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    (Original post by amphoterism)
    What is the colour of (Cr(H2O)6)2+? And how to get it?
    Blue cus cr2+ ions are blue ??
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    (Original post by Clarinet)
    The reaction was exothermic so if temperature increased, the reaction would shift to the left so solubility would decrease
    The question stated that solubility is defined as the amount of solid ready to dissolve in a solvent ( in this case, water).
    Hence as more MgCl2(s) is being produced, solubility increases.

    Aqa were sly with this one like Q1A
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    (Original post by Clarinet)
    The reaction was exothermic so if temperature increased, the reaction would shift to the left so solubility would decrease
    Oh did no one write it in terms of entropy? I thought solubility increased because I worked it out with the Gibbs free energy
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    (Original post by Lazarus26)
    for percentage purity i got around 94%
    how
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    (Original post by Clarinet)
    The reaction was exothermic so if temperature increased, the reaction would shift to the left so solubility would decrease

    oh but arent dissociation reactions endothermic?
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    (Original post by Guls)
    everything was easy on that paper except that percentage one. can someone quickly explain it to me.
    So you get your 5:2 oxalate to manganate ion ratio by combining half-cell equations.

    Then you divide moles by three because it was a trimolar potassium iron oxalate compound reacting.

    Then you get mass by multiplying by Mr.

    Then you do % purity and get 94.4%.
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    Were we meant to put P and Na or P4O10 and Na2O??

    I didn't realise if it said oxide or element. If so, what were the other answers in this reaction? Like the reaction in water, was that with the oxide or the element. And what was the reaction for the equation with P?
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    mno4- and c2o4^2- are negatively charged so repel and the reaction has a high activation energy. 3 points for 3 marks.
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    (Original post by ravichauhan11)
    anyone put Zn and HCl , blue

    for Cr3+ to Cr2+ ???
    (Original post by badaman)
    Yeah Zn and HCl.
    Cr[H2O]6^2+ is Blue solution.
    I wrote H+ ions not HCl, do I still get the mark?
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    (Original post by Cadherin)
    So you get your 5:2 oxalate to manganate ion ratio by combining half-cell equations.

    Then you divide moles by three because it was a trimolar potassium iron oxalate compound reacting.

    Then you get mass by multiplying by Mr.

    Then you do % purity and get 94.4%.
    Yessss
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    (Original post by zahraaj1)
    oh but arent dissociation reactions endothermic?
    yeah but it was enthalpy of solution i think which is usually exothermic, if u worked it out it was exo for me anyways

    i think it wanted you to talk about equilibrium like it mentioned in the question
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    (Original post by RefusedAccess)
    The question stated that solubility is defined as the amount of solid ready to dissolve in a solvent ( in this case, water).
    Hence as more MgCl2(s) is being produced, solubility increases.

    Aqa were sly with this one like Q1A
    no , eq shifts to the left, so not favoring the dissociation of MgCl2, therefore solubilty decreases. very similar question came up a few years a go
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    (Original post by Cadherin)
    So you get your 5:2 oxalate to manganate ion ratio by combining half-cell equations.

    Then you divide moles by three because it was a trimolar potassium iron oxalate compound reacting.

    Then you get mass by multiplying by Mr.

    Then you do % purity and get 94.4%.
    well done. how did you find the rest of the paper?
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    i think it went well, but i know i lost marks on some parts for sure --- just hoping unit 4 wasnt as terrible as i originally thought and the grade boundaries even out
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    dissocation reactions are endothermic so the forward reaction is endo so the solubility increases when the temp increases as it shifts to the right (the endo reaction) because the solid ionic lattice (magnesium chloride) dissociates into its aqueous ions which increases the solubility. so idk how its a decrease haha
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    What did people say for effect of increasing pressure on emf
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    For the Mno4- titration quesiton, i put the ratio of mn04 to c204 as 1:5 instead of 2:5, would i still get error carried forward marks?????
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    (Original post by Guls)
    mno4- and c2o4^2- are negatively charged so repel and the reaction has a high activation energy. 3 points for 3 marks.
    Could you also get a mark for saying the collision frequency is very very low ?


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    (Original post by 12284)
    I wrote H+ ions not HCl, do I still get the mark?
    I put H+ too but I don't think so because H+ isn't a reagent... So annoying


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    What did people put down for the last question about colorimetry?


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