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OCR Chemistry F322~ 4th June 2013~ AS Chemistry Watch

  • View Poll Results: How did you find the exam
    Hard A= 72
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    It was okay A= 76
    99
    35.87%
    Easy A= 79
    75
    27.17%
    Very Easy A=82
    60
    21.74%

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    (Original post by NataliaWojcicka)
    You know where it had the energy profile diagram drawn, and it asked for enthalpy change when 240 dm^3 is formed, did you have to times by 5 or 10?

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    Times by 5, because the equation given forms 2 moles of N2O.
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    i messed up on the radical stuff,i said radical substitution,said homolytic fission,said propagation and initiation,gave the intiantion equation but couldnt for the life of me do the two equations so is that like 5/7 or 4/7? marks
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    Was I the only one that didnt come out of that feeling confident? I didnt find it difficult as such, but what the questions where trying to get at sometimes was not obvious, did anyone else feel that??
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    guys wheres the UNOFFICIAL MARK SCHEME? is there one yet? I think the grade boundaries should be lower than the jan 2013 paper,,,i found this paper a lot harder than jan 2013....
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    Here it comes
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    This is what I did for the first 2 Q's A* posted feel free to correct.

    Q1.
    a) i) C10H22
    ii) 2-methylnonane
    iii) Fewer points of contact, less VDWs, less energy required to break them.

    b) i) C15H32  C10H22 + C5H10
    ii) Carbon to carbon bond can be broken in a variety of places.

    c) i) Draw an octagon
    ii) Cyclic hydrocarbons burn more efficiently as fuels

    Q2.
    a) i) E & H
    ii) H
    iii) F

    b) i) C5H9OH
    ii) 2-methylpentan-3-ol

    c) A series of organic compounds with the same functional group, each differing by CH2.

    d) 1st box -> Ketone, same as diagram but change –OH to =O

    2nd box -> Ester, same as diagram minus the H on –OH, add ethanoic acid but minus H on the carboxyl.

    4th & 3rd box -> Alkene, same as diagram minus –OH and put a double bond in the ring. H20 in other box due to dehydration.
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    (Original post by 344302)
    Oh good! I was doubting myself for a minute !!

    Hey you know the equilibrium question? Did you put left and left or left and right or what.

    I can't even remember . I think I counted the moles wrong for the pressure. Damn


    Posted from TSR Mobile
    I got left and left, but I think temperature was right, not to sure.
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    (Original post by Gotzz)
    By 5
    Omg.... I did that and then I thought it says per mole by the number, so it should be by 10... And I changed it....

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    (Original post by chigyy)
    Was the colour change orange to green or colourless?
    orange to colourless. it said somethnig about bromine so
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    You know the 4 marker of the boxes, yes I know it said organic producst, but obviously h20 is formed so i feel they may accept that.....
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    (Original post by Sally_Riley)
    Was I the only one that didnt come out of that feeling confident? I didnt find it difficult as such, but what the questions where trying to get at sometimes was not obvious, did anyone else feel that??
    me too dw usaully people do okay who found it challanging i found it toughish but just dragging ...hard to explain?
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    (Original post by NataliaWojcicka)
    Omg.... I did that and then I thought it says per mole by the number, so it should be by 10... And I changed it....

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    The original equation formed two moles, 2x5=10
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    (Original post by cyiarik)
    A SORT OF UNNOFFICIAL MARK-SChEME (MAY BE OUT OF ORDER)

    First Question
    -
    C10H22
    - (drawn) any branched isomer of c10h22 AND named [ i put 2-methylnonane ]
    - (cracking question) C15H31 ----> C10H20 + C5H12 (any suitable equation-
    - why does cracking hydrocarbons produce many products? C-C bond can break anywhere in the hydrocarbon chain
    - (drawn) cyclo-octane i drew both skeletal and displayed formula of this just in case
    - cyclo-alkanes are made because they burn more efficiently/ have a higher octane rating

    Other question answers :
    - homologous series: molecules that have same functional group but each successive member differs by a CH2
    - burns with black smoke due to imcomplete combustion/ black smoke and yellow flame indicates there was a lack of oxygen therefore it did not combust completely.
    - [question about why does something have 100% atom economy] because there was only 1 product produced in the reaction/ no waste products were produced in the reaction

    Question about weird looking molecule thing showing E/z isomerism:
    - functional groups present were an ester and an alkene (c-c double bond and a c-o double bond o)
    - structure j is different from structure i because in I both the groups are on the same side of the double bond (Z isomerism) whereas in J each group is on the different sides of the c-c double bond (E isomerism)
    Box Drawings for products of Alcohol when
    1-oxidised
    2-reacted with a carboxylic acid
    3-dehydrated/hydrated

    • 1st box was and ester or an aldehyde (may have to draw both)
    • 2nd box was an ester + H20
    • 3rd and 4th boxed were dehydration/hydration

    For the question about halogenoalkanes:
    - most unreactive: i put the first one (N)
    - Most reactive one had 2 halogens in it (I and Br)

    - P had a lower b/p than Q because P contained Br and Q contained I. The C-I bond is longer than the C-Br bond, thus it is easier to overcome the C-I bond as it experiences less attraction to the nucleus of the C atom/ takes less energy to overcome C-I bond.

    Had to choose one of the halogenoalkanes to demonstrate electrophilic addition (1) + diagram

    For the Le chatelier question:
    increasing temp: favours reverse reaction/position shifts to reduce temp, backward reaction endothermic
    Increasing pressure: favors forward reaction, position of equilibrium moves right/less molecules on right hand side
    removing catalyst: does not affect position of equilibrium
    [not too sure about these^]

    Define stereo isomers: have the same structural and molecular formula but different 3D arrangements of atoms in space


    graph with percentages : 195.6 (approx) of something to 1 dp

    i got 96.9% as the yield of something to do with propene (i cant remember)

    got something like 4956 (approx) for the hess cycle question

    4.96 X10-3 moles (of something cant remember again lol)

    820 kjmol-1 as the enthalpy change when 230dm^3 is produces from N2 and O2

    82 kJ as the next answer

    on the mass spec

    For yeast question:
    C6h12o6 ---> c2h50h + h20 (i forgot to balance do i lose a mark?)

    CFCs - biodegradable alternatives:
    i wrote HCFCs because i had NO idea, anybody know the answer?

    Mass spec of Sulphur
    M+ was the value of the furthest line to the right
    S8
    the m/z was the base (tallest) peak
    S4+

    free radical question:
    Initiation: IBr ---> I* + Br* (in presence of UV)
    Propagation 1 : Ch4 + Br* ---> Ch3* + HBr
    Propagation 2: ch3* + IBr ----> CH3I + Br*


    for propaation 2 i wrote Ch3* + I* -----> CH3I (but its wrong because its a termination step ! silly me!!!)


    Termination step (any two radicals added)

    The bond fission was homolytic (because 1 e- from the covalent bond goes to each atom)

    Working out the X and Y substances from the IR spec:
    empirical formula gave c4h8O
    i got that it could be an aldehyde or a ketone (due to absorbtions stated)
    i drew the aldehyde and ketone structure but didnt name them, will i lose a mark?

    For the bolztman distribution:
    temp: 2 curves, one lower than the other
    increasing temp1 increases the mean energy of the particles therefore particles collide more and have more successful collisions

    catalyst: 1 curve, 2 activation energy lines shown
    adding a catalyst reduces the activation energy meaning more particles have the sufficient energy required to overcome the energy barrier to react. thus a greater rate of reaction.
    I think in the last question about the bolztman distribution. when talking about temperature i also wrote about your point about more successful collisions but also you should draw on your curve the extra proportion of molecules with greater than the activation energy i think haha
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    (Original post by 344302)
    Oh good! I was doubting myself for a minute !!

    Hey you know the equilibrium question? Did you put left and left or left and right or what.

    I can't even remember . I think I counted the moles wrong for the pressure. Damn
    (Original post by chigyy)
    I got left and left, but I think temperature was right, not to sure.

    Left, left.
    The forward reaction is exothermic, so increasing the temperature will shift it left (towards the endothermic side).
    (Original post by such)
    Increasing pressure favours reverse reaction because there is less pressure on the left (3.5 moles of gas on the left, 4 moles of gas on the right).
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    (Original post by bliam)
    Also, would it matter if I spelled equilibrium incorrectly? My hands wanted to spell it "Equilibreum" I don't know
    I advise that you pick up AS English however I seriously doubt you would drop any marks as it still sound like Equilibrium when one pronounces it.
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    (Original post by chigyy)
    I got left and left, but I think temperature was right, not to sure.
    No temp. was left too because the Q had negative delta H.
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    (Original post by cyiarik)
    A SORT OF UNNOFFICIAL MARK-SChEME (MAY BE OUT OF ORDER)

    First Question
    -
    C10H22
    - (drawn) any branched isomer of c10h22 AND named [ i put 2-methylnonane ]
    - (cracking question) C15H31 ----> C10H20 + C5H12 (any suitable equation-
    - why does cracking hydrocarbons produce many products? C-C bond can break anywhere in the hydrocarbon chain
    - (drawn) cyclo-octane i drew both skeletal and displayed formula of this just in case
    - cyclo-alkanes are made because they burn more efficiently/ have a higher octane rating

    Other question answers :
    - homologous series: molecules that have same functional group but each successive member differs by a CH2
    - burns with black smoke due to imcomplete combustion/ black smoke and yellow flame indicates there was a lack of oxygen therefore it did not combust completely.
    - [question about why does something have 100% atom economy] because there was only 1 product produced in the reaction/ no waste products were produced in the reaction

    Question about weird looking molecule thing showing E/z isomerism:
    - functional groups present were an ester and an alkene (c-c double bond and a c-o double bond o)
    - structure j is different from structure i because in I both the groups are on the same side of the double bond (Z isomerism) whereas in J each group is on the different sides of the c-c double bond (E isomerism)
    Box Drawings for products of Alcohol when
    1-oxidised
    2-reacted with a carboxylic acid
    3-dehydrated/hydrated

    • 1st box was and ester or an aldehyde (may have to draw both)
    • 2nd box was an ester + H20
    • 3rd and 4th boxed were dehydration/hydration

    For the question about halogenoalkanes:
    - most unreactive: i put the first one (N)
    - Most reactive one had 2 halogens in it (I and Br)

    - P had a lower b/p than Q because P contained Br and Q contained I. The C-I bond is longer than the C-Br bond, thus it is easier to overcome the C-I bond as it experiences less attraction to the nucleus of the C atom/ takes less energy to overcome C-I bond.

    Had to choose one of the halogenoalkanes to demonstrate electrophilic addition (1) + diagram

    For the Le chatelier question:
    increasing temp: favours reverse reaction/position shifts to reduce temp, backward reaction endothermic
    Increasing pressure: favors forward reaction, position of equilibrium moves right/less molecules on right hand side
    removing catalyst: does not affect position of equilibrium
    [not too sure about these^]

    Define stereo isomers: have the same structural and molecular formula but different 3D arrangements of atoms in space


    graph with percentages : 195.6 (approx) of something to 1 dp

    i got 96.9% as the yield of something to do with propene (i cant remember)

    got something like 4956 (approx) for the hess cycle question

    4.96 X10-3 moles (of something cant remember again lol)

    820 kjmol-1 as the enthalpy change when 230dm^3 is produces from N2 and O2

    82 kJ as the next answer


    For yeast question:
    C6h12o6 ---> c2h50h + h20 (i forgot to balance do i lose a mark?)

    conditions of fermentation reaction: 37 degrees Celsius (not sure if this counts), fermentation is anaerobic therefore NO OXYGEN, yeast as catalyst


    CFCs - biodegradable alternatives:
    i wrote HCFCs because i had NO idea, anybody know the answer?

    Mass spec of Sulphur
    M+ was the value of the furthest line to the right
    S8
    the m/z was the base (tallest) peak
    S4+

    free radical question:
    Initiation: IBr ---> I* + Br* (in presence of UV)
    Propagation 1 : Ch4 + Br* ---> Ch3* + HBr
    Propagation 2: ch3* + IBr ----> CH3I + Br*


    for propaation 2 i wrote Ch3* + I* -----> CH3I (but its wrong because its a termination step ! silly me!!!)


    Termination step (any two radicals added)

    The bond fission was homolytic (because 1 e- from the covalent bond goes to each atom)

    Working out the X and Y substances from the IR spec:
    empirical formula gave c4h8O
    i got that it could be an aldehyde or a ketone (due to absorbtions stated)
    i drew the aldehyde and ketone structure but didnt name them, will i lose a mark?

    For the bolztman distribution:
    temp: 2 curves, one lower than the other
    increasing temp1 increases the mean energy of the particles therefore particles collide more and have more successful collisions

    catalyst: 1 curve, 2 activation energy lines shown
    adding a catalyst reduces the activation energy meaning more particles have the sufficient energy required to overcome the energy barrier to react. thus a greater rate of reaction.
    I thought it was 195.2 for the relative abundance question? Also, there's how does stratosphere maintain ozone layer and the question after that about NO
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    (Original post by jacksonmeg)
    anyone got link to the paper ?
    This is part of it http://examwizard.yolasite.com/resources/Scan-12.pdf
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    (Original post by cyiarik)
    A SORT OF UNNOFFICIAL MARK-SChEME (MAY BE OUT OF ORDER)

    First Question
    -
    C10H22
    - (drawn) any branched isomer of c10h22 AND named [ i put 2-methylnonane ]
    - (cracking question) C15H31 ----> C10H20 + C5H12 (any suitable equation-
    - why does cracking hydrocarbons produce many products? C-C bond can break anywhere in the hydrocarbon chain
    - (drawn) cyclo-octane i drew both skeletal and displayed formula of this just in case
    - cyclo-alkanes are made because they burn more efficiently/ have a higher octane rating

    Other question answers :
    - homologous series: molecules that have same functional group but each successive member differs by a CH2
    - burns with black smoke due to imcomplete combustion/ black smoke and yellow flame indicates there was a lack of oxygen therefore it did not combust completely.
    - [question about why does something have 100% atom economy] because there was only 1 product produced in the reaction/ no waste products were produced in the reaction

    Question about weird looking molecule thing showing E/z isomerism:
    - functional groups present were an ester and an alkene (c-c double bond and a c-o double bond o)
    - structure j is different from structure i because in I both the groups are on the same side of the double bond (Z isomerism) whereas in J each group is on the different sides of the c-c double bond (E isomerism)
    Box Drawings for products of Alcohol when
    1-oxidised
    2-reacted with a carboxylic acid
    3-dehydrated/hydrated

    • 1st box was and ester or an aldehyde (may have to draw both)
    • 2nd box was an ester + H20
    • 3rd and 4th boxed were dehydration/hydration

    For the question about halogenoalkanes:
    - most unreactive: i put the first one (N)
    - Most reactive one had 2 halogens in it (I and Br)

    - P had a lower b/p than Q because P contained Br and Q contained I. The C-I bond is longer than the C-Br bond, thus it is easier to overcome the C-I bond as it experiences less attraction to the nucleus of the C atom/ takes less energy to overcome C-I bond.

    Had to choose one of the halogenoalkanes to demonstrate electrophilic addition (1) + diagram

    For the Le chatelier question:
    increasing temp: favours reverse reaction/position shifts to reduce temp, backward reaction endothermic
    Increasing pressure: favors forward reaction, position of equilibrium moves right/less molecules on right hand side
    removing catalyst: does not affect position of equilibrium
    [not too sure about these^]

    Define stereo isomers: have the same structural and molecular formula but different 3D arrangements of atoms in space


    graph with percentages : 195.6 (approx) of something to 1 dp

    i got 96.9% as the yield of something to do with propene (i cant remember)

    got something like 4956 (approx) for the hess cycle question

    4.96 X10-3 moles (of something cant remember again lol)

    820 kjmol-1 as the enthalpy change when 230dm^3 is produces from N2 and O2

    82 kJ as the next answer


    For yeast question:
    C6h12o6 ---> c2h50h + h20 (i forgot to balance do i lose a mark?)

    conditions of fermentation reaction: 37 degrees Celsius (not sure if this counts), fermentation is anaerobic therefore NO OXYGEN, yeast as catalyst


    CFCs - biodegradable alternatives:
    i wrote HCFCs because i had NO idea, anybody know the answer?

    Mass spec of Sulphur
    M+ was the value of the furthest line to the right
    S8
    the m/z was the base (tallest) peak
    S4+

    free radical question:
    Initiation: IBr ---> I* + Br* (in presence of UV)
    Propagation 1 : Ch4 + Br* ---> Ch3* + HBr
    Propagation 2: ch3* + IBr ----> CH3I + Br*


    for propaation 2 i wrote Ch3* + I* -----> CH3I (but its wrong because its a termination step ! silly me!!!)


    Termination step (any two radicals added)

    The bond fission was homolytic (because 1 e- from the covalent bond goes to each atom)

    Working out the X and Y substances from the IR spec:
    empirical formula gave c4h8O
    i got that it could be an aldehyde or a ketone (due to absorbtions stated)
    i drew the aldehyde and ketone structure but didnt name them, will i lose a mark?

    For the bolztman distribution:
    temp: 2 curves, one lower than the other
    increasing temp1 increases the mean energy of the particles therefore particles collide more and have more successful collisions

    catalyst: 1 curve, 2 activation energy lines shown
    adding a catalyst reduces the activation energy meaning more particles have the sufficient energy required to overcome the energy barrier to react. thus a greater rate of reaction.
    H20 isnt produced in fermentation. For the le chatelier one there were less moles on the left so increasing the pressure would move it to the left not to the right.
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    For the Q=mc(delta)T question, did you guys get 7.06 or something like that, and then the moles was like 0.005 and then it was 7.06/0.005? Please tell me this is relevant to some part to the exam
 
 
 
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