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

    9
    ReputationRep:
    (Original post by Peroxidation)
    Yea that is confusing. I think they're either trying to put something in layman's terms and ruining the science in the process, or they just don't know what they're talking about. There's only really 1 way for liquid to gas changes of state and that's boiling. Obviously there's evaporation too, but that's effectively a controlled surface-only boil. With gases the next highest energy state of matter is plasma, a cloud of gaseous ions. But that's ionisation not boiling.

    I suppose if they were talking about a chemical reaction of two gases which produced a visible gaseous product they might've called it 'boiling' in a kind of "it looks like this" way. Or maybe if the reaction produced steam? Either way they've butchered the meaning of the word.
    Thanks so much as always! Now that you give me the confirmation that this process is simply impossible to be true, that makes me feel relieved! It was baffling because I literally couldn't find anything online that suggests an explanation even though I saw many other websites which implied that a gas can boil.

    What you say makes sense now, because thinking about it, they probably meant to talk about the condensation point of a gas rather than the boiling point (because the temperature would still be the same for both).

    So thanks again, much appreciated!
    Offline

    0
    ReputationRep:
    Hey, I'm really struggling with Hess's cycle especially of a reaction.
    I've been doing this question for ages and i still can't get my head around it could anyone help ?

    Question
    Lead forms several solid oxides the most common ones are PbO , PbO2 and Pb3O4.
    Part 1 said write an equation for the formation of PbO
    then Part 2 said, 3PbO+1/2O2= Pb3O4
    enthalpies of formation are:
    PbO=-219
    Pb3O4=-735

    I worked out the standard enthalpy change of the reaction and it came to 78kJmol-1

    but this is is the part I'm confused by ...

    when Pb3O4 is heated it decomposes to PbO and PbO2
    enthalpy change of the reaction is 20kJmol-1
    so now i need to find the enthalpy change of formation of PbO2 from this data
    Offline

    2
    ReputationRep:
    https://e91d34a60c48d35030cf61ddda06...0Chemistry.pdf

    Q19d) iv. - i dont get why we've mutliplied by 10? like i get that the concentration is multiplied by 10 bc we're going from 25cm^3 to 250cm^3 but isnt the original vinegar solution 25cm^3?
    Offline

    9
    ReputationRep:
    (Original post by Trudy9)
    Hey, I'm really struggling with Hess's cycle especially of a reaction.
    I've been doing this question for ages and i still can't get my head around it could anyone help ?

    Question
    Lead forms several solid oxides the most common ones are PbO , PbO2 and Pb3O4.
    Part 1 said write an equation for the formation of PbO
    then Part 2 said, 3PbO+1/2O2= Pb3O4
    enthalpies of formation are:
    PbO=-219
    Pb3O4=-735

    I worked out the standard enthalpy change of the reaction and it came to 78kJmol-1

    but this is is the part I'm confused by ...

    when Pb3O4 is heated it decomposes to PbO and PbO2
    enthalpy change of the reaction is 20kJmol-1
    so now i need to find the enthalpy change of formation of PbO2 from this data
    May I ask are you doing the Edexcel IAL qualification? Because if that's the case, then you really don't need to worry about Unit 1 topics for the Unit 2 exam! Now for your question, I did actually get stuck on that on a previous past paper, however I watched this video explaining the formulation of Hess cycle's really well and if I find it I shall definitely send you the link. However I do suggest that you focus on Unit 2 revision for the time being that is if you are doing the Edexcel IAL.
    Offline

    10
    ReputationRep:
    https://chemrevise.org/revision-guides/
    for amazing notes
    Offline

    1
    ReputationRep:
    Is everyone ready for tomorrow?
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by biochempsy)
    Is everyone ready for tomorrow?
    I think so.. but edexcel will always find a way to make the paper tricky.. What about you?
    Offline

    1
    ReputationRep:
    I think so too, unit 2 is a hard exam and the fact that there are hardly any patterns between exam papers makes it all the more difficult
 
 
 
Poll
Who is your favourite TV detective?

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.