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

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Comments

  • #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?


  • #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 !


  • #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?


  • #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


  • #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


  • #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.


  • #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.


  • #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?


  • #110
    The_N4sir
    Registered Users Posts: 213 ✭✭The_N4sir


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


  • #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


  • #113
    d1234
    Registered Users, Registered Users 2 Posts: 594 ✭✭✭d1234


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


  • #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.


  • #115
    otoolej2
    Registered Users Posts: 35 ✭otoolej2


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

    no


  • #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


  • #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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