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What is ionisation
The dissociation of molecules or compounds into smaller charged particles called ions
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What is the Bronsted-Lowry Theory of acids
- -An acid is a proton donor
- -A base is a proton acceptor
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Describe the ionisation of acids in water
- Acids ionise in water to release hydrogen ions
- - Acid molecules react with water by donation a proton to form a hydronium ion (H3O+)
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Identify Acetic acid
(Ethanoic acid)
- -CH3COOH
- - Used in vinegar (around 4% of vinegar is acetic acid)
-Manufactured industrially
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Identify Citric acid
(2-hydroxypropane-1,2,3-tricarboxylic acid)
- C6H8O7
- Occurs naturally in fruit
- Added to food as preservative and flavouring
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Identify Hydrochloric acid
(HCl)
- Found in the stomach of humans
-Produced industrailly on a large scale
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Identify Sulfuric acid
(H2SO4)
- Can be produced from volcanic eruptions
-Can be produced from smelting of ores
- Used as an acid catalyst
-Used as a dehydrating agent
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Describe the use of the pH scale in comparing acids and bases
- Allows us to measure acidity of various samples by comparing concentrations of H+ and OH- ions in solution
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Describe acids and their solutions with the appropriate use of the terms strong, weak, concentrated and dilute
- "Concentrated" and "Dilute" refer to the amount of acid added relative to volume of water
-"Strong" and "Weak" refer to the extent to which an acid dissociates into its ions in solution in water
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Identify pH as -Log10[H+] and explain that a change in pH of 1 means a ten-fold change in [H+]
-A formula is used to determine pH given the concentration of hydronium ions:
pH= -log[H+]
- A change in pH of 1 means a ten-fold change in [H+]
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Compare the relative strengths of equal concentrations of citric, acetic and hydrochloric acids and explain in terms of the degree of ionisation of their molecules
-HCl is a strong acid and completely ionises in solution
-Citric acid is a weak acid and only partially ionises in solution
- Acetic acid is an even weaker acid and is monoprotic
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Describe the difference between a strong and a weak acid in terms of an equilibrium between the intact molecule and its ions
Strong acids
- -Strong acids completely ionise in water to produce hydronium ions in solution
- -No equilibrium
- -e.g.

Weak Acids
- -Weak acids only partially ionise in water
- -Equilibrium is established between acid molecules and its ions
-e.g.
Strong Bases
-Strong bases completely ionise in warter to produce hydroxide ions in solution
- -e.g.

Weak Bases
- Some molecules or ions react with water to form hydroxide ions in aq solution
- -e.g.

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Explain the use of acids as food additives
- - Improves taste
- - Preserves food
-Common acids added: acetic, citric, phosphoric, propanoic
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Outline Lavoisier's theory of acids
Proposed that acids were substances that contained oxygen
- Limitations
- -Some acids contained no oxygen e.g. HCl
- -Metal oxides formed bases in solution
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Outline Davy's theory of acids
Proposed that acids were substances that contained replacable hydrogen
- Limitations
- -Could not explain why some hydrogen containing substances were not acidic
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Outline Arrhenius's theory of acids
Proposed acids were substances that ionized in solution to produce hydrogen ions
- Limitations
- - Only applied to aqueous solutions
- - Does not explain why some salts act as acids
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Identify conjugate acid/base pairs
-Products of acid-base reactions are the conjugate acids and bases
-When an acid donates a proton, it forms its conjugate base
-When a base accepts a proton, it forms its conjugate acid
- Generalisation
- -Strong acids will have weak conj bases
- -Strong bases will have weak conj acids
- -Weak acids will have stronger conj bases
- -Weak bases will have stronger conj acids
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Identify a range of salts which form acidic, basic or neutral solutions and explain their acidic, neutral or basic nature
-Neutral salts contain ions that do not react with water
-Basic salts contain ions that react with water to from OH - ions
- Acidic salts contain ions that react with water to form H 3O +ions
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Identify amphiprotic substances and construct equations to describe their behaviour in acidic and basic solutions
-Amphiprotic substances can accept or donate protons
-This means they can act as either an acid or a base
- An amphoprotic substance must contain a donateable hydrogen ion
-All amphiportic substances are amphoteric but not all amphoteric substances are amphiprotic
E.g. Water
- Acting as an acid

- Acting as a base

Self ionisation of water
-One molecule of water acts as an acid and one molecule of water acts as a base
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Identify neutralisation as a proton transfer reaction which is exothermic
-Neutralisation reactions are acid-base reactions involving a proton transfer which is exothermic
-It is exothermic since it forms covalent bonds between hydrogen and oxygen when water is formed
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Qualitatively describe the effect of buffers with reference to a specific example in a natural system
Effect of Buffers
-Buffer solutions resist changes to pH when small amounts of acids or bases are added
-Buffers are an aq mixture in roughly equal amoujnts of a weak acid and its conjugate base or a weak base and its conjugate acid
Buffers in a natural system
-The buffer system used in blood is carbonic acid and hydrogen carbonate ions
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Describe the differences between the alkanol and alkanoic acid functional groups in carbon compounds
-Alkanols have at least one hydroxly (-OH) group bonded to a carbon
-Alkanoic (carboxylic) acids have at least one carboxyl group (-COOH)
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Identify the IUPAC nomenclature for describing the esters produced by reactions of straight-chained alkanoic acids from C1 to C8 and straight-chained primary alkanols from C1 to C8
Esters are named in 2 parts
- First Part
- - Comes from alkanol
- -e.g. ethyl (suffix '-anol' changes to '-yl')
- Second Part
- - Comes from acid
- -e.g. Butanoate (suffix '-oic' acid changes to 'oate')
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What is an ester
A reaction between an alkanol and an alkanoic acid forms an organic compound called an ester
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Explain the difference in melting point and boiling point caused by straight-chained alkanoic acid and straight-chained primary alkanol structures
In Alkanols
- -C-O and O-H bonds are polar
- - Able to form hydrogen bonds: strong intermolecular forces between alkanol molecules
-Thus higher b.p. than corresponding alkanes/enes
In Alkanoic Acid
- -Additional C=O bond
- -forms even stronger hydrogen bonds: even stronger intermolecular forces
-Even more energy needed to separate molecules
Both, alkanols and alkanoic acids have higher m.ps than hydrocarbons of similar molecular mass
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Identify esterification as the reaction between an acid and an alkanol and describe, using equations, examples of esterification
-Esterification is the condensation reaction between an alkanoic acid and an alkanol to form an ester
-Esterification is reversible
- e.g.
 - conc.H2SO4 as catalyst
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Describe the purpose of using acid in esterification for catalysis
-Conc. H2SO4 is needed to lower activation energy
- Conc. H2SO4 increases yield, as it is a dehydrating agent therefore shifts the equilibrium to the right according to Le Chat
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Explain the need for refluxing during esterification
Refluxing is the process of ehating a reaction mixture in a vessel with a cooling condenser attached
- Cooling condenser prevents loss of any volatile reactant or product
-Esterification requires thermal energy to reach equilibrium , therefore, without refluxing it would take days to reach equilibrium
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Outline some examples of the occurrence, production and uses of esters
Esters are frequently found in many parts of nature
Esters have pleasant, sweet, fruity odours
Occurence
-Many odours and scents of fruits and flowers are caused by the presence of esters
-Solid animal fats and plant oils are esters
Production
-There is a substantial industry that manufactures and develops synthetic flavours and perfumes
Uses
- -Food: margarine, flavours, fragrances
- -Soaps
- -Solvents
- -Cosmetics
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Identify and describe the uses of esters as flavours and perfumes in processed foods and cosmetics
-Esters are widely used as flavours and perfumes in processed foods and cosmetics
- Ethyl Ethanoate
- -has a pear and wine-like odour
- -used in nail polish remover and perfumes
- Butyl Ethanoate
- -Pleasant odour
- -used in flavouring of confectionary and ice cream
- -alse used as solvent
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