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

    15
    ReputationRep:
    When do you the energy balance equation which includes Delta U and when do you use the form with Delta H.
    • PS Reviewer
    Offline

    18
    ReputationRep:
    (Original post by jonnypdot)
    When do you the energy balance equation which includes Delta U and when do you use the form with Delta H.
    Are you referring to changes in enthalpy \Delta H and internal energy \Delta U?

    If so, you need to know the relation:

    \Delta H = \Delta U + P \Delta V

    If your system experiences a change in volume, consider the change in enthalpy. If not, you only need to consider a change in internal energy.
    • Thread Starter
    Offline

    15
    ReputationRep:
    (Original post by pleasedtobeatyou)
    Are you referring to changes in enthalpy \Delta H and internal energy \Delta U?

    If so, you need to know the relation:

    \Delta H = \Delta U + P \Delta V

    If your system experiences a change in volume, consider the change in enthalpy. If not, you only need to consider a change in internal energy.
    change in volume in what sense, a reactor would have a fixed volume. I can see the point you made from the equation you have given.
    • PS Reviewer
    Offline

    18
    ReputationRep:
    (Original post by jonnypdot)
    change in volume in what sense, a reactor would have a fixed volume. I can see the point you made from the equation you have given.
    Essentially, it's when your system boundary changes. One well-known example is that of a balloon expanding.
 
 
 
  • 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
    What newspaper do you read/prefer?
  • 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

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