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AQA A-Level Chemistry- Adeebah > Alcohols > Flashcards

Alcohols Flashcards

1
Q

State the test to distinguish an alcohol from a carboxylic acid?

A

Add sodium hydrogen carbonate

Carboxylic acid: Effervescence
Alcohol: No reaction

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2
Q

How is biofuel ethanol purified?

A

Using fractional distillation

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3
Q

Why has direct hydration of ethene replaced the fermentation method?

A

The direct hydration does not require a catalyst

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4
Q

Which compound is formed when 1-phenylethanol reacts with acidified potassium dichromate?

A

C6H5COCH3
(Phenyl group) + ( C=O ketone)

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5
Q

How to test alcohol has been dehydrated into alkene?

A

Add bromine water
The solution will turn colourless if alkene is present

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6
Q

Why is sodium carbonate added to the distillate in the dehydration of alcohols involving phosphoric acid?

A

To neutralise the phosphoric acid

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7
Q

Give a property of anhydrous calcium chloride that allows it to act as a drying agent in dehydration of alcohols?

A

Anhydrous-absorbs water
Does not react with alkene

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8
Q

Where is the OH group in a primary alcohol?

A

At the end of the chain

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9
Q

Where is the OH group in a secondary alcohol?

A

In the body of the chain

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10
Q

Where is the OH group in a tertiary alcohol?

A

At a branch in the chain

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11
Q

How many R groups does a primary alcohol have?

A

1

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12
Q

How many R groups does a secondary alcohol have ?

A

2

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13
Q

How many R groups does a tertiary alcohol have?

A

3

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14
Q

How are alcohols classified?

A

Primary, secondary, tertiary according to how many R groups are bonded to the carbon that has the OH group.

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15
Q

Why are short chain alcohols soluble in water?

A

Soluble due to hydrogen bonding predominating

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16
Q

Why are long chain alcohols insoluble in water?

A

Non-polar hydrocarbon chain dominates and so alcohol is insoluble in water.

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17
Q

How is ethanol made by fermentation? (Reaction)

A

Glucose -> ethanol + carbon dioxide

18
Q

How is ethene produced at present?

A

Crude oil fractions are cracked , ethene is hydrated so water is added across the double bond

19
Q

Disadvantages of ethene production by fermentation

A

-slow rate of reaction
- aqueous solution of ethanol is produced rather than pure
- requires batches rather than continuous production

20
Q

Advantages of making ethene by carbohydrates (fermentation)

A

Renewable
Can be viewed as carbon neutral.

21
Q

Advantages of ethene production by crude oil?

A

Fast rate of reaction
Continuous process
Essentially pure product

22
Q

Disadvantages of ethene production by crude oil?

A

Non renewable - as crude oil is finite resource
Releases CO2

23
Q

General Equation for the complete combustion of alcohols ?

A

Alcohol + oxygen -> carbon dioxide and water

24
Q

What type of reaction are alcohols involved in?

A

Elimination reactions
Specifically Dehydration as water is lost

25
Q

Give two dehydrating agents for alcohols?

A

Phosphoric acid
Sulfuric acid

26
Q

What can elimination reactions of longer or branched alcohols form?

A

Mixture of alkenes including E/Z isomers

27
Q

What are primary alcohols oxidised to?

A

Aldehydes ( C=O at the end and H at the end )

28
Q

What can aldehydes be oxidised to?

A

Carboxylic acids ( C=O bond at end and OH at the end )

29
Q

What are Secondary alcohols oxidised to?

A

Ketones ( C=O group within carbon chain)

30
Q

Can tertiary alcohols be oxidised and why?

A

Not easily oxidised
Need C-C bond to break

31
Q

What solution is added to oxidise alcohols to aldehydes and ketones?

A

Potassium dichromate,acidified with dilute sulphuric acid

32
Q

What does potassium dichromate act as in the oxidising of alcohols ?

A

Oxidising agent

33
Q

What colour change is show in the oxidation of alcohols to aldehydes/ ketones

A

Orange to green

34
Q

Tests for aldehydes and ketones?

A

The tollens (silver mirror) test- silver nitrate in aqueous ammonia
The fehlings test - blue copper solution

35
Q

Positive result for tollens with aldehyde ?

A

Silver mirror formed

36
Q

Positive result for fehlings with aldehyde?

A

Blue -> brick red precipitate

37
Q

Disadvantages of production of ethanol by fermentation?

A

Transport (petrol car engines would have to be modified to use fuels with high ethanol conc)
This burns fuel that releases CO2

Extracting/ planting / harvesting which burns fuel that releases CO2

38
Q

Why can ethanol production by fermentation be deemed carbon neutral?

A

CO2 released when it is burnt is balanced by CO2 absorb by the plant

39
Q

Conditions of ethanol production by fermentation?

A

Anaerobic - used glucose
30-40 degrees
Yeast - converts sugar into glucose

40
Q

Balanced reaction for industrial fermentation of glucose ?

A

C6H12O6 —> 2 C2H5OH + 2CO2

AQA A-Level Chemistry- Adeebah (7 decks)

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