3.3.5.1 Alcohol production

Question 1

Why do alcohols have higher melting point than alkanes of the same length?

Answer 1

OH in alcohols causes hydrogen bonding which increases the intermolecular forces. Therefore more energy is needed to overcome these forces which increases the melting point

Question 2

Are alcohols soluble?

Answer 2

The OH group of alcohols can hydrogen bond to water molecules but the non-polar hydrocarbon chain cannot, so alcohols with short chains are soluble

Question 3

How is ethanol produced from cracking?

Answer 3

Ethene is produced when crude oil fractions are cracked
Ethene is hydrated which means that water is added across the double bond
Phosphoric acid catalyst

Question 4

How is ethanol produced by fermentation?

Answer 4

Glucose = Ethanol + Carbon Dioxide
Carbohydrates broken down into sugars
Converted into ethanol by yeast
Carbohydrates come from crops e.g. sugar cane
Anaerobic respiration
35 degrees celcius: too low would be slow, too high would denature the enzyme
Air kept out to stop ethanol from being oxidised to ethanoic acid
At 15% ethanol, enzymes are unable to function. Ethanol can be distilled by fractional distillation

Question 5

What is the formula for glucose?

Answer 5

C6H12O6

Question 6

What is the process of making ethanol from crude oil with mechanisms?

Answer 6

See card
Step 1: from the double bond to the hydrogen ion
Step 2: from electronegative oxygen to positive carbon atom
Step 3: from O - H bond to oxygen atom
Forms ethanol plus hydrogen

Question 7

What are the advantages and disadvantages of biodiesel?

Answer 7

Releases less carbon dioxide than mineral diesel from crude oil
Fully degradable so is less damaging when spilt
Not carbon neutral as energy is required for processing, farming and fertiliser manufacture
More expensive to produce than fossil fuels

Question 8

What are the advantages and disadvantages of bioethanol?

Answer 8

CO2 release is lower than fossil fuels
Renewable
Less energy dense than petrol
Cutting down trees to provide area for growing plants destroys wildlife

Question 9

What are the advantages and disadvantages of hydrogen?

Answer 9

The only product is water so there are no polluting gases
It is an infinite resource
It is expensive to electrolyse water
Electricity is required to produce hydrogen

Question 10

What are the properties of alcohols?

Answer 10

Normally polar molecules
Soluble in water
High melting/boiling points compared to alkenes/alkanes of a similar size

Question 11

What is the primary, secondary and tertiary structures of alcohols?

Answer 11

See card

Question 12

Fuel cells

Answer 12

Produce electricity from the reaction between hydrogen and oxygen
Efficient at transferring the energy of the reaction
Cars with fuel cells are expensive

Question 13

What is the reaction between alkenes and steam?

Answer 13

Alkene + H2O = Alcohol

Question 14

What are the conditions for the reaction between ethene and steam?

Answer 14

Ethene + steam (+ phosphoric acid catalyst) = ethanol

Question 15

What is the reaction for anaerobic respiration?

Answer 15

C6H12O6 ( + yeast ) = 2C2H5OH + 2CO2

Question 16

What are the conditions for the breakdown of glucose?

Answer 16

Rate is affected by temperature
Enzyme denatures at high temperatures
Air kept out to prevent oxidation so that ethanoic acid is not produced
Ethanol is extracted by fractional distillation