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WJEC A-Level Chemistry > 2. 7 Alcohols and Carboxylic Acids > Flashcards

2. 7 Alcohols and Carboxylic Acids Flashcards

1
Q

What is the functional group of alcohols?

A

-OH

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2
Q

What is the general formula for alcohols?

A

C(n)H(2n+1)OH

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3
Q

What are the conditions for the industrial production of ethanol from ethene?

A

Hydration of ethene:
- Phosphoric acid catalyst (aqueous)
- Temperature of 300oC and high pressure

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4
Q

Write the chemical equation for the hydration of ethene

A
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5
Q

How can ethanol be produced from a renewable source?

A

Ethanol can be produced from the fermentation of sugars. In crops, enzymes break down starch into sugars which can then undergo fermentation to form ethanol.

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6
Q

What conditions are required for the fermentation of glucose to form ethanol?

A
  • Carried out with yeast
  • 30-40oC temperature
  • Anaerobic conditions (no oxygen)
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7
Q

What is the chemical equation for the fermentation of glucose to form ethanol?

A

C(6)H(12)O(6) → 2C(2)H(5)OH + 2CO(2)

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8
Q

After fermentation, how can ethanol be separated from the rest of the reaction mixture?

A

Distillation

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9
Q

Why is the production of ethanol fuel from glucose said to be ‘carbon neutral’?

A

A process is carbon neutral if it contributes no net increase to the amount of carbon dioxide in the atmosphere.
Ethanol fuel, produced from glucose, is carbon neutral because the crops take in carbon dioxide during photosynthesis which balances out the amount of carbon dioxide that is released when the fuel is burned.

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10
Q

Why might someone argue that the production of ethanol fuel from glucose is not carbon neutral?

A

Energy is required to power the machinery to make fertilisers for the crops and to harvest the crops, which releases carbon dioxide. Similarly, more carbon dioxide is released during the transportation of the ethanol.

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11
Q

What is formed when alcohols undergo dehydration?

A

Alkenes

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12
Q

How do alcohols undergo dehydration reactions?

A

Alcohols undergo dehydration reactions to form an alkene and a water molecule.
There are two ways to carry out dehydration:
- Heat with strong acid catalyst.
- Pass alcohol vapour over Al2O3 powder.

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13
Q

What is the chemical equation for the dehydration of propan-2-ol to form prop-2-ene?

A
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14
Q

Explain the classification of alcohols

A
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15
Q

How are primary alcohols oxidised to carboxylic acids?

A

If a primary alcohol is heated under reflux with acidified potassium dichromate(VI), the alcohol will be oxidised form a carboxylic acid.
CH(3)CH(2)OH + 2[O] → CH(3)COOH + H(2)O
The acidified potassium dichromate(VI) will change colour from orange to green.

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16
Q

How are secondary alcohols oxidised to ketones?

A

If a secondary alcohol is heated under reflux with acidified potassium dichromate (VI), the alcohol will be oxidised to form a ketone:
CH(3)CH(OH)CH(3) + [O] → CH(3)COCH(3) + H(2)O
The acidified potassium dichromate(VI) will change colour from orange to green.

17
Q

What qualitative test can be carried out to test for primary and secondary alcohols?

A

Add acidified potassium dichromate(VI):
The solution will change colour from orange to green if a primary or secondary alcohol is present.

18
Q

What qualitative test can be carried out to test for carboxylic acids?

A

Add sodium hydrogencarbonate (NaHCO3):
The solution will effervesce and carbon dioxide will be produced if a carboxylic acid is present. The gas released can be tested with limewater to identify it as carbon dioxide.

19
Q

What is produced when carboxylic acids react with bases?

A

Salt and water

20
Q

What is the chemical equation for the reaction of ethanoic acid with sodium hydroxide?

A
21
Q

What is produced when carboxylic acids react with carbonates?

A

Salt, carbon dioxide and water

22
Q

What is the chemical equation for the reaction of methanoic acid with sodium carbonate?

A
23
Q

What is produced when carboxylic acids react with hydrogencarbonates?

A

Salt, carbon dioxide and water

24
Q

What is the chemical equation for the reaction of ethanoic acid with sodium hydrogencarbonate?

A
25
Q

How do alcohols react with carboxylic acids?

A

Alcohols react with carboxylic acids to form esters. This process is called esterification and requires heating with a sulfuric acid catalyst.

26
Q

What is the chemical equation for the reaction between methanol and ethanoic acid? Give the name of the ester formed

A
27
Q

Explain how ethanol can be separated from water

A

Ethanol and water have different boiling points so they can be separated by distillation:
- The mixture is heated until the ethanol evaporates.
- The ethanol vapours enter the condenser where
they condense and run into a beaker.

WJEC A-Level Chemistry (35 decks)

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