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    for exothermic its always products - reactants doofuses .. its combustion ... how can u burn sumthing as a fuel and get a positive delta H .... !!!

    it was def - 891 ...
    the next part of the question was a give away ... all u had to say was tht the significance of the negative sign means tht heat is lost to the surroundings
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    it was definitely exothermic
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    (Original post by Heidi)
    it was definitely exothermic
    what did u rite for the next part ... ? .. i rote tht methane is almost ideal becuase of its low cost and the fact tht u get more energy per gram burnt .. but u need sophisticated equipment like pressurized tanks and pipes to use it effiiciently as compared to the liquid whihc can easily be stored in a barrel or sumthing
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    did u have to recommend one? i thought they just wanted advantages and disadvantages
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    i saw there were like 6 or 7 marks for the damn thing ... so i actually calculated the whole thing and showed tht u get more energy per gram for methane ... nice way to fill up a few lines 8-)
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    (Original post by ram)
    did u have to recommend one? i thought they just wanted advantages and disadvantages
    XDDD~~~~
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    it was only 3 marks on my paper....
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    ok i mite be confused... was the question after the enthalpy of combustion one (what is the significance of the sign blah blah ) ... and then the one after tht was to determine which was a better fuel ....
    i cant remember if they were in the same paper
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    (Original post by ram)
    it was only 3 marks on my paper....
    duh
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    (Original post by z!D4N)
    duh

    does that mean it was 3 marks?

    also u didnt hv to recommend a fuel, i just checked with a friend.
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    Just a question re this paper, if a question asks for reagent and its only worth one mark is heat/reflux a must for the mark?

    Was just thinking of the exam and realised I didnt mention boiling under reflux at all. Think I've majorly messed up.
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    (Original post by ƒlå®è®)
    I had -891 Which i think is correct, but im not too sure
    Yes I got the same answer!
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    (Original post by ram)
    does that mean it was 3 marks?

    also u didnt hv to recommend a fuel, i just checked with a friend.
    Yes I am sure

    According to the past paper, what you need to answer are the three adv/disadv with reference to the three rows in the table
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    (Original post by keisiuho)
    Yes I got the same answer!
    so did i -891
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    yes -89x... 8)
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    (Original post by kpg)
    Just a question re this paper, if a question asks for reagent and its only worth one mark is heat/reflux a must for the mark?

    Was just thinking of the exam and realised I didnt mention boiling under reflux at all. Think I've majorly messed up.
    no
    heat/reflux is an answer to reaction conditions
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    sorry it was a typo error
    i put an exothermic reaction...but there is a negative sign there
    you do not need to write the hess law cycle down since it is not asked
    but you can...

    and yeah,the data i used was not accurate cause i cant remember what they used but i do know the answer was -891kJmol-1
    this is i am pretty certain cause i asked like 8 people and they all got the same thing

    kpg : when they asked for reagents,you should only write reagents but not conditions (heat under reflux).However there was a question at where you were asked to name the process of nuclephilic substitution and elimination
    the condition was boiling under reflux with the prescence of ethanol for the elimination reaction..therefore the condition had a reagent..thats why there was 3 points there
    1 for clasifying the reaction and 2 for writing the 2 conditions
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    (Original post by MalaysianDude)
    sorry it was a typo error
    i put an exothermic reaction...but there is a negative sign there
    you do not need to write the hess law cycle down since it is not asked
    but you can...

    and yeah,the data i used was not accurate cause i cant remember what they used but i do know the answer was -891kJmol-1
    this is i am pretty certain cause i asked like 8 people and they all got the same thing

    kpg : when they asked for reagents,you should only write reagents but not conditions (heat under reflux).However there was a question at where you were asked to name the process of nuclephilic substitution and elimination
    the condition was boiling under reflux with the prescence of ethanol for the elimination reaction..therefore the condition had a reagent..thats why there was 3 points there
    1 for clasifying the reaction and 2 for writing the 2 conditions
    I am quite confused with the use of heating, reflux and boiling.
    What factors determine whether reflux or boiling is required?
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    boiling is with addition of water
    heating is without
    some need to be dissolved some doesnt...
    but anyways,if you did put heat under reflux,id think its gonna be correct as well
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    (Original post by MalaysianDude)
    boiling is with addition of water
    heating is without
    some need to be dissolved some doesnt...
    but anyways,if you did put heat under reflux,id think its gonna be correct as well
    ......
    I put heat only.......
 
 
 
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