Alcohols

Question 1

Molecular formula of methanol.

Answer 1

CH₃OH

Question 2

Molecular formula of ethanol.

Answer 2

C₂H₅OH

Question 3

Molecular formula of propanol.

Answer 3

C₃H₇OH

Question 4

Molecular formula of butanol.

Answer 4

C₄H₉OH

Question 5

Molecular formula of pentanol.

Answer 5

C₅H₁₁OH

Question 6

What is the general formula for alchohols?

Answer 6

C_nH_2n+1OH

Question 7

Ethanol is made by the process of fermentation:

Answer 7

glucose → ethanol + carbon dioxide

Question 8

The balanced symbol equation for fermentation:

Answer 8

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂

Question 9

How is ethanol made by the fermentation of glucose solution?

Answer 9

• The reaction is catalysed by the enzymes in yeast.
• This will only happen if there is no oxygen present.
• The dilute liquid produced undergoes fractional distillation to produce ethanol.

Question 10

Only ethanol is made by fermentation, under carefully controlled conditions.

Answer 10

• If the temperature is low, the enzyme in yeast are inactive.
• If the temperature is too high, the enzymes in yeast are denatured.
• If air is present, there is a different reaction, producing ethanoic acid instead of ethanol.

Question 11

Uses of ethanol made by fermentation.

Answer 11

Ethanol made by fermentation can also be used as a fuel. It is a renewable fuel because the plants that make the sugar for the processes can be grown very quickly.

Question 12

Producing ethanol by hydration

Answer 12

• Ethanol that is used in industry can also be made from ethene. Ethanol made in this way is a non renewable fuel because the ethene it is made from, comes from fossil fuels. These fossil fuels cannot be replaced and are a finite resource.
• The reaction to make ethanol from ethene is known as a hydration reaction because water is added to the ethene molecule: ethene + water ⇒ ethanol.
• Ethene and steam are passed over a hot phosphoric acid catalyst.

Question 13

Ethane symbols

Answer 13

C₂H₄

Question 14

The balanced symbol Eq. for the hydration reaction is:

Answer 14

C₂H₄ + H₂O ⇒ C₂H₅OH

Question 15

Ethanol production by fermentation advantages and disadvantages

Answer 15

• Conditions: 35 ºC less energy needed
• Processing: Batch
• Sustainability: Sustainable
• Purification: Fractional distillation needed
• Percentage yield and atom economy: Low yield and atom economy

Question 16

Ethanol production by hydration advantages and disadvantages

Answer 16

• Conditions: Hot catalyst, more energy needed
• Processing: Continuous
• Sustainability: From a finite source
• Purification: Relatively pure on production
• Percentage yield and atom economy: high yield and high economy