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    Did anyone get ph 3.55 for the buffer question?


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    (Original post by jirapat121)
    What did you guys get for the enthalpy change question?
    -1099
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    (Original post by Vannzzoo)
    -1099
    yess!!!!! sameeee
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    in the buffer was it just ka x 0.04/0.05
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    (Original post by Vannzzoo)
    -1099
    I got +1000 something… shouldn't it be endothermic since bonds are breaking?
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    What did you put for the written bit about equilibrium with iodine? 'Why isn't it soluble and observations' and what did you put on the redox qu with Cr3+? Also what was the method for the buffer question? I can't remember my answer but I want to reassure myself that my method was right. And did anyone get 104 for Kc? Seemed a large vakue
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    (Original post by comeonengland1)
    in the buffer was it just ka x 0.04/0.05
    Agreed, 3.43

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    (Original post by ArthurDayne)
    Answer dump:
    Q3: -1099 DHhyd
    -43.05
    Q4 104 Kc dm3mol-1
    Q5 ph 2.12
    3.43 ph buffer
    13.03
    ph naoh dilute 10.76

    x=4
    Everything correct, well done

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    (Original post by ArthurDayne)
    Answer dump:
    Q3: -1099 DHhyd
    -43.05
    Q4 104 Kc dm3mol-1
    Q5 ph 2.12
    3.43 ph buffer
    13.03
    ph naoh dilute 10.76

    x=4
    Concur though i am wondering if i had 10.77.
    I don't recall. Chemistry answers are difficult to remember.
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    That iodine question messed me up, anyone know why I2 isn't soluble and what happens when u add silver nitrate?
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    Good paper loved it

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    (Original post by HFancy1997)
    Everything correct, well done

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    got exactly the same so happy
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    (Original post by HFancy1997)
    Agreed, 3.43
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    ka x 0.04/0.05.... lol awwkward when u forgot to square it R.I.P becoming a chemist..... 10/10 get rekt
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    On the buffer question you were given the concentration of HNO2 (weak acid) and the conc of NaNO2 (conjugate base) surely you could just put those concentrations into the Ka expression. Why did everyone use the moles?
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    (Original post by maisym00)
    What did you put for the written bit about equilibrium with iodine? 'Why isn't it soluble and observations' and what did you put on the redox qu with Cr3+? Also what was the method for the buffer question? I can't remember my answer but I want to reassure myself that my method was right. And did anyone get 104 for Kc? Seemed a large vakue
    I blagged something about the H2O not inducing a dipole in the I-I bond.
    The buffer was HNO2 > H+ + NO2- I think
    So added H+ moves the position of eqm to the left to remove the excess H+ from solution and form more HNO2
    Added OH- reacts with the H+ to form water and the position of eqm moves to the right to restore the H+ ions

    I don't think I got the same value as you for Kc. I can't remember what I did get but it wasn't as high as 100.
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    (Original post by Kvothe the arcane)
    Concur though i am wondering if i had 10.77.
    I don't recall. Chemistry answers are difficult to remember.
    I think I got 11.something but not sure
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    Does anyone have a qs/mark breakdown? Or planning to make one?
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    (Original post by maisym00)
    On the buffer question you were given the concentration of HNO2 (weak acid) and the conc of NaNO2 (conjugate base) surely you could just put those concentrations into the Ka expression. Why did everyone use the moles?
    Because it was W amount of X moldm-3 and Y amount of Z moldm-3 so their concentrations in the overall solution are lower. You had to work out the number of moles so that you knew their concentration in the full volume of solution.
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    (Original post by Ohhhhhh)
    That iodine question messed me up, anyone know why I2 isn't soluble and what happens when u add silver nitrate?
    i said I2 is non polar so it won attract the water molecule due to no dipoles .. don't know if its right tbh
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    (Original post by Kingofcastle01)
    I got +1000 something… shouldn't it be endothermic since bonds are breaking?
    Hydration is alwayd exothermic

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