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Edexcel - Chemistry Unit 2 - 4 June 2013 Watch

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    (Original post by Kurraiyo)
    Iodide is the strongest reducing agent because, due to its largest radius, it has the lowest charge density. So the nuclear pull on the extra electron in the iodide ion is weakest, and thus it is easiest to remove. With chloride, for example, the charge density of the chloride ion is much higher and so the extra electron is held more tightly. So it is not easy to oxidise a chloride ion (in other words it is a weak reducing agent). Hope that helps
    Thank you soo much!
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    (Original post by Goods)
    Yep
    In jan 2011 do you know the question about what happens when a tube of HI is inverted in water? The mark scheme isn't clear and I don't know the answer



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    It dissolves in the water, all hydrogen halides are soluble in water
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    (Original post by posthumus)
    So what's the test for HCl (I saw that blue litmus turning red was no accepted in a past paper ).

    Add NH3 ... to form NH4Cl?? Observe white solid/smoke?
    HBR also forms white solid with ammonia. Most likely the test it to add HNO3 followed by silver nitrate solution. A white precipitate of AgCl will form which dissolves in dilute ammonia, forming [Ag(NH3)]+

    (Not sure though. What does the mark scheme say?)
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    (Original post by Goods)
    Yep
    In jan 2011 do you know the question about what happens when a tube of HI is inverted in water? The mark scheme isn't clear and I don't know the answer



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    HI gas is soluble in water. So, the water will rise up the inverted tube.
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    (Original post by Goods)
    My brother said it when I was complaining about a mark scheme he studies chem at uni it's not worth worrying over they won't ask about it in that way. The stuff about carbocations is also extra syllabus it's just nice to apply the kinetics to see why trends occur. For the exam you need to know that haloalkanes react faster if the halogen atom is further down the group and that the tertiary carbocation is more stable than a primary carbocation due to having surrounding alkyl groups. sorry if I was stressing you making you think you didn't know something critical


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    I know all that. I just don't get how tertiary halogenoalkanes are more reactive than primary halogenoalkanes. It's bugging me .
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    (Original post by airheadbuster)
    I know all that. I just don't get how tertiary halogenoalkanes are more reactive than primary halogenoalkanes. It's bugging me .
    They are more reactive because the carbon attached to the halide has more CH3 groups attached to it. A CH3 group tends to push electrons in the bond away from itself; and encourages the release of the halide.
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    (Original post by scientific222)
    They are more reactive because the carbon attached to the halide has more CH3 groups attached to it. A CH3 group tends to push electrons in the bond away from itself; and encourages the release of the halide.
    I get it now. :thumbsup:

    Edit: :sleepy: Best of luck guys.
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    this might help you guys revise.

    Edexcel AS Chemistry Unit 2.pdf
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    I'm happy about my knowledge until I come to this thread and all the people's discussions confuse me. xD
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    Name:  image.jpg
Views: 133
Size:  515.4 KB Can someone answer the q with the star please
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    (Original post by thextractor007)
    this might help you guys revise.

    Edexcel AS Chemistry Unit 2.pdf


    Thank you so much just what I was looking for , best of luck !
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    (Original post by Lillian Collins)
    Thank you so much just what I was looking for , best of luck !
    You too. My pleasure. This is a summary so just go through it before the exam.

    Chemistry Summary Unit 2.pptx
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    This how I d answer it, not saying I'm right i just hope i am...
    Answer:C- because all the group 2 metals react with chlorine to form ionic salts (solids) [except for beryllium chloride which is covalent but that's solid too anyway]
    Why these are not right:
    A- Metal oxides neutralise dilute acid- so an alkaline pH like 10 would make sense (not that I knew the pH was 10)
    B- Group II sulfates follow the same solubility trends as carbonates though I'm pretty sure that's not in our spec?
    D- Group I metal carbonates except Lithium do not compose but group II do
    Hope that's right otherwise I should probably just give up x
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    (Original post by Lillian Collins)
    Name:  image.jpg
Views: 133
Size:  515.4 KB Can someone answer the q with the star please
    It is C. The group 2 metals burn in chloride to form solid metal chlorides
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    (Original post by thextractor007)
    You too. My pleasure. This is a summary so just go through it before the exam.

    Chemistry Summary Unit 2.pptx
    Wow dude thanks!
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    can someone please please please list me all of the trends in the periodic table we need to know? I'm a bit lost on this, thank you!
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    (Original post by Tuya)
    YouTube? Any channels in particular?


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    There is Khan's academy, chemistNATE and mr causey which are the main three I used
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    (Original post by Maybenexttime)
    I'm happy about my knowledge until I come to this thread and all the people's discussions confuse me. xD
    i feel u bro
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    (Original post by thextractor007)
    You too. My pleasure. This is a summary so just go through it before the exam.

    Chemistry Summary Unit 2.pptx
    Just perfect , thank you !
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    Do we need to know any drying agents? And do we need to no how to separate ethanol from water
 
 
 
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