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Chemistry A level > Alcohols > Flashcards

Alcohols Flashcards

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1
Q

What are the bond angles in alcohols?

A

H-C-H bonds and C-C-O are 109.5
H-O-C bond is 104.5

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2
Q

What is the boiling point of alcohols?

A
  1. Relatively low volatility and high bp
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3
Q

Why do alcohols have high BP?

A
  1. Ability to form H-bond between alcohol molecules
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4
Q

Why can smaller alcohols dissolve in water?

A

Can form h-bonds to water molecules

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5
Q

What is the oxidising agent that causes alcohols to oxidise?

A

Potassium dichromate

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6
Q

Describe the partial oxidation of primary alcohols

A

Reaction: Primary alcohols to aldehyde
Reagent: potassium dichromate (VI) and dilute sulfuric acid
Conditions: warm gently and distil out the aldehyde as it forms

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7
Q

What is the observation for oxidising alcohols?

A

Orange dichromate ion reduces to green Cr3+ ion

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8
Q

What are the two ways ethanol can be produced?

A
  1. Hydration of ethene
  2. Fermentation
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9
Q

Describe hydration of ethene?

A

Reagent: Excess steam
Catalyst: concentrated h3po4
Conditions: high temperature, high pressure (60 atm), excess steam
Mechanism: electrophilic addition

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10
Q

Why is high pressure used in hydration?

A
  1. Equilibrium shifts to the right as there are fewer gaseous molecules
  2. Yield of alcohol increases
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11
Q

What is a biofuel?

A

A fuel produced from plants

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12
Q

What are the conditions for fermentation?

A
  1. Anaerobic
  2. 37 degrees
  3. Yeast
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13
Q

Why are anaerobic conditions used for fermentation?

A

Oxygen from air is kept out to prevent oxidation of ethanol to ethanoic acid

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14
Q

Give an advantage and a disadvantage of carrying fermentation at higher temperatures

A

Advantage: ethanol is produced at a faster rate
Disadvantage: more energy is used

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15
Q

How is pure ethanol obtained from industrial fermentation?

A
  1. Use fractional distillation to separate water and ethanol
  2. They have different BP
  3. The BP of water is 100 degrees and ethanol is 78 degrees
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16
Q

What is the raw material used in hydration of ethene

A

Ethene from crude oil- non renewable

17
Q

What is the raw material used in fermentation?

A

Sugar- renewable

18
Q

Is the product of hydration if ethene pure or impure?

A

Pure

19
Q

Is the product of fermentation pure or impure

A

Impure - requires fractional distillation

20
Q

What is the ROR of hydration of ethene

A

Fast

21
Q

What is the ROR of fermentation

A

Slow

22
Q

Describe the process of hydration of ethene and fermentation

A

Hydration of ethene - continuous
Fermentation - batch

23
Q

What is the cost of hydration of ethene?

A

High set up cost/ low labour costs

24
Q

What is the cost of fermentation

A

Low set up costs/ high labour costs

25
Q

Define the term carbon neutral

A

No overall carbon dioxide emission to the atmosphere

26
Q
  1. Photosynthesis
  2. Fermentation
  3. Combustion

Q) explain why the ethanol produced may not be a carbon neutral biofuel

A

CO2 is released during planting, harvesting and transport as it burns fuels that release CO2

27
Q

What is the role of dichromate ions?

A

Oxidising agent ( electron acceptor)

28
Q

What is the observation with Fehling’s or Benedict’s solution for ketones?

A

Stays blue ( no visible change)

29
Q

What is the observation with Tollen’s reagent for ketones?

A

No visible change, stays colourless

30
Q

What is the observation with Fehling’s solution for an aldehyde

A

Blue to brick red ppt

31
Q

What is the observation with Tollen’s reagent for an aldehyde

A

Colourless solution forms a silver mirror

32
Q

How do you test for carboxylic acids

A

Reagent: solid sodium carbonate
Observation: effervescence/ bubbles

33
Q

Outline the mechanism of elimination?

A

Reagent: concentrated sulfuric acid or phosphoric acid
Conditions: heat/warm

34
Q

What does the elimination do?

A

Remove water molecule from alcohol to form alkene

Chemistry A level (4 decks)

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