Hey there! Sign in to join this conversationNew here? Join for free
    • Study Helper
    • Thread Starter
    Offline

    15
    ReputationRep:
    Study Helper
    I'm struggling to understand how temperature and pressure affect the yield and where the equilibrium shifts.

    The book states that the lower the temp the equilibrium shift to the right but why does this happen?

    Can anyone help?
    Offline

    14
    ReputationRep:
    (Original post by zed963)
    I'm struggling to understand how temperature and pressure affect the yield and where the equilibrium shifts.

    The book states that the lower the temp the equilibrium shift to the right but why does this happen?

    Can anyone help?
    It depends on whether the forwards reaction is exothermic or endothermic.

    Posted from TSR Mobile
    Offline

    1
    ReputationRep:
    Is the forward reaction exothermic or endothermic?

    Once you have worked this out, use Le Chatelier's Principle to work out why this is the case.

    Alternatively use the equations for entropy change, with relation to temperature and equilibrium constant, to work out for an endo or exothermic reaction, what effect changing T would have on K via delta S total.
    • Study Helper
    • Thread Starter
    Offline

    15
    ReputationRep:
    Study Helper
    (Original post by d4nny)
    Is the forward reaction exothermic or endothermic?

    Once you have worked this out, use Le Chatelier's Principle to work out why this is the case.
    Well according to the book I have to make ammonia.

    So N2+3H2 ---> 2NH3

    Forward reaction is exothermic and Backward reaction is endothermic.
    Offline

    1
    ReputationRep:
    (Original post by zed963)
    Well according to the book I have to make ammonia.

    So N2+3H2 ---> 2NH3

    Forward reaction is exothermic and Backward reaction is endothermic.
    Yes so by Le Chatelier's Principle, the reaction will appear to try to do the opposite of whatever change you make. If you cool it down, it will try and heat itself up again by favouring the forward reaction, which is exothermic, therefore making a higher yield of ammonia. i.e a shift to the right.
    • Study Helper
    • Thread Starter
    Offline

    15
    ReputationRep:
    Study Helper
    (Original post by d4nny)
    Yes so by Le Chatelier's Principle, the reaction will appear to try to do the opposite of whatever change you make. If you cool it down, it will try and heat itself up again by favouring the forward reaction, which is exothermic, therefore making a higher yield of ammonia. i.e a shift to the right.
    But if you heat the forward reaction, you'll make a higher yield of ammonia won't you?
    Offline

    1
    ReputationRep:
    (Original post by zed963)
    But if you heat the forward reaction, you'll make a higher yield of ammonia won't you?
    If you heat the reaction, it will try to oppose the change by cooling itself down and doing more of the endothermic backwards reaction. Heating will increase the RATE of the reactions, but not the yield. In industry, a compromise must be made between how quickly the ammonia forms and the yield of ammonia. The use of catalysts also helps this.

    Is this for A level?
    • Study Helper
    • Thread Starter
    Offline

    15
    ReputationRep:
    Study Helper
    (Original post by d4nny)
    If you heat the reaction, it will try to oppose the change by cooling itself down and doing more of the endothermic backwards reaction. Heating will increase the RATE of the reactions, but not the yield. In industry, a compromise must be made between how quickly the ammonia forms and the yield of ammonia. The use of catalysts also helps this.

    Is this for A level?
    Well yeah it comes into a-level but it's for GCSE because I'm taking separate sciences.
    Offline

    1
    ReputationRep:
    (Original post by zed963)
    Well yeah it comes into a-level but it's for GCSE because I'm taking separate sciences.
    Ah okay, ignore what I said about entropy in my first post about why Le Chatelier's Principle is the case, you just need to know that it is the case.
    • Study Helper
    • Thread Starter
    Offline

    15
    ReputationRep:
    Study Helper
    (Original post by d4nny)
    Ah okay, ignore what I said about entropy in my first post about why Le Chatelier's Principle is the case, you just need to know that it is the case.
    I like to understand stuff.
    Offline

    11
    ReputationRep:
    (Original post by zed963)
    But if you heat the forward reaction, you'll make a higher yield of ammonia won't you?
    All you need to know if that increasing temperature will favour the backwards reaction, i.e. the endothermic reaction in this case, so if the reaction is happening "backwards" the yield is naturally going to decrease.
    Offline

    1
    ReputationRep:
    (Original post by zed963)
    I like to understand stuff.
    Take a look at the "Le Chatelier's Principle", "The Haber Process" bits of http://www.chemguide.co.uk/physical/...bmenu.html#top

    And if you want to know more about why, go on to "Mathematical bits" and maybe look up a bit about entropy, but that is beyond GCSE so don't worry if you don't understand it yet. Take A level chemistry if you want to know in more detail
    Offline

    0
    ReputationRep:
    Did you know that the Haber Process was actually founded by a man called Balaji Sharma, on which he passed down to his cousin John Haber who took the credit? Interestingly enough, he spent 10 years studying it before deciding that a local curry establishment was more important to him. Unfortuanetly he was deported back to Sri Lanka when found to have no visa, and upon his arrival savagely attacked by a herd of goats who had taken a particular dislike to his autobiography.
    Offline

    11
    ReputationRep:
    (Original post by cheetahs56)
    Did you know that the Haber Process was actually founded by a man called Balaji Sharma, on which he passed down to his cousin John Haber who took the credit? Interestingly enough, he spent 10 years studying it before deciding that a local curry establishment was more important to him. Unfortuanetly he was deported back to Sri Lanka when found to have no visa, and upon his arrival savagely attacked by a herd of goats who had taken a particular dislike to his autobiography.
    Let's show you the door.
    • Study Helper
    • Thread Starter
    Offline

    15
    ReputationRep:
    Study Helper
    (Original post by cheetahs56)
    Did you know that the Haber Process was actually founded by a man called Balaji Sharma, on which he passed down to his cousin John Haber who took the credit? Interestingly enough, he spent 10 years studying it before deciding that a local curry establishment was more important to him. Unfortuanetly he was deported back to Sri Lanka when found to have no visa, and upon his arrival savagely attacked by a herd of goats who had taken a particular dislike to his autobiography.
    Wasn't it Fritz Haber?
    Offline

    14
    ReputationRep:
    (Original post by cheetahs56)
    Did you know that the Haber Process was actually founded by a man called Balaji Sharma, on which he passed down to his cousin John Haber who took the credit? Interestingly enough, he spent 10 years studying it before deciding that a local curry establishment was more important to him. Unfortuanetly he was deported back to Sri Lanka when found to have no visa, and upon his arrival savagely attacked by a herd of goats who had taken a particular dislike to his autobiography.
    I'd be very shocked if you take chemistry. Or atleast take it seriously.
    Offline

    0
    ReputationRep:
    (Original post by nukethemaly)
    Let's show you the door.
    Door on an online forum? Wow.

    (Original post by zed963)
    Wasn't it Fritz Haber?
    Yeah it was, John was his actual name with Fritz his nickname which is widely used.
    (Original post by popnit)
    I'd be very shocked if you take chemistry. Or atleast take it seriously.
    Yeah I take A-Level Chemistry as a joke...:rolleyes:
 
 
 
  • 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.

  • Poll
    Would you rather give up salt or pepper?
  • 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.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Write a reply...
    Reply
    Hide
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.