Msj Chem

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    May 2016
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  1. Maybe this will help:
  2. Ka is the acid dissociation constant and Q is the reaction quotient. Do you mean Kc and Q? Is so, maybe this video will help:
  3. Maybe this video will help:
  5. You are free to answer whichever option you want in the exam. My advice would be to answer the option that you have studied before of course.
  6. At SL, you only need to know that halogenoalkanes undergo SN reactions to form alcohols. The mechanisms and kinetics (unimolecular and bimolecular) are not required at SL.
  7. 28. The aluminum ion has a high charge density and is able to hydrolyse water molecules to produce H+ ions in solution and a decrease in pH. 29. A buffer solution should have equal amounts of a weak acid and the salt of the weak acid and strong base. Whichever choice gives you that is the correct answer.
  8. I have worksheets for this topic on my website. Maybe they will be helpful.
  9. From May 2016 subject report (Copyright IB). Component grade boundaries Grade: 1 2 3 4 5 6 7 Mark range: 0 - 3 4 - 6 7 - 10 11 - 13 14 - 16 17 - 19 20 - 24
  10. You can find two videos on pH curves on my website here: Syllabus details can be found here, (see 18.3 pH curves).
  11. 10.0 mol of C2H3Cl would require 25 mol of O2 to react completely because of the 2:5 molar ratio. 10.0 mol of O2 requires 4 mol of C2H3Cl to react and seeing as we have 10.0 mol, that makes O2 the limiting reactant. The ratio of the limiting reactant O2 to H2O is 5:2, therefore 10.0 mol of O2 will produce 4 mol of H2O.
  12. It all comes down to personal preference, I prefer the Pearson chemistry textbook to the Oxford textbook mainly due to the fact that it comes in separate SL and HL versions and has a good range of practice exam questions. The study guide is good for revising but lacks the detail of a textbook. As far as I know there isn't another study guide available for IB chemistry. If you are looking for chemistry video tutorials, then I have videos that cover almost the whole syllabus. A lot of videos also have worksheets to accompany them.
  13. Each option is assigned 15 hours at SL with an additional 10 hours for HL, giving a total of 25 hours teaching time. So what you are proposing is an extra 75 hours of teaching time to cover all 4 options. I can't speak for your teacher but I don't think that it would be possible for your teacher to teach you all 4 options when there is no requirement to do so. Of course you are free to study all 4 options and some further organic chemistry yourself but that depends on how much free time you have. I have videos that cover almost all of the option topics here:
  14. There are two ways to calculate this. One way is to use the Kw to find the [H+], and then use pH = -log [H+] The second way is to use pOH = -log[OH-] There is a mistake in the mark scheme, it should read -log (3.98 x10-3) = 2.4,
  15. "I don't quite understand the reactions involving ammonia solution, like are both NH4+ and NH3 are present there?" HCl reacts with NH3 to produce NH4Cl HCl + NH3 ==> NH4Cl The NH3 is the excess reactant which is why you have some left over. The NH4+ comes from the dissociation of the salt NH4Cl (assume that the salt fully dissociates). "Why do we have to know the final amount of them both and where did it come from?" You have equal final concentrations of NH3 and NH4+ which acts as a buffer solution. Subtract the amount in mol that reacted from the initial amount in mol. Use the equation C=n/V to get the concentration. Use the Henderson-Hasselbach equation (like in the previous example you posted) to calculate the pH and pOH.