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    May 2010
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    Sri Lanka
  1. Parami143_Kella

    Chemistry past paper questions

    Not to be an ass... but nope, it's C for 17. Reactant particles could collide with insufficient activation energy/wrong geometry and not react. Sure about this? According to the collision theory, the colliding particles need to, amongst other things 1. Have enough energy to react 2. Collide with the right geometry And increased frequency of collision (i.e increased concentration) will lead to more collsions. So if I'm correct, all options given are correct, and therefore the answer is D. So in a complete combustion CO2 is formed? Sounds familiar... Increased collision doesn't guarantee all particles have sufficient energy or the right geometry. Now, provided that these 2 requirements are satisfied, yes, the reaction rate is affected. So it's kind of a trick question... which I'm not too sure of the answer to now because of the wording. Someone check the answer please. But increased frequency will increase the rate of reaction. It doesn't matter how high energy they have, if they don't meet, they won't react. There will always be collisions between particles, that's a given. I'm not arguing this, haha. Someone check the answer, please. From what i know, heat increases the collision frequency and hence collision frequncy does affect the rate of reaction. However, like Irene said, for a collision to occur it requires energy and the correct geometry. However, the question does not state if the reaction has already started or not. I think in this question the collision frequency does affect the rate of reaction. But someone should check the answer:) i will look for it. And yes Tilia CO2 is produced in complete combustion and in incomplete it is usually CO or just C.
  2. Parami143_Kella

    Chemistry past paper questions

    They are asking which ones are incomplete combustions. The first one is complete combustion Right. But how can you tell that the first is a complete one? Ok we have three equations in the question. During complete combustion, there is enough oxygen for the fuel to burn ans as a result carbon dioxide(prodcut)is formed. However, during incomplete combustion there is a lack of oxygen therefore resulting in an inability to form carbon dioxide. In many cases during incomplete combustion carbon monoxide will be formed. Now in the question given, the first equation has formed carbon dioxide but the other two equations haven't. Therefore we can say that the other two is incomplete combustion since carbon dioxide is not formed. Basically just look to see if there is carbon dioxide formed in the products or not if you are given a question like this. Hope that made sense.
  3. Parami143_Kella

    Chemistry past paper questions

    They are asking which ones are incomplete combustions. The first one is complete combustion
  4. Parami143_Kella

    Chemistry past paper questions

    The answer is D for question 17 and the answer is C for question 29. if you could tell which parts you were confused about i will clarify your doubts.
  5. Parami143_Kella

    Chemistry past paper questions

    i don't know if i am correct but i think these questions are testing your understanding of the Avogadro constant especially question 4. When i did the math i got 2. as C and 4 as D. And if i am wrong anybody is free to correct me. You have to remember the formulas they taught you at school like moles= mass/Mr and so on. We should also know for example if we take carbon its molecular mass is 12g or more precisely 12.01 g. What this means is 1 mole of carbon is 12.01g. 1 mole of carbon or 12.01g of carbon equal to 6.02 X 10^23 atoms, this is the avogadro constant as you may know. We should understand this rule in order to the questions. Now 1.01 g of Hydrogen which is the molecular mass of hydrogen in the periodic table is 6.02X 10^23 too. This is because 1 mole of Hydrogen equals 1.01 g. now I will show you how I did the question. Hope my wording isnt confusing:P Q2. A. 6.02 X 10^23 → 1 mole of H2 therefore 1.01g = that is the value of A. B. We can use formula : moles= mass/ mr for this one : 5 moles = mass/ 20.18( mr value in periodic table) Mass= 5 X 20.18 which equals 100.9g. C. 6.02 X 10^23 atoms → 1 mole of silver therefore 107.87g and then the number of grams for 1.2X10^24 atoms is unknown. So we cross multiply consider the unknown as x. 6.02x10^23→ 107.87g 1.2X10^24→ x When we cross multiply and make x the subject we get: 107.87X (1.2 X 10^24)/ 6.02 X 10^23 and this equals to 215g to 3 significant figures. So the grams this is 215g D. Then D is jus simple it 1.7 X 10^2 g which is the same 170g. Now looking at all the values you found out the biggest mass is evidently 215g. So the answer would be © I dont know if my answers are correct I doubled checked but that is how u do it if I am not wrong. If that was helpful let me know and Ill show you how I did the next question.
  6. Parami143_Kella

    Kinetics Help in Chemistry

    Well our teacher told us to look at the rate of reaction then look at the concentration and see how the rate increases or decreases with the concentration. That's why i got confused. But thank you for your help. Thank both of you.
  7. Parami143_Kella

    Kinetics Help in Chemistry

    Hi! I do chemistry HL and in exams i always get the order of reaction correct but i don't get the reason correct. So could somebody please help me understand the reason for obtaining a certain order of reaction. Thank you. I have attached a past paper. I was doing the first question.
  8. Parami143_Kella


    Hi! Im starting Japanese language B starting yr 13 since I'm struggling with Italian abintio. I've lived in Japan for 4 yrs and i learnt it for 4 yrs but our school does not have Japanese teacher now i have to go through the syllabus alone with the help of my dad. I bought the book Basic kanji book volume 2 but it doesn't have all the Kanji i need only some. If you can please tell me where i can find the first 500 Kanji on the net. Thank you.
  9. Parami143_Kella

    World Lit Assignment 1

    I hate it too it gives you a sense of clusterphobia. As if u were trapped and could not breathe. I thought it was easier to compare it with "Like Water for chocolate" the whole idea of the ghost and the guilt. Don't you feel that Emile Zola's being extremely scientific? I believe he represents the later relationship of Laurent and Therese with such indifference and as i mentioned before makes u feel so trapped and clusterphobic. I suppose it's written in an interesting way.
  10. Parami143_Kella

    World Lit Assignment 1

    The ghost of Therese's husband Camille that both Laurent and Camille sees. The fact that its just the two of them seeing it i believe is a representation of guilt.
  11. Parami143_Kella

    World Lit Assignment 1

    I would have to agree and that's why with advice from you all especially i've restructured my title to "Representation of guilt of the protaganist through supernatural elements in Like Water For Chocolate and Therese Raquin. I especially aknowledge what desi_dakku said. But thank you everyone:)
  12. Parami143_Kella

    [A1] Oral Commentaries -- Tips?

    Your presentation must be formal. You can't say stuff like "this happened like 'you know'" i don't know that's just an example. Also structure your presentation so each point links to the other. Speak with confidence
  13. Parami143_Kella

    World Lit Assignment 1

    Thank You
  14. Parami143_Kella

    World Lit Assignment 1

    Is this title good? Does it sound right? How does the element of supernatural help represent guilt in the protagonists of Like Water for Chocolate and Therese Raquin?
  15. Parami143_Kella

    Percentage uncertainty

    Yes titration can be used for acid/ base.

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