Hey there! Sign in to join this conversationNew here? Join for free

Edexcel - Chemistry Unit 2 - 4 June 2013 Watch

  • View Poll Results: Which topic(s) are you finding most difficult?
    Shapes of molecules and ions
    11.66%
    Intermediate bonding and bond polarity
    15.95%
    Intermolecular forces
    9.82%
    Redox
    17.79%
    Group 2 & 7
    40.49%
    Kinetics & Equilibria
    14.11%
    Organic Chemistry - Alcohols and Halogenoalkanes
    39.26%
    Mechanisms
    26.38%
    Green Chemistry
    28.83%

    Offline

    0
    ReputationRep:
    Do Jan 2010 question # 19 c)i). You will get it.
    • Thread Starter
    Offline

    14
    ReputationRep:
    (Original post by airheadbuster)
    Not soluble in water. Soluble in only alcoholic solution.
    Ah yes, since it's a hydrocarbon ? So hydrocarbons only dissolve in other hydrocarbons...

    Thanks
    • PS Reviewer
    Offline

    20
    ReputationRep:
    PS Reviewer
    (Original post by posthumus)
    Ah yes, since it's a hydrocarbon ? So hydrocarbons only dissolve in other hydrocarbons...

    Thanks
    :yep:

    'like for like'.

    Crude oil is a mixture of hydrocarbons and yet they all dissolve with each other!
    Offline

    1
    ReputationRep:
    This thread, youtube and my trusty blue As student book for chem and 7 past papers have taught me everything I need to know for the exam tomorrow all within 10 days Can't wait to do the exam now
    Offline

    0
    ReputationRep:
    Why is iodine such a strong reducing agent?
    Offline

    2
    ReputationRep:
    how many raw marks can you usually lose and still get an A?
    Offline

    0
    ReputationRep:
    (Original post by kevsamuel)
    Why is iodine such a strong reducing agent?
    Iodine is not a reducing agent. Iodide ion is. My question exactly. Where is Mister Good?
    Offline

    0
    ReputationRep:
    Please i just joined the thread and im finding it hard to get the predictions what are e generel predictions for the exam
    Offline

    0
    ReputationRep:
    (Original post by Kurraiyo)
    how many raw marks can you usually lose and still get an A?
    Consider 18 an average.
    Offline

    0
    ReputationRep:
    (Original post by Goods)
    tertiary carbocations aren't more stable. tertiary carbocations are a more stable intermediate. tertiary haloalkanes are the most reactive because the carbocation is more stable (more +ve) easy for leaving group to leave
    Could someone please explain what this guy means?
    Offline

    14
    ReputationRep:
    it's really challenging to score 20 in section A .. I usually score about 18 marks in this section
    Offline

    16
    ReputationRep:
    (Original post by airheadbuster)
    I thought the reactivity was determined in terms of intermolecular force strength and ya, tertiary carbocations are a more stable intermediate.
    Could you please explain a bit more?
    Surrounding alkyl groups push electron density away from themselves this makes the carbocation less positive and more stable. However the halogen is slightly negative and so being a less positive carbocation due to surrounding bulky groups the halogen carbon bond is weaker. The type of halogen also effects the bond strength depending on its radius. The reactivity is dependent on the activation energy therefore the strength of the bonds is the major issue when considering reactions.


    Posted from TSR Mobile
    Offline

    2
    ReputationRep:
    (Original post by kevsamuel)
    Why is iodine such a strong reducing agent?
    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
    Offline

    16
    ReputationRep:
    (Original post by posthumus)
    Nope, it gets weaker ! I'm talking about intramolecular forces by the way not intermolecular


    Also does anyone know if all halogenoalkanes are soluble ???
    All amines are right ??? dude to hydrogen bonding
    Short chain haloalkanes are but normally ethanol is added to dissolve the haloalkanes so the they can miss with aqueous solutions


    Posted from TSR Mobile
    Offline

    0
    ReputationRep:
    (Original post by Goods)
    Surrounding alkyl groups push electron density away from themselves this makes the carbocation less positive and more stable. However the halogen is slightly negative and so being a less positive carbocation due to surrounding bulky groups the halogen carbon bond is weaker. The type of halogen also effects the bond strength depending on its radius. The reactivity is dependent on the activation energy therefore the strength of the bonds is the major issue when considering reactions.


    Posted from TSR Mobile
    I meant why are tertiary halogenoalkanes more reactive? Could you please point me to the source of your information?
    Offline

    0
    ReputationRep:
    (Original post by Goods)
    Short chain haloalkanes are but normally ethanol is added to dissolve the haloalkanes so the they can miss with aqueous solutions


    Posted from TSR Mobile
    Where did you find short halogenoalkanes are soluble in water?
    Offline

    16
    ReputationRep:
    (Original post by airheadbuster)
    Where did you find short halogenoalkanes are soluble in water?
    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


    Posted from TSR Mobile
    • Thread Starter
    Offline

    14
    ReputationRep:
    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?
    Offline

    2
    ReputationRep:
    (Original post by Jayqwe)
    This thread, youtube and my trusty blue As student book for chem and 7 past papers have taught me everything I need to know for the exam tomorrow all within 10 days Can't wait to do the exam now
    YouTube? Any channels in particular?


    Posted from the TSR iPad app
    Offline

    16
    ReputationRep:
    (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?
    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



    Posted from TSR Mobile
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Brussels sprouts
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Quick reply
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.