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***2015 LC Chemistry - Higher Level - June 16th***

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    #92
    OMGeary
    Registered Users Posts: 251 ✭✭OMGeary


    Thebabyjesus wrote: »
    and initial concentration of ethanoic acid?

    Got something x10to the power of 10. Know for sure I got that one wrong.


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    #93
    Hydrocerium
    Registered Users Posts: 9 ✭Hydrocerium


    Thebabyjesus wrote: »
    Appearance of phenylmethanol at room temp? Problems than can arise with A and D? and initial concentration of ethanoic acid?

    I just said it was a colourless liquid.
    According to Wikipedia "Benzyl alcohol is a colorless liquid with a mild pleasant aromatic odor."
    I said A didn't have enough chlorine so the water could have harmful bacteria etc in it and for B I said it had too much free chlorine which could irritate the swimmers eyes.
    For the concentration of ethanoic acid I got 0.01395492462 M


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    #94
    Iamtheduchess
    Registered Users Posts: 46 ✭Iamtheduchess


    Thebabyjesus wrote: »
    Appearance of phenylmethanol at room temp? Problems than can arise with A and D? and initial concentration of ethanoic acid?

    A and D of the water samples? Free chlorine concentration?
    I said one was too low- swimmers would get infections/diseases
    Other too high- irritate their eyes


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    #95
    Iamtheduchess
    Registered Users Posts: 46 ✭Iamtheduchess


    Which question was the concentration of ethanoic acid for?


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    #96
    otoolej2
    Registered Users Posts: 35 ✭otoolej2


    Hydrocerium wrote: »
    I just said it was a colourless liquid.
    According to Wikipedia "Benzyl alcohol is a colorless liquid with a mild pleasant aromatic odor."
    I said A didn't have enough chlorine so the water could have harmful bacteria etc in it and for B I said it had too much free chlorine which could irritate the swimmers eyes.
    For the concentration of ethanoic acid I got 0.01395492462 M

    ye i got the same answer for the initial concentration of ethanoic acid. it was quite a tricky question, hope its right.


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    #97
    Yokes
    Registered Users Posts: 4 ✭Yokes


    Am I the only one who thought that was easy?
    Iodine-thiosulphate titration is extremely straightforward, anyone with mathematical ability shouldn'tve had any problem with either calculations - it paid off to memories the molecular masses of phenylmethanol and benzoic acid, should've been common sense if it was likely to be asked.
    Short questions nothing strange, q5 was wordy but anyone who learned off theory in depth wouldve cherished that question. Fuels/heats question was standard, catalysis of methanol to methanal using platinum came up before, basic catalytic theory involved in the question.
    Question 8 was a bit tricky, just had to realise the difference between primary and secondary alcohols, reduction of carbonyl compounds theory.
    Question 9 again standard, with the calculation working backwards. 10 (a) structure of benzene is only required at higher level so attention should've been paid particularly towards it - electron delocalisation and intermediate bond lengths etc...
    10c basic stoichiometry
    11 a basic knowledge of trends in the periodic table
    11b was different but calculations were no different, only asked for the number of gaseous moles at equilibrium not the actual equilibrium concentration.
    Honestly fairly standard paper, those who understand the subject flew through it and came out delighted


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    #98
    AulBiddy
    Registered Users Posts: 348 ✭✭AulBiddy


    It wasn't too bad a paper but it was just plain weird! I liked the pool question, question 5 was nice, so was question 6. I struggle a bit with the maths though so I've lost a lot of marks :(


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    #99
    emma35
    Registered Users Posts: 40 ✭emma35


    I said for two advantages of hydrogen as a fuel that it has a high heat of combustion and that it is readily available both of which are true do you think they will be accepted though?


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    #100
    eman129
    Registered Users Posts: 3 ✭eman129


    Am i the only one who just doesn't get chemistry? i took the OL paper after dropping down a few months ago, and i just literally can't comprehend how people are going for a1's in HL. Chemistry is the only OL subject I do as I have applied maths as an 8'th subject. Going for about 550 so i'd say i'm quite intelligent but i just dont get chemistry, and it seem like everyone else does and are all achieving highly in it. Anyone have any opinions on this?


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    #101
    GavD97
    Registered Users Posts: 7 ✭GavD97


    I thought it was lovely. It was strange, in that there were lots of calculations, and something's were changed a bit. I have no idea how I got on but I was happy. Loved all of organic, except for the boiling points part. 👊


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    #102
    Broseph
    Registered Users Posts: 109 ✭✭Broseph


    The_N4sir wrote: »
    I definitely got that wrong I got around 60%:P
    Not having the equation threw me off for that part

    yeah I got 58% I think it's right a lot of the A students in my year got it

    Unsure Questions:
    Q2- changes observed in the reaction vessel after addition of compounds A and B?
    Q3 reagent to detect free chlorine?
    Q4 (h) the larger atom and smaller atom one? Thought there was a trick
    Q6 Properties of hydrogen that make it a good fuel? Said non polluting and a high kilogram calorific value?
    Q11(b) Number of gaseous molecules? I got 20 but then doubled it as there was A AND B and put down 40 as my answer.
    Also I said it was exothermic but then explained all the reasons why this was the case (which all indicated endothermic) but I said exothermic how much do I lose?
    And finally explain how increase in temperature effects the pressure of the equilibrium mixture?


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    #103
    Iamtheduchess
    Registered Users Posts: 46 ✭Iamtheduchess


    eman129 wrote: »
    Am i the only one who just doesn't get chemistry? i took the OL paper after dropping down a few months ago, and i just literally can't comprehend how people are going for a1's in HL. Chemistry is the only OL subject I do as I have applied maths as an 8'th subject. Going for about 550 so i'd say i'm quite intelligent but i just dont get chemistry, and it seem like everyone else does and are all achieving highly in it. Anyone have any opinions on this?
    It all depends on your teacher , you'd probably like it if you had a good teacher! I was the same until I changed schools and got a better teacher- got a C2 in LC last year and this year going for an A1 !


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    #104
    Broseph
    Registered Users Posts: 109 ✭✭Broseph


    Would you get the marks if you said tertiary treatment of sewage removes nitrates and phosphates which can cause eutrophication?


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    #105
    Alex Meier
    Closed Accounts Posts: 663 ✭✭✭Alex Meier


    Broseph wrote: »
    Would you get the marks if you said tertiary treatment of sewage removes nitrates and phosphates which can cause eutrophication?

    YES


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    #106
    Hydrocerium
    Registered Users Posts: 9 ✭Hydrocerium


    Broseph wrote: »
    Would you get the marks if you said tertiary treatment of sewage removes nitrates and phosphates which can cause eutrophication?

    Isn't that the actual purpose..? That's what I said anyway :p


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    #107
    Hydrocerium
    Registered Users Posts: 9 ✭Hydrocerium


    Broseph wrote: »
    Unsure Questions:
    Q2- changes observed in the reaction vessel after addition of compounds A and B?
    Q3 reagent to detect free chlorine?
    Q4 (h) the larger atom and smaller atom one? Thought there was a trick
    Q6 Properties of hydrogen that make it a good fuel? Said non polluting and a high kilogram calorific value?

    Q2. I said that addition of A (HCl) would cause fizzing as it reacted with the excess sodium carbonate and the potassium hydroxide produced in the reaction. Addition of B (sodium sulfite) would cause the brown precipitate of MnO2 in the flask to dissolve as it changed to a +2 oxidation state.

    Q3. DPD No.1 Tablets

    Q4. (h) Na and Be I think (got this one wrong in the exam though)

    Q6. I said that because it only produced water when burned it could be used on board the space shuttle and that it was easily available in large quantities.
    According to NASA's website hydrogen is used because it's a "light and extremely powerful rocket propellant -- has the lowest molecular weight of any known substance and burns with extreme intensity (5,500°F). In combination with an oxidizer such as liquid oxygen, liquid hydrogen yields the highest specific impulse, or efficiency in relation to the amount of propellant consumed, of any known rocket propellant" so any answers that have something like that should be accepted.


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    #108
    Corkgirl18
    Closed Accounts Posts: 894 ✭✭✭Corkgirl18


    eman129 wrote: »
    Am i the only one who just doesn't get chemistry? i took the OL paper after dropping down a few months ago, and i just literally can't comprehend how people are going for a1's in HL. Chemistry is the only OL subject I do as I have applied maths as an 8'th subject. Going for about 550 so i'd say i'm quite intelligent but i just dont get chemistry, and it seem like everyone else does and are all achieving highly in it. Anyone have any opinions on this?

    I think it all depends on your teacher. If you have a decent teacher most students do well. The exam can be predictable and questions are repetitive. If you have a teacher that just reads from the book or whatever it would be impossible for you to get it.


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    #109
    Do You Even Squat
    Registered Users Posts: 90 ✭✭Do You Even Squat


    Hydrocerium wrote: »
    Q4. (h) Na and Be I think (got this one wrong in the exam though)

    I initially said Cl but changed it to Na as the atomic radius would be larger. But atoms after Mg have more electrons in the px, py orbitals etc so i was unsure. Just stuck down Na. is that correct?


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    #110
    The_N4sir
    Registered Users Posts: 213 ✭✭The_N4sir


    I just threw down Na aswell had no clue if it was right


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    #111
    Broseph
    Registered Users Posts: 109 ✭✭Broseph


    A significant difference between an electron in the 2s and 3s orbital of a calcium atom? Ionisation energy?
    And bonds broken and formed in conversion of propanone to propan-2-ol ?


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    #112
    Dingle123
    Registered Users Posts: 7 ✭Dingle123


    Broseph wrote: »
    A significant difference between an electron in the 2s and 3s orbital of a calcium atom? Ionisation energy?
    And bonds broken and formed in conversion of propanone to propan-2-ol ?

    I said 3 p-orbitals between them! I don't know if that's right though


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    #113
    d1234
    Registered Users Posts: 594 ✭✭✭d1234


    I said 3 too!!Hope it's right :)


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    #114
    uzpuz
    Registered Users Posts: 15 ✭uzpuz


    Broseph wrote: »
    yeah I got 58% I think it's right a lot of the A students in my year got it

    Unsure Questions:
    Q2- changes observed in the reaction vessel after addition of compounds A and B?
    Q3 reagent to detect free chlorine?
    Q4 (h) the larger atom and smaller atom one? Thought there was a trick
    Q6 Properties of hydrogen that make it a good fuel? Said non polluting and a high kilogram calorific value?
    Q11(b) Number of gaseous molecules? I got 20 but then doubled it as there was A AND B and put down 40 as my answer.
    Also I said it was exothermic but then explained all the reasons why this was the case (which all indicated endothermic) but I said exothermic how much do I lose?
    And finally explain how increase in temperature effects the pressure of the equilibrium mixture?

    Was endothermic correct? I wrote down endothermic but thought I was wrong.


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    #115
    otoolej2
    Registered Users Posts: 35 ✭otoolej2


    d1234 wrote: »
    I said 3 too!!Hope it's right :)

    no


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    #116
    emma35
    Registered Users Posts: 40 ✭emma35


    Hydrocerium wrote: »
    Q2. I said that addition of A (HCl) would cause fizzing as it reacted with the excess sodium carbonate and the potassium hydroxide produced in the reaction. Addition of B (sodium sulfite) would cause the brown precipitate of MnO2 in the flask to dissolve as it changed to a +2 oxidation state.

    Q3. DPD No.1 Tablets

    Q4. (h) Na and Be I think (got this one wrong in the exam though)

    Q6. I said that because it only produced water when burned it could be used on board the space shuttle and that it was easily available in large quantities.
    According to NASA's website hydrogen is used because it's a "light and extremely powerful rocket propellant -- has the lowest molecular weight of any known substance and burns with extreme intensity (5,500°F). In combination with an oxidizer such as liquid oxygen, liquid hydrogen yields the highest specific impulse, or efficiency in relation to the amount of propellant consumed, of any known rocket propellant" so any answers that have something like that should be accepted.

    im so annoyed with myself for not being more careful with phrasing but do you think if I said high heat of combustion instead of high kilogram calorific value id still get mark? and what about it I said that it is readily available as opposed to having said its the most abundant element on earth, although it is bonded with other atoms naturally...


    also wondering if id get the marks for saying that an electon in the 3s orbital is further from the nucleus than 2s


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    #117
    uzpuz
    Registered Users Posts: 15 ✭uzpuz


    emma35 wrote: »
    im so annoyed with myself for not being more careful with phrasing but do you think if I said high heat of combustion instead of high kilogram calorific value id still get mark? and what about it I said that it is readily available as opposed to having said its the most abundant element on earth, although it is bonded with other atoms naturally...


    also wondering if id get the marks for saying that an electon in the 3s orbital is further from the nucleus than 2s

    You should get the marks.. I said the electron in 2s orbital is more stable which won't be accepted I think


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