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    May 2016
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  1. My teacher decided to write a study guide targetting exam techniques and essay questions. She was wondering if there is a need for this for IB biology students (both HL and SL)? If so, she will start the process and hopefully, we can have it for 2017! My teacher decided to write a study guide targetting exam techniques and essay questions. She was wondering if there is a need for this for IB biology students (both HL and SL)? If so, she will start the process and hopefully, we can have it for 2017! Anyone think this is a good idea?
  2. So originally I thought when you are doing electrolysis, for the aqueous solutions, you always consider between H+ and the metal cation ? So for both of the solutions, hydrogen gas should be discharged preferentially due to a less negative E value number? But why is the answer comparing it to H2O??? Please help
  3. @Msj Chem The link doesn't work, it says you have reached a page that is unavailable for viewing.
  4. Why does pcl5 hv higher melting point than pcl3? I understand that it is cuz it has greater mass/greater number of electrons, hence greater london force, but can't it not equally be argued that pcl5 is non polar because its trigonal bipyramidal and pcl3 is polar and so, theoretically PCl3 should have a higher melting point? Please advise.
  5. For this question, part (e)(ii) I don't understand how the answer could be so simple. I tried a very long-winded way to prove that it was, but the answer simply says as the parameter t >0, therefore D would not lie between A and B?? Does anyone understand the logic behind this? I have also attached the mark scheme. Any comments would be greatly appreciated! Thanks!
  6. cccc

    Random Errors

    For this question, I chose B, as random error could be due to human error, however, the answer is C. I can understand why it is C, but I don't understand why B is not the right answer. Any advice will be appreciated
  7. @kw0573 Thanks! But as this is paper 1, any alternative method to get the answer, as we can't compare electrode potential values? (as we won't be able to access the data booklet)
  8. @Msj Chem It is from 2012 paper. As it is paper 1, we won't be allowed to use the data booklet, therefore won't be able to get those values and compare them. Is there any other way? Thanks
  9. Hi, this question was from a past paper, and I got stuck between choosing C or D, I know the electrode potential (E) should be greater than 0. But what i am stuck with is which one is better reducing agent/ oxidising agent, because it doesn't seem like a fair comparison. Usually we would be comparing between Fe3+ and Br-; and then Fe2+ and Br2. Not the mixture of them together. How to approach these questions? P.S. The answer to this question is D Any help would be greatly appreciated
  10. @kw0573Thank you very much! However, my query is also this: I understand what u said abt the reflection on the real axis and the signs, but the 8 pi/5 thing corresponds to 3 pi/5 and not 2pi/5 so cannot cancel out with the 2pi/5 one in the first term?
  11. Hi, I have a slight query on the following question. This is from a higher level paper (i have attached both the question and the answer) For part (c) I don't know how they could exchange 8pi/5 with 2 pi/5 and don't quite understand the sign changes. This goes with 6pi/5 to be replaced with 4pi/5 Because if you draw out the CAST diagram cos 8 pi/5 should be in the A qudrant (from 0 to pi/2) which means that both cosine and sine should be positive? and not cosine being positive and sine being negative as the answer suggested. Any advice would be great! Thanks.
  12. The question is this: at 25 degrees C, 200 cm^3 of 1 mol dm^3 of nitric acid is added to 5g of magnesium powder. If experiment is repeated using same mass of magnesium powder, which conditions will result in the same initial reaction rate? I chose 100 cm^3 of nitric acid , 2 mol dm^3 as conc and 25 degrees C. However, the answer is 100 cm ^3 of 1 mol dm^3 HNO3. How is it the case? If it is so, then in 200 cm^3, there would be 2 mol dm^3. As there is a higher conc, then the reaction rate should be higher, so it doesn't give the same rate?
  13. Can anyone help me with this question? My queries: 1. I don't really understand the question. 2. So far, I've only got RL (radius of large circle)=2RS (radius of small circle)
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