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OCR B (Salters) F332 Tuesday 4th June 2013 Exam Discussion (Now Closed) watch

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    (Original post by krisshP)
    Say if they say ozone problems in troposphere?
    Ow we say respiratory diseases or respiratory problems or breathing difficulties or what? They are really annoying with their mark schemes.
    In the revision guide it says "breathing problems" but I don't remember exactly what it says in the mark scheme, I'll double check for you. You can always say other things too like, its an irritant toxic gas, and it weakens the immune system etc.
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    thank you love
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    i really need help with reactions of alcohols. what are the reactants, products, conditions and reagants for them?
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    Need some advice: Should I do chem past papers now or later? I haven't really reviewed my notes so I was wondering if it was better to read my notes and then do past papers (I keep doing bad in the past papers)
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    (Original post by wolfie_)
    i really need help with reactions of alcohols. what are the reactants, products, conditions and reagants for them?
    Oxidation of primary alcohols:
    • Aldehyde: distil in situ, acidified potassium dichromate (VI), solution goes from orange to green, if this is further oxidised then you get carboxylic acid.
    • Carboxylic acid: heat under reflux with excess acidified potassium dichromate (VI), colour change from: orange to green

    Oxidation of secondary alcohols:
    • Ketone: acidified potassium dichromate (VI), colour change from: orange to green

    Oxidation of tertiary alcohols:
    • doesn't oxidise, colour change from: orange to orange


    Dehydration of alcohol (elimination reaction): gives you an alkene
    • In lab: heat under reflux, with concentrated sulfuric acid
    • In industry: Aluminium oxide, 300oC at 1atm.


    Formation of halogenoalkane: nucleophilic substitution
    • Bromoalkane: HBr (aq) + NaBr (s) + conc. sulfuric acid
    • Chloroalkane: conc. hydrochloric acid at room temp + pressure
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    (Original post by Whostolemycookie)
    Need some advice: Should I do chem past papers now or later? I haven't really reviewed my notes so I was wondering if it was better to read my notes and then do past papers (I keep doing bad in the past papers)
    How many past papers have you done so far? And what are you averaging?
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    (Original post by nukethemaly)
    How many past papers have you done so far? And what are you averaging?
    D/Es I've done like 4 past papers but I've done way more in the past
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    (Original post by Whostolemycookie)
    Need some advice: Should I do chem past papers now or later? I haven't really reviewed my notes so I was wondering if it was better to read my notes and then do past papers (I keep doing bad in the past papers)
    I usually do the past papers and learn content from answering the questions. If some of the content isnt covered then I use the book aftwerwards
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    (Original post by Whostolemycookie)
    D/Es I've done like 4 past papers but I've done way more in the past
    I would suggest doing past papers then, and then referring back to the book for topics you keep losing marks on
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    (Original post by nukethemaly)
    I would suggest doing past papers then, and then referring back to the book for topics you keep losing marks on
    Ok thanks
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    (Original post by SyedaK)
    I usually do the past papers and learn content from answering the questions. If some of the content isnt covered then I use the book aftwerwards
    Another question, when doing past papers do you analyses the advance notice it comes with?
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    This is from January 2001 paper please help!
    Quick question:
    "Solutions of sodium hypochlorite in water can react with organic matter to form trace amounts of compounds which are suspected carcinogens. One such compound is chloromethane, CH3CL. In the UK, the government has set a limit of 1.0 times ten to the minus 4 ppm (standard form thing) by mass for chloromethane in drinking water.

    What is the maximum mass of chloromethane allowed in 1000g of drinking water?"
    I don't get this question at all :/

    But if it helps, the answer is 1 times ten to the minus 7 (standard form), so 0.0000001
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    (Original post by ngullan)
    Does anyone have the paper from january 2013?

    Also, any ideas on how I can fully understand electrophilic/nucleophilic addition? I've spent loads of time on it, and I think I understand how they differ, but I always lose marks for the reaction mechanisms.
    Think about this way in A-level standard: for most of the time they require an electrophilic addition reaction, they usually give you a C=C bond as a clue.
    Why?
    This is because an electrophile attacks a region of high electron density (a C=C bond has high electron density). This means the chemical species acting as an electrophile with a slight/full positive charge will be attracted to this high electron density and react by accepting a lone pair of electrons to form a new covalent bond.

    A nucleophile will be slightly/fully negative which has a lone pair of electrons and will donate them to form a new (dative) covalent bond.

    Differences:
    Electrophile - has a slight/full positive charge, reacts by accepting a lone pair of electrons. Almost always occurs with a C=C bond. Arrow moves from C=C bond to electrophile.
    Nucleophile -hasa slight/full negative charge that attracts a slightly positive Carbon atom, reacts by donatinga lone pair of electrons to form a new dative covalent bond, arrow moves from nucleophile to molecule/compound
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    (Original post by krisshP)
    Wouldn't you run out of time in n exam by putting both?
    Hardly, they're three extra words and you do get quite a fair amount of time in the exam!
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    (Original post by carla6600)
    This is from January 2001 paper please help!
    Quick question:
    "Solutions of sodium hypochlorite in water can react with organic matter to form trace amounts of compounds which are suspected carcinogens. One such compound is chloromethane, CH3CL. In the UK, the government has set a limit of 1.0 times ten to the minus 4 ppm (standard form thing) by mass for chloromethane in drinking water.

    What is the maximum mass of chloromethane allowed in 1000g of drinking water?"
    I don't get this question at all :/

    But if it helps, the answer is 1 times ten to the minus 7 (standard form), so 0.0000001
    I remember doing this question and I still dont get it. I've emailed my teacher about it and when she replies I'll let you know!
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    Why the formula of calcium chlorate(I) is Ca(ClO2)?
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    How do bond strength and polarity differ, doesnt polarity play a part in bond strength?

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    (Original post by michmic)
    Why the formula of calcium chlorate(I) is Ca(ClO2)?
    Isn't that Calcium Chlorate(III) ?

    Posted from TSR Mobile
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    (Original post by nukethemaly)
    I remember doing this question and I still dont get it. I've emailed my teacher about it and when she replies I'll let you know!
    Thank you!!
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    Quick Question

    Calculate the % of avaliable chlorine in chlorine dioxide when it is reduced to chloride

    you do 35.5/35.5+2*16 * 100 then * 5
    why do you have to times it by 5 =/
 
 
 
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