Chemistry 5.3 Flashcards by Georgie Howard

What is the functional group of alcohols?

-OH

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What are the 3 ways ethanol can undergo oxidation?

Combustion
Microbial oxidation
Heating with potassium dichromate (oxidising agent)/ chemical oxidation

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What is the word equation for the combustion of ethanol?

ethanol + oxygen –> carbon dioxide + water

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Describe combustion of ethanol

Ethanol combusts completely due to oxygen atom in -OH group.
Non-luminous, blue flame observed

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Describe microbial oxidation

Bacteria uses oxygen in the air to oxidise ethanol into ethanoic acid

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What can microbial oxidation only occur in the prescence of?

Can only happen aerobically, only if bacteria is in prescence of oxygen

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What is vinegar?

An aqueous solution of ethanoic acid (formed during microbial oxidation of ethanol)

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What is the word equation for microbial oxidation of ethanol?

Ethanol + oxygen –> ethanoic acid + water

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What is ethanol heated with when being oxidised by an oxidising agent (chemical oxidation)?

Potassium dichromate (VI) solution in sulfuric acid

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What is produced when ethanol undergoes oxidation due to an oxidising agent?

ethanoic acid + water

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Chemical equation for oxidation of ethanol with potassium (IV) dichromate

CH3CH2OH + [O] –> CH3COOH +H2O

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What is the colour change observed when ethanol is oxidised to produce ethanoic acid (using potassium dichromate and sulphuric acid)?

Orange to green

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What is the reason for the colour change during chemical oxidation of ethanol?

Orange dichromate (IV) ions are turned into green chromium (III) ions

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Molecular formula of ethanol

C2H6O

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Structural formula of ethanol (one used if not specified)

C2H5OH or CH3CH2OH

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What are the 2 ways ethanol is made?

Hydration of ethene
Fermentation of glucose

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Describe the process of hydration of ethene to make ethanol

Ethene gas is mixed with steam at 300oC, 65 atm pressure. Phosphoric acid (H3PO4) is used as a catalyst.

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Describe the process of fermentation to produce ethanol?

Glucose is fermented using yeast, at 30oC and under anaerobic conditions.
Mixture of ethanol and water is separated by fractional distillation at the end

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What are the conditions needed for fermentation to produce ethanol?

30oC
Absence of air (anaerobic conditions)
(Yeast needed to provide enzymes)

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Why must fermentation occur at 30oC?

Optimum temperature of enzymes. Too low would slow fermentation reaction, too high would denature enzymes

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Why must fermentation occur with an absence of oxygen?

Allows yeast to respire anaerobically, producing ethanol. Also prevents oxidation. If this didn’t occur anaerobically, CO2 and H2O would be produced.

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Conditions needed for hydration of ethene to produce ethanol?

300oC
65 atm pressure
Phosphoric acid catalyst

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Advantages of fermentation to produce ethanol

Renewable raw material used (sugar cane to provide glucose)
Condition not energy-intensive

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Word equation for fermentation to produce ethanol

Glucose —(yeast)–> ethanol + carbon dioxide

Disadvantages of fermentation to produce ethanol

Makes impure ethanol which later has to be separated by fractional distillation. Must be done in individual batches as yeast dies off when ethanol reaches 15%

Advantages of hydration of ethene to produce ethanol

Makes pure ethanol Can run continuously (not batch process)

Disadvantages of hydration of ethene to produce ethanol

Conditions require lots of energy Non-renewable raw material used (ethene gas from crude oil)

What is the functional group of carboxylic acids?

O || C - OH or -COOH

What is the display formula of ethanoic acid?

.. H O | // H - C - C | \ H O - H

Written formula of ethanoic acid

CH3COOH

What happens when carboxylic acids form salts with metals?

Loses H+ ion and becomes negatively charged Turns into ___oate instead of ___oic acid

Observations of carboxylic acids and metals

Effervescence - hydrogen gas is produced Solid disappears - metal used up in reaction

Word equation for (carboxylic) acid and metal

acid + metal --> salt + hydrogen

Word equation for reaction of methanoic acid and sodium (example)

methanoic acid + sodium --> sodium methanoate + hydrogen

Observations of carboxylic acids and metal carbonates

Effervescence - CO2 gas produced Solid disappears - Metal carbonate used up in reaction

Word equation for reaction of methanoic acid + sodium carbonate (example)

methanoic acid + sodium carbonate --> sodium methanoate + carbon dioxide + water

Word equation for reaction of (carboxylic) acid and metal carbonate

Metal + acid --> salt + carbon dioxide + water

Functional group of esters

. O || - C - O or -COO

How are esters formed?

Reaction between carboxylic acid and alcohol

What is the name of the ester formed when ethanol and ethanoic acid react together in the prescence of an acid catalyst?

ethyl ethanoate

Normal word equation for formation of an ester

carboxylic acid + ethanol --> ester + water

What is the name of the acid catalyst used for ester formation?

Concentrated sulphuric acid (H2SO4)

Displayed formula of ethyl ethanoate

.. H H O H | | || | H - C - C - O - C - C - H | | | H H H

What kind of reaction is the formation of an ester?

condensation reaction (water vapour is produced)

What are esters used for?

As food flavourings or in perfumes due to their distinctive smell

Describe how to make an ester

Mix carboxylic acid and alcohol together Add concentrated sulphuric acid (H2SO4) to act as a catalyst Warm it Tip mixture into sodium carbonate solution to neutralise the acid catalyst Wait until fizzing stops

Structural formula of ethyl ethanoate

CH3COOCH2CH3

Properties of esters/distinctive features

Volatile Fragrant/fruity smell

What are the 2 monomers used to make a polyester?

Dicarboxylic acid Diol

What kind of reaction is making polyesters?

Condensation polymerisation (water is produced)

Products when a dicarboxylic acid and a diol react together

Polyester and water

Which element(s) is lost (makes water) from an alcohol when it reacts with a carboxylic acid?

H (hydrogen)

Which element(s) is lost (makes water) from a carboxylic acid when it reacts with an alcohol?

H (hydrogen) and O (oxygen)

How are non-biodegradable polyesters disposed of?

Some are recycled Landfill Incinerated

Some polyesters are biodegradable, what does this mean?

Microbes use enzymes to break down the polymer into monomers.

Characteristics of a homologous series

Same general formula Trend in physical properties Similar chemical reactions

Word equation for hydration of ethene

ethene + water(g) --> ethanol

Describe a chemical test, other than using an indicator, to show ethanoic acid is present.

Add magnesium to the acid, effervescence will be observed.