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A level Chemistry > Alcohol production > Flashcards

Alcohol production Flashcards

(54 cards)

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1
Q

Wha

A
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2
Q

What will we produce if we react Z-pent-2-ene with water?

A

pentan-2-ol or pentan-3-ol

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3
Q

These are examples of

A

addition reactions bcs we are adding a molecule (water) can also be called hydration reaction

& when a molecule loses water it’s a dehydration reaction

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4
Q

How do industries carry out hydration reaction?

A
  1. they add the alkene in its gas phase into the reactor
  2. they add water in the form of steam (g)
  3. add an acid catalyst (H+) to start the reaction
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5
Q

What can sulfuric acid act as?

A

electrophile

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6
Q

What happens if we react propene with water using sulfuric acid as our catalyst knowing that sulfuric acid acts as an electrophile?

A

carbon carbon bond breaks and a carbon hydrogen bond forms
causing H-O to break
making the electron pair go to Oxygen making it a long pair

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7
Q

Between these 2 molecules (propen-2-ene and propen-1-ene) what molecule would likely form

A

First molecule (propen-2-ene) as secondary carbocations are more stable than primary carbocations meaning the secondary carbocation would form majority of the time

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8
Q

Knowing that secondary is more stable, what would happen next in the mechanism?

A

because we are also reacting water
a water bond would form between the carbocation like this
arrow telling us C—O bond forms

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9
Q

What happens next after water bonds with the molecule of propene

A

The Lone pair attracts one of the H+ ions and forms a bond breaking the H—O bond

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10
Q

The complete mechanism memorise

from propene to propan-2-ol

A
  1. catalyst H forms a bond with the double bond of carbon forming a carbocation
  2. carbocation forms a bond with water
  3. lone pair of catalyst forms a bond of one Hydrogen and that hydrogen breaks the bond with oxygen
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11
Q

Because sulfuric acid is a reagent at the beginning of the reaction and a product at the end, its acting as a

A

catalyst

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12
Q

because H2SO4 (sulfuric acid) is acting as an electrophile, this is an example

A

of electrophilic addition reaction

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13
Q
A

mechanism of all reactions using sulfuric acid

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14
Q

How do we simplify this to make it easier rather than writing whole sulfuric acid out?

A

H+

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15
Q

What’s the most appropriate mechanism for this reaction?

A

As the acid wasn’t specified this is the correct answer

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16
Q

What’s wrong with this mechanism?

A

1) arrow is the other way around
2) Oxygen is missing a lone pair
3) Oxygen is missing a + bcs it has 3 bonds

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17
Q

What’s the equation for this reaction

A

CH2=CHCH2CH2CH3+H2O <=> CH3CH(OH)CH2CH2CH3

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18
Q

What’s the equation for the hydration of butene?

A

C4H8 + H2O <=> C4H9OH

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19
Q

What do we do when writing equations for ethene, propene and ethanol?

A

we just write their molecular formula as they don’t have position isomer

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20
Q

What’s the equation for the hydration of propene to propan-1-ol

A

C3H6 + H2O <=> CH3CH2CH2OH

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21
Q

Industries use a degree of 300 celsius which is a compromised temperature why is that so?

A

this reaction is exothermic as stated (-45 kJmol)
so if we lower the temperature the equilibrium position will shift to the right
and increase the yield of ethanol
However low temperatures also decrease the rate of reaction so industries use 300 as a compromise between yield and rate

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22
Q

Why does ethanol form in this reaction?

& when does it form a liquid

Study These Flashcards
A

because of the high temperature which causes the ethanol to come out as a gas
it forms a liquid when it leaves the reactor and enters the condenser when it’s a liquid

23
Q

To produce ethanol from ethene industries use

Study These Flashcards
A

H3PO4 (phosphoric) as a catalyst
compromised Temperature of 300
compromised Pressure if 6000 kPA

24
Q

What’s the equation for the hydration of ethene?

Study These Flashcards
A

C2H4 + H2O <=> C2H5OH

25
What’s the equation for the hydration of but-2-ene to butan-2-ol?
A
26
which of these molecules is the major product in the dehydration reaction of pent-1-ene? and why
C to form pentan-1-ol, a primary carbocation intermediate must form. however to form pentan-2-ol, a secondary carbocation must form.
27
what do catalyst do industries use to produce ethanol from ethene. what are the conditions?
catalysts use Phosphoric acid H3PO4 they use compromised temperatures between 300 and 600 and compromised pressures between 5000 and 10000
28
Why do industries use compromised temperatures and pressure when producing ethanol from ethene?
The higher the pressure, the more dangerous the conditions, the higher the yield of ethanol, the more expensive the conditions The higher the temperature, the lower the ethanol yield, the faster the rate of reaction, the more expensive the conditions The reaction of ethene with water is exothermic. industries use a compromised temperature for ethanol because high temperatures increase the rate of reaction but lower the yield of ethanol. In the reaction of ethene with water, there are 2 moles of reactants and one mole of product. Industries use a compromise pressure because high pressure increase the yield of ethanol but they also increase the risk of explosion
29
How can else can ethanol be produced?
By fermentation where ethanol can be produced from sugar To produce ethanol from sugar we add warm water to sugar and add a single cell fungus (yeast) and make sure that there’s no oxygen in the system so we seal the mixture we call ethanol produced from fermentation a biofuel leave the mixture to produce ethanol and carbon dioxide
30
why do we can ethanol produced from fermentation a biofuel?
because it’s made from biological resources
31
What’s the sugar called in fermentation?
Sucrose
32
When sucrose is added to warm water what does it break into?
it breaks into 2 molecules | glucose and fructose
33
Out of the sugars it broke down in, | what forms ethanol in the process of fermentation?
glucose reacts to form ethanol and carbon dioxide
34
What is the balanced equation for fermentation?
35
What in yeast makes the glucose break down
enzymes produce by yeast catalyst reaction of glucose to produce ethanol and carbon dioxide
36
Above a certain concentration, ethanol is toxic to yeast. So what concentration do we need?
To keep our yeast alive and working we need a low concentration of ethanol We do this by removing ethanol when it’s formed.
37
What can we use to seperate ethanol from the reaction?
distillation, because ethanol has a lower boiling point than our sugars solution. We seperate ethanol from out reaction mixture using distillation
38
What do we need to ensure during fermentation?
that there’s no oxygen present in the system fermentation is carried out in the absence of oxygen
39
What are the conditions of fermentation reactions?
we carry them out in the absence of water and keep the temperatures between 25-40 degrees celsius
40
Ethanol produced by hydration is made from
crude oil which is a non renewable fossil fuel
41
ethanol produced from fermentation is made from
plants which are renewable
42
Why is the equipment used for fermentation much cheaper?
to produce ethanol from hydration we need to extract it from the ground, then undergoes fractional distillation and then cracked which are all expensive requirements whereas to produce ethanol from fermentation we just need to grow and harvest the plants and produce yeast so overall fermentation is much cheaper equipment wise
43
Compared to fermentation, why is hydration less sustainable?
Fermentation only requires plants which won’t run out, whilst hydration requires crude oil which will run low so fermentation is more sustainable
44
Compared to hydration and fermentation, which one is energy sufficient
hydration requires temperatures of 300 C and 6000 kPA whereas fermentation only requires 25-40 degree and standard pressure conditions meaning we need far less energy to manage fermentation and cost will be way cheaper
45
What are the advantages of hydration compared to fermentation?
Temperatures used for fermentation (25-40) is much lower than hydration (300) meaning hydration will have a higher rate of reaction so hydration produces ethanol quicker than fermentation (slower) when we produce ethanol from fermentation we produce ethanol and carbon dioxide whereas if we produce ethanol from hydration we just produce ethanol meaning hydration has a higher atom economy (100%) so hydration is more efficient at producing ethanol than fermentation ( <100%) ``` when fermentation (batch process) is being done we need to clean it each time so we need to manually stop and keep going & only collect ethanol in batches whereas hydration when ethene is added to water in the reactor n reacts with acid catalyst ethanol is seperated and condensed and any remaining ethene or steam returns to the reactor so it means it can run continuously without stopping hydration = continuous process which is another reason why its faster ```
46
compare fermentation and hydration, | what process is better?
fossil fuel will run out | in the long term fermentation is better
47
what’s the molecular form for glucose
C6H12O6
48
when fuels completely combust what does it form?
CO2 and H2O
49
What is carbon neutral defined as in terms of biofuels
No overal CO2 emission into the atmosphere
50
What’s the equation for photosynthesis
6CO2 + 6H2O —> C6H12O6 + 6O2
51
What’s the equation of fermentation
C6H12O6 —> 2C2H5OH + 2CO2
52
What’s the equation for complete combustion
2C2H5OH + 6O2 —> 4CO2 + 6H2O
53
What if we combine all photosynthesis, fermentation and complete combustion equation what would it look like ?
bcs of the repeat Carbon dioxide bio-ethanol is carbon neutral but in reality it’s not completely due to CO2 being released during fertiliser production, when it’s transported and when plants are harvested
54
state the meaning of the term biofuel
biological resources 

A level Chemistry (12 decks)

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