H+(aq)ion Oxalic acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that burn with “pop” sound/explosion H3O+/H+(aq)ion Tartaric acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that burn with “pop” sound/explosion H3O+/H+(aq)ion
87 Nitric(V)acid (i)effervescence, fizzing, bubbles (ii)colourless gas produced that burn with “pop” sound/explosion H3O+/H+(aq)ion Explanation Metals higher in the reactivity series displace the hydrogen in all acids to evolve/produce hydrogen gas and form a salt. Alkanoic acids react with metals with metals to form alkanoates salt and produce/evolve hydrogen gas .Hydrogen extinguishes a burning splint with a pop sound/explosion. Only the “H”in the functional group -COOH is /are displaced and not in the alkyl hydrocarbon chain. Alkanoic acid + Metal -> Alkanoate + Hydrogen gas. i.e. Examples 1.