souless_lol
Badges: 3
Rep:
?
#1
Report Thread starter 4 years ago
#1
For those of you who are doing the aqa C3 and C2 exam tomorrow, can someone kindly explain The Haber Process and Chemical Equilibrium please I still don't understand it!
Thanks i'll love you forever
0
reply
semenovarvara
Badges: 0
Rep:
?
#2
Report 4 years ago
#2
Reversible reaction is in equilibrium when the rate of the forward reaction is equal to the rate of the backward reaction. This can only happen in the closed system.

As for altering conditions in the equilibrium: I just memorised that if there are more molecules on the right side then the pressure needs to be decreased to increase the amount of products (and the other ways round).

Also if the forward reaction is exothermic you need to lower the temperature to increase the amount of product (and the other way round).
If you memorise those two rules it will be easy to figure out how any change will affect the amount of product.
I didn't even try to understand it tbh it's probably the most complicated thing in c3, at least for me
0
reply
spnlove
Badges: 2
Rep:
?
#3
Report 4 years ago
#3
(Original post by souless_lol)
For those of you who are doing the aqa C3 and C2 exam tomorrow, can someone kindly explain The Haber Process and Chemical Equilibrium please I still don't understand it!
Thanks i'll love you forever
Okay so chemical equilibrium happens if a reversible reaction happens in a closed system (i.e. no substances escape) and it's when the forward reaction and backwards reaction happen at the same rate so the amounts of reactants and products reach a balance.
You can change the temperate and pressure to move the position of the equilibrium meaning that you can make it so more products are formed or more reactants are formed.
CHANGING THE TEMP. : In a reversible reaction, one reaction will be exothermic and the other will be endothermic.
- If the temp. is increased, the equilibrium will shift towards the endothermic reaction (so if the backwards reaction was endothermic, then more of the reactants would be produced, the equilibrium would shift to the left).
- If the temp. is decreased, the equilibrium will shift towards the exothermic reaction

CHANGING THE PRESSURE:
- If you increase the pressure, the equilibrium will shift towards the side with less molecules in it
- If you decrease pressure, equilibrium will shift towards the side with more molecules in it
In the mark schemes, you usually get marks for saying how many molecules are on each side of the reaction.


Basically, I think about it as whatever you change, the equilibrium will do the opposite (if you lower the pressure, equilibrium will shift towards the side of the reaction where there's more and it's the same for temp. if you think about the endothermic reaction being 'colder' as it's taking in energy). Oh and catalysts don't do anything to change the position of equilibrium.

THE HABER PROCESS: This process creates ammonia from nitrogen and hydrogen. Nitrogen is taken from the air and the hydrogen comes from natural gas. It's a reversible reaction:

N2 + 3H2 ⇌ 2NH3

It is produced at high pressure of 200 atmospheres because high pressures will favour the forward reaction as there are less molecules on that side (there are 4 on the left but only 2 on the right). This means a higher % yield will be found without making it too expensive.

It's produced at 450 degrees. This is because the forward reaction is exothermic so to get the best yield you'd have to lower the temperature but this would mean the rate of reaction would be less. So 450 degrees celsius is a comprimise. To speed up the reaction they also use an iron catalyst.

The ammonia is formed as a gas but it enters a condenser where it gets cooled and liquified so it can be removed easily. Then the unused hydrogen and nitrogen are recycled ready to be used again.

This is a quite a helpful image of the process:



Sorry this is so long, I hope it helped and good luck!
Attached files
0
reply
souless_lol
Badges: 3
Rep:
?
#4
Report Thread starter 4 years ago
#4
(Original post by semenovarvara)
reversible reaction is in equilibrium when the rate of the forward reaction is equal to the rate of the backward reaction. This can only happen in the closed system.

As for altering conditions in the equilibrium: I just memorised that if there are more molecules on the right side then the pressure needs to be decreased to increase the amount of products (and the other ways round).

Also if the forward reaction is exothermic you need to lower the temperature to increase the amount of product (and the other way round).
If you memorise those two rules it will be easy to figure out how any change will affect the amount of product.
I didn't even try to understand it tbh it's probably the most complicated thing in c3, at least for me
aw thank you so much
0
reply
souless_lol
Badges: 3
Rep:
?
#5
Report Thread starter 4 years ago
#5
(Original post by spnlove)
Okay so chemical equilibrium happens if a reversible reaction happens in a closed system (i.e. no substances escape) and it's when the forward reaction and backwards reaction happen at the same rate so the amounts of reactants and products reach a balance.
You can change the temperate and pressure to move the position of the equilibrium meaning that you can make it so more products are formed or more reactants are formed.
CHANGING THE TEMP. : In a reversible reaction, one reaction will be exothermic and the other will be endothermic.
- If the temp. is increased, the equilibrium will shift towards the endothermic reaction (so if the backwards reaction was endothermic, then more of the reactants would be produced, the equilibrium would shift to the left).
- If the temp. is decreased, the equilibrium will shift towards the exothermic reaction

CHANGING THE PRESSURE:
- If you increase the pressure, the equilibrium will shift towards the side with less molecules in it
- If you decrease pressure, equilibrium will shift towards the side with more molecules in it
In the mark schemes, you usually get marks for saying how many molecules are on each side of the reaction.


Basically, I think about it as whatever you change, the equilibrium will do the opposite (if you lower the pressure, equilibrium will shift towards the side of the reaction where there's more and it's the same for temp. if you think about the endothermic reaction being 'colder' as it's taking in energy). Oh and catalysts don't do anything to change the position of equilibrium.

THE HABER PROCESS: This process creates ammonia from nitrogen and hydrogen. Nitrogen is taken from the air and the hydrogen comes from natural gas. It's a reversible reaction:

N2 + 3H2 ⇌ 2NH3

It is produced at high pressure of 200 atmospheres because high pressures will favour the forward reaction as there are less molecules on that side (there are 4 on the left but only 2 on the right). This means a higher % yield will be found without making it too expensive.

It's produced at 450 degrees. This is because the forward reaction is exothermic so to get the best yield you'd have to lower the temperature but this would mean the rate of reaction would be less. So 450 degrees celsius is a comprimise. To speed up the reaction they also use an iron catalyst.

The ammonia is formed as a gas but it enters a condenser where it gets cooled and liquified so it can be removed easily. Then the unused hydrogen and nitrogen are recycled ready to be used again.

This is a quite a helpful image of the process:



Sorry this is so long, I hope it helped and good luck!
Oh my gosh i actually understood something in like 5 minutes! Thank you so so much for this I really appreciate it
0
reply
staro62
Badges: 2
Rep:
?
#6
Report 4 years ago
#6
looking at all this i need to revise
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • Sheffield Hallam University
    Get into Teaching in South Yorkshire Undergraduate
    Wed, 26 Feb '20
  • The University of Law
    Solicitor Series: Assessing Trainee Skills – LPC, GDL and MA Law - London Moorgate campus Postgraduate
    Wed, 26 Feb '20
  • University of East Anglia
    PGCE Open day Postgraduate
    Sat, 29 Feb '20

People at uni: do initiations (like heavy drinking) put you off joining sports societies?

Yes (476)
66.48%
No (240)
33.52%

Watched Threads

View All