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    (Original post by posthumus)
    Ah yes, I see... Lattice enthalpy is less negative with the small OH- anion... therefore less positive -Hlatt ..... So therefore enthalpy of hydration is able to "keep up" and outweigh it!

    This whole time I thought lattice enthalpy was positive as energy is needed to break a lattice. But this probably goes back to the fact that all bond breaking is exothermic... which I don't think I ever will understand in my life
    LOL! you sure didnt coz bond MAKING is exo BREAKING is endo
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    (Original post by AS01)
    LOL! you sure didnt coz bond MAKING is exo BREAKING is endo
    :O I meant bond making I understand breaking requires energy... but I thought to make a bond you also require energy.

    but anyway, back to this lattice enthalpy stuff... you need energy to break the lattice... but when you break it, it produces more energy! (I never even thought about that last bit)
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    (Original post by posthumus)
    :O I meant bond making I understand breaking requires energy... but I thought to make a bond you also require energy.

    but anyway, back to this lattice enthalpy stuff... you need energy to break the lattice... but when you break it, it produces more energy! (I never even thought about that last bit)
    http://www.thestudentroom.co.uk/showthread.php?t=371500

    wait! wait! you need energy to break lattice and this energy needed will then be overcomed by energy released in forming bond with the solvent ions. lol if it produces more energy then conservation of energy law will be violated
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    everybody ready for thiS??? Good Luck to u all
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    (Original post by AS01)
    http://www.thestudentroom.co.uk/showthread.php?t=371500

    wait! wait! you need energy to break lattice and this energy needed will then be overcomed by energy released in forming bond with the solvent ions. lol if it produces more energy then conservation of energy law will be violated
    #No but when it forms bonds with solvents thats hydration enthalpy

    Lattice enthalpy is when you break it into 1 mole of gas.... so where is the energy compensated :confused: Is the energy in the ionic bonds just released as heat ?


    Also AS01 do you remember Q3 on Jan 2013 Where it was an overall first order reaction... pressure was halved but there was no change in half-life. Why exactly ? This has been confusing me all day

    Also thanks for the link
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    (Original post by AS01)
    yay! one is here
    you don't coz the vertical section of graph is rarely even there.

    give an example of addition elimination reaction of acyl chloride.

    hmm...? u mean there is no indicator at all for weak acid/ weak base?? :confused:
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    (Original post by posthumus)
    #No but when it forms bonds with solvents thats hydration enthalpy

    Lattice enthalpy is when you break it into 1 mole of gas.... so where is the energy compensated :confused: Is the energy in the ionic bonds just released as heat ?


    Also AS01 do you remember Q3 on Jan 2013 Where it was an overall first order reaction... pressure was halved but there was no change in half-life. Why exactly ? This has been confusing me all day

    Also thanks for the link
    lattice energy is when u break ionic compound and get gaseous ions. Energy put in?
    its coz yeah u can link order of reaction even with pressure its not always conc. so when pressure was halved the half life stayed same
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    (Original post by Amila888)
    hmm...? u mean there is no indicator at all for weak acid/ weak base?? :confused:
    yup! there are indicators but it wont change color when u titrate weak acid with weak base coz for this the vertical section of graph is small hardly like 2 units. For indicators to change colour their range must lie in verticals section since we hardly even have the vertical section it wont even change color.
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    (Original post by Amila888)
    everybody ready for thiS??? Good Luck to u all
    I finished revising and all. So all depends on paper now
    what about you?
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    (Original post by AS01)
    lattice energy is when u break ionic compound and get gaseous ions. Energy put in?
    its coz yeah u can link order of reaction even with pressure its not always conc. so when pressure was halved the half life stayed same
    Okay thank you So first order reactions half-lifes are only changed by temperature?

    Where as second order reactions... what would have happened to the half-life if the pressure was halved ?

    And is catalyst ever included in rate equation & does pressure effect equilibrium constant (Sorry I have too many question to ask )

    Also I think I have a good equilibria question here from the Jim Clark book I can't do it anymore I was so much more prepared in Jan...

    "An excess of finely divided tin and lead was shaken with a solution containing 1.0 moldm^-3 of lead(II) ions and 0.5 moldm^-3 of tin(II)ions. Calculate the equilibrium concentrations of lead(II) and tin(II) ions:

    Sn(s) + Pb^2+ <-----> Pb(s) + Sn^2+

    Kc=2.2

    Also to do with Kp I keep thinking ions also exert a pressure, therefore are included in the Kp expression :confused:
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    (Original post by AS01)
    I finished revising and all. So all depends on paper now
    what about you?
    yup.. me finished too waiting till the game starts... by the way, u did the sample paper by edexcel ? its pretty damn hard.
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    (Original post by Amila888)
    yup.. me finished too waiting till the game starts... by the way, u did the sample paper by edexcel ? its pretty damn hard.
    no I havent lol
    wait lemme give it a try
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    sample paper : http://www.ashlyns.herts.sch.uk/down...arkschemes.pdf

    if u got a minute, u cud check through it.. its 2007.. cudnt find a more recent one.. i found the last few questions hard...
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    (Original post by posthumus)
    Okay thank you So first order reactions half-lifes are only changed by temperature?

    Where as second order reactions... what would have happened to the half-life if the pressure was halved ?

    And is catalyst ever included in rate equation & does pressure effect equilibrium constant (Sorry I have too many question to ask )

    Also I think I have a good equilibria question here from the Jim Clark book I can't do it anymore I was so much more prepared in Jan...

    "An excess of finely divided tin and lead was shaken with a solution containing 1.0 moldm^-3 of lead(II) ions and 0.5 moldm^-3 of tin(II)ions. Calculate the equilibrium concentrations of lead(II) and tin(II) ions:

    Sn(s) + Pb^2+ <-----> Pb(s) + Sn^2+

    Kc=2.2

    Also to do with Kp I keep thinking ions also exert a pressure, therefore are included in the Kp expression :confused:
    no it doesnt change at all. remember in first order successive half life is always constant? and in second it differs so cant tell
    No for both of them
    lol u forgot to give me equation but found it on book
    Pb-0.47 Sn-1.03
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    (Original post by Amila888)
    sample paper : http://www.ashlyns.herts.sch.uk/down...arkschemes.pdf

    if u got a minute, u cud check through it.. its 2007.. cudnt find a more recent one.. i found the last few questions hard...
    thank you!
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    (Original post by AS01)
    no it doesnt change at all. remember in first order successive half life is always constant? and in second it differs so cant tell
    No for both of them
    lol u forgot to give me equation but found it on book
    Pb-0.47 Sn-1.03
    For second order can we calculate how much it differs by ? Or should I not worry about this
    & people have been telling me different things on here lol It's always temperature isn't it effecting everything!

    Sorry I thought I did .. but how'd you work that out ?! :eek:

    Thanks
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    (Original post by posthumus)
    For second order can we calculate how much it differs by ? Or should I not worry about this
    & people have been telling me different things on here lol It's always temperature isn't it effecting everything!

    Sorry I thought I did .. but how'd you work that out ?! :eek:

    Thanks
    you should not worry about that
    Only temperature affect Kc and the only thing u include in Kc is what is given in question
    lol i dont know what to say. umm u include ions, gas even but no never catalysts.
    Pb2+= 1-x
    Sn2+= 0.5+x
    now just use Kc=Pb2+/Sn2+ to find x
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    (Original post by AS01)
    you should not worry about that
    Only temperature affect Kc and the only thing u include in Kc is what is given in question
    lol i dont know what to say. umm u include ions, gas even but no never catalysts.
    Pb2+= 1-x
    Sn2+= 0.5+x
    now just use Kc=Pb2+/Sn2+ to find x
    Thank-you I think I should just chill out a bit now, I am panicking too much I need an A in this specific exam
    It's annoying that its in the afternoon ! Because I have C3 & Physics next day, too little time to prepare for those ! :mad:
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    (Original post by posthumus)
    Thank-you I think I should just chill out a bit now, I am panicking too much I need an A in this specific exam
    It's annoying that its in the afternoon ! Because I have C3 & Physics next day, too little time to prepare for those ! :mad:
    I have physics as well!!!
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    (Original post by AS01)
    I have physics as well!!!
    I got A already in unit 4 physics, but because of my stupid ISA practical marks I have to retake it !!

    Do you have anything else to learn for this unit? Still haven't learnt all enthalpy definitions either - do you feel more or less prepared than January ?
 
 
 
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