Usman Khan Posted May 18, 2013 Report Share Posted May 18, 2013 I had D for the graph because of the gradientPerhaps it is D, and that they wanted us to recognize that C only worked for a second order reaction. From a mathematical perspective, I think that the question was unfair.The answer was definitely C for that question. First order reactions come very close to zero in a []/t graph, whereas second order graphs are much less steep. I agree it was a trick question, but luckily I had a look at those graphs in my textbook the night before Reply Link to post Share on other sites More sharing options...
SurajM Posted May 18, 2013 Report Share Posted May 18, 2013 Does anybody know what the grade boundaries will be like for this year? #soscared Reply Link to post Share on other sites More sharing options...
JohnSmith Posted May 18, 2013 Report Share Posted May 18, 2013 Yeah that meniscus stuff was weird... Did not like that at all... I also wrote random error but it was a complete guess. My friend wrote human error which could actually be right...If anyone did the orgo question, I thought the one where you had to find the molecular formula of menthol was such a smart question. Took me a while but I got it.Did anyone do the HF question? That's the only one I had no idea about... Reply Link to post Share on other sites More sharing options...
Usman Khan Posted May 18, 2013 Report Share Posted May 18, 2013 Does anybody know what the grade boundaries will be like for this year? #soscaredPaper one usually fluctuates around 35-36/40 for a 7, and should be the same this year as it wasn't hugely harder than previous years. i hope grade boundaries are lower for paper two this year, because of that stupid question A data analysis. Usually a 7 is around 69-71/90 so hopefully this year it will be a bit lower like 66 or something. It won't be a huge difference though. Reply Link to post Share on other sites More sharing options...
Usman Khan Posted May 18, 2013 Report Share Posted May 18, 2013 Yeah that meniscus stuff was weird... Did not like that at all... I also wrote random error but it was a complete guess. My friend wrote human error which could actually be right...If anyone did the orgo question, I thought the one where you had to find the molecular formula of menthol was such a smart question. Took me a while but I got it.Did anyone do the HF question? That's the only one I had no idea about...Yeah the molecular formula question was straight from november 2012, I couldn't believe they put it again! For the HF question you have to calculate the pKb of F-, and pKa of NH4+ and compare which one is lower. Since NH4+ is lower, it is stronger so the solution will be acidic. Reply Link to post Share on other sites More sharing options...
Johanna St Posted May 18, 2013 Report Share Posted May 18, 2013 I said it was a systematic error, as the readings would have all been off by the same amount. And I said that they should reduce the amount of oxygen available, as the percipitate formed in the reaction of Mn2+ with oxygen. but I am not sure they'll accept it, I just guessed for that oneThe thing is, this isn't even in the syllabus. Let's bomb the IB in Cardiff!!!!What isn't in the syllabus ? The systematic error thing is (objective 11.1.1 describe and give examples of random uncertainties and systematic errors). And for the Mn thing, who knows, i guess it is just data analysis... But I'll join the bombing anyways Reply Link to post Share on other sites More sharing options...
IB-Adam Posted May 18, 2013 Report Share Posted May 18, 2013 I said it was a systematic error, as the readings would have all been off by the same amount. And I said that they should reduce the amount of oxygen available, as the percipitate formed in the reaction of Mn2+ with oxygen. but I am not sure they'll accept it, I just guessed for that oneThe thing is, this isn't even in the syllabus. Let's bomb the IB in Cardiff!!!!What isn't in the syllabus ? The systematic error thing is (objective 11.1.1 describe and give examples of random uncertainties and systematic errors). And for the Mn thing, who knows, i guess it is just data analysis... But I'll join the bombing anyways I meant the percipitate which was formed. I simply guessed that MnO was formed. Haha, perfect! Reply Link to post Share on other sites More sharing options...
Johanna St Posted May 18, 2013 Report Share Posted May 18, 2013 What were other peoples answers for reducing the amount of MnO formed ? I mean reducing the amount of oxygen supplied during the reaction does not seem realistic and doable to me Reply Link to post Share on other sites More sharing options...
spacemonkey74 Posted May 18, 2013 Report Share Posted May 18, 2013 @usman khanWhat did u get for the molecular formula? I got the empirical formula itself as the molecular? Reply Link to post Share on other sites More sharing options...
Usman Khan Posted May 18, 2013 Report Share Posted May 18, 2013 Same ! I think I got something like C10H20O Reply Link to post Share on other sites More sharing options...
SurajM Posted May 18, 2013 Report Share Posted May 18, 2013 I said it was a systematic error, as the readings would have all been off by the same amount. And I said that they should reduce the amount of oxygen available, as the percipitate formed in the reaction of Mn2+ with oxygen. but I am not sure they'll accept it, I just guessed for that oneThe thing is, this isn't even in the syllabus. Let's bomb the IB in Cardiff!!!!What isn't in the syllabus ? The systematic error thing is (objective 11.1.1 describe and give examples of random uncertainties and systematic errors). And for the Mn thing, who knows, i guess it is just data analysis... But I'll join the bombing anyways That error comes under systematic errors, its known as a parallax error. I only know this because of the many titration experiments we did over the two years lol. My teacher mentioned it many times Reply Link to post Share on other sites More sharing options...
spacemonkey74 Posted May 18, 2013 Report Share Posted May 18, 2013 @ usman khanYes that's what i got as well Reply Link to post Share on other sites More sharing options...
spacemonkey74 Posted May 18, 2013 Report Share Posted May 18, 2013 And yes that is a systematic error, if read from the same angle wrongly each time. As i remeber it said it was read above the meniscus each time so it was defintely systematic Reply Link to post Share on other sites More sharing options...
Rohan Madhwal Posted May 19, 2013 Report Share Posted May 19, 2013 Yeah that meniscus stuff was weird... Did not like that at all... I also wrote random error but it was a complete guess. My friend wrote human error which could actually be right...If anyone did the orgo question, I thought the one where you had to find the molecular formula of menthol was such a smart question. Took me a while but I got it.Did anyone do the HF question? That's the only one I had no idea about...I did the HF question. Well urhh, i could have been wrong but basically what i did was i converted the Ka to the pKa and then I deduced that it was a weak acid (which HF is). Then I stated the Kb for the other one, converted it to its pKb, deduced that it was a weak base. Said that the weak acid would form a strong conjugate base and the weak base would form a strong conjugate acid, therefore, they would both be neutralized and hence the resulting solution is neutral. Reply Link to post Share on other sites More sharing options...
Ibomorelikeibno Posted May 20, 2013 Report Share Posted May 20, 2013 I teared in the exam out of frustration. Are you kidding me IB?! Paper 2 was the hardest thing I have ever been given. I used to solve past papers and score 5 and above. I go into the exam and I am absolutely shocked, my future is at risk because of chemistry right now. paper 1 was really easy though, I knew something bad was going to happen with Paper 2 since the same scenario occurred with Math Paper 2. Reply Link to post Share on other sites More sharing options...
-._._.- Posted May 20, 2013 Report Share Posted May 20, 2013 That error comes under systematic errors, its known as a parallax error. I only know this because of the many titration experiments we did over the two years lol. My teacher mentioned it many timesI put parallax too but I wasn't sure because parallax is like you reading the scale at an angle. But the students are totally reading it wrongly (I actually think it is because they don't know how to read ). I mean it is not that they are reading at an angle. They are just taking the wrong measurements. Reply Link to post Share on other sites More sharing options...
JohnSmith Posted May 21, 2013 Report Share Posted May 21, 2013 I got C10H20O as well and that's the right formula for menthol http://en.wikipedia.org/wiki/Menthol Reply Link to post Share on other sites More sharing options...
yueee Posted June 26, 2013 Report Share Posted June 26, 2013 I did 3 questions in paper 2 section B. does anyone knw how they mark it? Do they mark the best 2 scores or just the first two that I wrote on the cover sheet? Reply Link to post Share on other sites More sharing options...
Blewey Posted September 6, 2013 Report Share Posted September 6, 2013 Hi. Do you guys know if and where i could find these exams on the web?Am looking for the more recent exams for practice. Reply Link to post Share on other sites More sharing options...
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