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    (Original post by Nomes24)
    I agree with this. Increasing the temperature means they would try to decrease it by using an endothermic reaction (vs exothermic which would increase temperature further) and the endothermic reaction produced hydrogen and iodine, so more of the reactant- hydrogen iodide- would be produced.
    Was there any change in yield of the product?
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    (Original post by thomasconnor)
    The reaction to produce hydrogen iodide was exothermic and so increasing the temp would decrease the yield mate
    'Mate' that is exactly what I said.
    Increasing the temp would favour the forward exothermic reaction. Thus reducing the amount of hydrogen iodide produced.
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    (Original post by Ilyas_99)
    sorry yes, i meant exothermic

    Wait the forward reaction was exothermic , im 100% sure.Decrease in temp = more yield of Hydrogen Iodide because forward reaction produces hydrogen iodide.
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    (Original post by Palette)
    Was there any change in yield of the product?
    The yield of the product would go up, the amount of hydrogen iodide would go down, as more would be used to react into hydrogen and iodine.
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    (Original post by Nomes24)
    I agree with this. Increasing the temperature means they would try to decrease it by using an endothermic reaction (vs exothermic which would increase temperature further) and the endothermic reaction produced hydrogen and iodine, so more of the reactant- hydrogen iodide- would be produced.
    Exactly. There's different ways of saying this obviously. Let's just hope we all get credited for our responses.
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    (Original post by MrTechGamer)
    Wait the forward reaction was exothermic , im 100% sure.Decrease in temp = more yield of Hydrogen Iodide because forward reaction produces hydrogen iodide.
    No, the forward reaction was endothermic and produced hydrogen and iodine. Higher temp would produce more hydrogen and iodine. Lower temp would produce more hydrogen iodide.
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    (Original post by Nomes24)
    The yield of the product would go up, the amount of hydrogen iodide would go down, as more would be used to react into hydrogen and iodine.
    Please tell me thatg i'm right , because i'm almost positive that it said the forward reaction to produce hydrogen iodide is exothermic.Must be !
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    (Original post by Nomes24)
    The yield of the product would go up, the amount of hydrogen iodide would go down, as more would be used to react into hydrogen and iodine.
    But didn't you say that more of the hydrogen iodide (the reactant) would be produced? I'm confused, and I'm hoping for low grade boundaries.
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    (Original post by MrTechGamer)
    Please tell me thatg i'm right , because i'm almost positive that it said the forward reaction to produce hydrogen iodide is exothermic.Must be !
    You're right that to produce hydrogen iodide the reaction was exothermic, but this was the back reaction. Don't know if this affects how you wrote your answer..!
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    (Original post by Nomes24)
    You're right that to produce hydrogen iodide the reaction was exothermic, but this was the back reaction. Don't know if this affects how you wrote your answer..!
    Do u think it would be ok to say that at lower temps more yield of Hydrogen Iodide will be produced , because forward = hydrogen iodide ?
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    (Original post by Palette)
    But didn't you say that more of the hydrogen iodide (the reactant) would be produced? I'm confused, and I'm hoping for low grade boundaries.
    Sorry when I reread I realised I'd put produced instead of used up. Basically if the endothermic reaction is favoured to lower the temperature, more hydrogen and iodine are produced as this is the endothermic reaction. If more hydrogen and iodine are produced, the hydrogen iodide would go down as more would be used up as the reactant in the endothermic reaction. Additionally as the endothermic reaction is favoured, the exothermic reaction which produces hydrogen iodide would go slower so less hydrogen iodide would be produced.

    Don't worry about the grade boundaries. I'm sure many people found the equilibrium questions challenging, and there were a lot of them- should be fine.
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    (Original post by MrTechGamer)
    Do u think it would be ok to say that at lower temps more yield of Hydrogen Iodide will be produced , because forward = hydrogen iodide ?
    Yes, most likely.

    [1 mark] - For saying most likely that the yield/amount of Hydrogen iodide (the compound on the left) goes up.
    [2 marks] - For saying that the forward reaction is endothermic, so if more energy is supplied to the reaction, this is encouraged and more products are produced, reducing the amount of hydrogen iodide - converse will probably be accepted as well: The backward reaction is exothermic, so supplying more energy won't encourage it anymore, and will actually reduce yield of hydrogen iodide.
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    (Original post by MrTechGamer)
    Do u think it would be ok to say that at lower temps more yield of Hydrogen Iodide will be produced , because forward = hydrogen iodide ?
    Your theory is correct however the question asked for how increasing the temperature would affect yield of hydrogen iodide, so I'm not sure you whether you would be credited? I'm not an examiner though, sorry... It's only 2 marks so don't worry yourself.
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    (Original post by Turtlebunny)
    Yes, most likely.
    Ok , lol i think i revised too much and mixed up mark scheme answers , some questions i didnt reread which is a bad habit lol , im probaly gonna get a or something though due to annoying mistake i made with the 5 marker ! , not even on spec.
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    (Original post by Nomes24)
    Your theory is correct however the question asked for how increasing the temperature would affect yield of hydrogen iodide, so I'm not sure you whether you would be credited? I'm not an examiner though, sorry... It's only 2 marks so don't worry yourself.
    \
    Okydoke
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    (Original post by Nomes24)
    Sorry when I reread I realised I'd put produced instead of used up. Basically if the endothermic reaction is favoured to lower the temperature, more hydrogen and iodine are produced as this is the endothermic reaction. If more hydrogen and iodine are produced, the hydrogen iodide would go down as more would be used up as the reactant in the endothermic reaction. Additionally as the endothermic reaction is favoured, the exothermic reaction which produces hydrogen iodide would go slower so less hydrogen iodide would be produced.

    Don't worry about the grade boundaries. I'm sure many people found the equilibrium questions challenging, and there were a lot of them- should be fine.
    I must have written 'no', and then contradicted myself by talking about how equilibrium is restored as more of the backwards reaction takes place to counteract increase in temperature. I was probably thinking of the Haber process there.
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    (Original post by MrTechGamer)
    Ok , lol i think i revised too much and mixed up mark scheme answers , some questions i didn't reread which is a bad habit lol , im probably gonna get a or something though due to annoying mistake i made with the 5 marker ! , not even on spec.
    That 5 marker was really nasty. I definitely dropped something like 10-15 marks going by my predictions. Hopefully in B1 and C1, if I revise a bit more, I can pull my UMS up, hopefully to an A*. We'll have to wait and see :/
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    I wonder how examiners actually credit responses for GCSE science...
    Looking at mark schemes they are really picky, but will an examiner award marks if someone uses alternative wording or if it doesn't include a keyword.. Do they credit students based on their understanding, or whether they 'tick the boxes' - especially for the public (June) examinations where papers haven't ever been taken before??
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    (Original post by Palette)
    I must have written 'no', and then contradicted myself by talking about how equilibrium is restored as more of the backwards reaction takes place to counteract increase in temperature. I was probably thinking of the Haber process there.
    Just a genuine mistake, no biggie so don't worry about it!
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    You know what, I'm going to send an email to AQA. See what they say :P Probably will ignore, since I'm a candidate, not a centre :P
 
 
 
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