Turn on thread page Beta
    • Thread Starter
    Offline

    16
    ReputationRep:
    1). Two enthalpy changes of reaction are shown below.

    N_{2(g)} + 3H_{2(g)} \rightarrow 2NH_{3(g)} \Delta H = -92kJ mol^{-1}
    N_2O_{4(g)}\rightarrow 2NO_{2(g)}\Delta H = +54kJ mol^{-1}

    What is the enthalpy change of reaction for the following:

    \frac{1}{2}N_{2(g)} + \frac{3}{2}H_{2(g)}\rightarrow NH_{3(g)}
    \frac{1}{2}N_2O_{4(g)}\rightarro  w NO_{2(g)}

    We haven't been given any equations or anything to work it out so I have no idea how to do it =\ .
    Offline

    2
    ReputationRep:
    They are equivalent...?
    Offline

    11
    ReputationRep:
    (Original post by ViralRiver)
    1). Two enthalpy changes of reaction are shown below.

    N_{2(g)} + 3H_{2(g)} \rightarrow 2NH_{3(g)} \Delta H = -92kJ mol^{-1}
    N_2O_{4(g)}\rightarrow 2NO_{2(g)}\Delta H = +54kJ mol^{-1}

    What is the enthalpy change of reaction for the following:

    \frac{1}{2}N_{2(g)} + \frac{3}{2}H_{2(g)}\rightarrow NH_{3(g)}
    \frac{1}{2}N_2O_{4(g)}\rightarro  w NO_{2(g)}

    We haven't been given any equations or anything to work it out so I have no idea how to do it =\ .
    As enthalpy of formation for elements in their standard states are zero, that means your enthalpy for each of the reaction is simply the enthalpy of formation of the product, ie NH3 and NO2.

    But your values in your first part are given in kJ per mol of product formed already, so the values for the second part is for 1 mol of the corresponding products and hence should be the same.

    If however, the enthalpy for the first reaction is asked, it'd be 2x(-92) because you are producing 2 mol of NH3. Hope you are getting the hang of it.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: January 27, 2010

University open days

  1. University of Bradford
    University-wide Postgraduate
    Wed, 25 Jul '18
  2. University of Buckingham
    Psychology Taster Tutorial Undergraduate
    Wed, 25 Jul '18
  3. Bournemouth University
    Clearing Campus Visit Undergraduate
    Wed, 1 Aug '18
Poll
How are you feeling in the run-up to Results Day 2018?

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.