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Chemistry HL Paper 1 & Paper 2 Discussion

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I think Paper 2 was the hardest one for this new syllabus so far, and I made a lot of dumb mistakes on Paper 3. At this point doesn't seem like my IA will even help as much lmao just hoping to scrape a 70/95 for Paper 2 and 34/45 for Paper 3. 

A lot of the questions were worth 1-3 marks and there were a lot I didn't have 100% the answer to, so I might have lost about 15ish marks on those small ones, and I got the structural formulas and splitting patterns for the HNMR thing wrong (lose 3 marks). Not to mention the Bohr Hydrogen Emission Spectrum too lmao, another 2 marks gone. Do you remember your answers to the enthalpy questions on the very last page of Paper 2?

Paper 1 was slightly easier, but I still made a few really dumb mistakes. For the standard zinc electrode I was told that the answer was +0.34V. Apparently you needed to make the reduction potential of Zinc to 0 as it was now "Standard Zinc Electrode", but then you don't reverse the sign for Cu as Zinc is still above Cu in the activity series (like hell we were supposed to remember that without our data booklets), therefore just summation: 0 + (+0.34) = +0.34V.

For the Born-Haber Cycle question, I summed up all values as positive except for the very last one, which I made it negative since it was electron affinity (the equation was K2+ + 2e + O), but I've been hearing a lot of people say they just sum up all values as positive.

I think Li came up as the answer twice for different questions. Also put C2H4 as being a species that can be reduced due to addition of hydrogen and the reaction being electrophilic addition (oxidation number of Carbon also decreases). 

Ratio for gas was 1:2 I believe, in comparison with what other people discussed. 

For the last questions: the synthesis of Phenylamine was a nice question imo, and the graph for "n" vs "Temperature" is the shape of y = (1/x); one hydrogen environment in the HNMR, x-ray crystallography as the final answer. Do you remember the letter answer you placed for the "Secondary Carbon" one? 

 

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4 hours ago, IB`NOT`ez said:

I think Paper 2 was the hardest one for this new syllabus so far, and I made a lot of dumb mistakes on Paper 3. At this point doesn't seem like my IA will even help as much lmao just hoping to scrape a 70/95 for Paper 2 and 34/45 for Paper 3. 

A lot of the questions were worth 1-3 marks and there were a lot I didn't have 100% the answer to, so I might have lost about 15ish marks on those small ones, and I got the structural formulas and splitting patterns for the HNMR thing wrong (lose 3 marks). Not to mention the Bohr Hydrogen Emission Spectrum too lmao, another 2 marks gone. Do you remember your answers to the enthalpy questions on the very last page of Paper 2?

Paper 1 was slightly easier, but I still made a few really dumb mistakes. For the standard zinc electrode I was told that the answer was +0.34V. Apparently you needed to make the reduction potential of Zinc to 0 as it was now "Standard Zinc Electrode", but then you don't reverse the sign for Cu as Zinc is still above Cu in the activity series (like hell we were supposed to remember that without our data booklets), therefore just summation: 0 + (+0.34) = +0.34V.

For the Born-Haber Cycle question, I summed up all values as positive except for the very last one, which I made it negative since it was electron affinity (the equation was K2+ + 2e + O), but I've been hearing a lot of people say they just sum up all values as positive.

I think Li came up as the answer twice for different questions. Also put C2H4 as being a species that can be reduced due to addition of hydrogen and the reaction being electrophilic addition (oxidation number of Carbon also decreases). 

Ratio for gas was 1:2 I believe, in comparison with what other people discussed. 

For the last questions: the synthesis of Phenylamine was a nice question imo, and the graph for "n" vs "Temperature" is the shape of y = (1/x); one hydrogen environment in the HNMR, x-ray crystallography as the final answer. Do you remember the letter answer you placed for the "Secondary Carbon" one? 

 

I'm not agree with u on that standard electrode question.. If u used the zinc electrode as the SHE, then u also need to take into account the potential diff between Zn and H electrode which is -0.76 V.. Then do the sign reversion, which will give you the value of 1.1 V. I'm 100% sure about this..

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9 minutes ago, 45'er said:

I'm not agree with u on that standard electrode question.. If u used the zinc electrode as the SHE, then u also need to take into account the potential diff between Zn and H electrode which is -0.76 V.. Then do the sign reversion, which will give you the value of 1.1 V. I'm 100% sure about this..

That makes sense.

 

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1 hour ago, IB`NOT`ez said:

That makes sense.

 

 
 

I think it was 0.34 cuz they asked for the electrode potential of cu only.. and wasn't it IR spectroscopy for the last one cuz it was something about bonds absorbing energy as far as I remember.. 

and for the affinity one I think you just to turn all of the arrows in the same direction and in that case you had to turn the one for Hf which makes it positive.. so yeah all were positive. 

I got the structure wrong too. wasted a lot of time on that but still, couldn't figure it out.

Edited by IB2017student

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54 minutes ago, IB2017student said:

I think it was 0.34 cuz they asked for the electrode potential of cu only.. and wasn't it IR spectroscopy for the last one cuz it was something about bonds absorbing energy as far as I remember.. 

and for the affinity one I think you just to turn all of the arrows in the same direction and in that case you had to turn the one for Hf which makes it positive.. so yeah all were positive. 

I got the structure wrong too. wasted a lot of time on that but still, couldn't figure it out.

The last one was definitely X ray..

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2 hours ago, 45'er said:

Anyway guys, what was the last question in P2 TZ2 once again?

Enthalpy calculations. Do you remember any possible answers? I think for the temperature at which reaction becomes spontaneous was a high number, about 900~ or something. 

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3 hours ago, IB2017student said:

I think it was 0.34 cuz they asked for the electrode potential of cu only.. and wasn't it IR spectroscopy for the last one cuz it was something about bonds absorbing energy as far as I remember.. 

and for the affinity one I think you just to turn all of the arrows in the same direction and in that case you had to turn the one for Hf which makes it positive.. so yeah all were positive. 

I got the structure wrong too. wasted a lot of time on that but still, couldn't figure it out.

The final enthalpy change was definitely negative, since the equation right before the final enthalpy arrow was electron affinity, which is always exothermic. Enthalpy change of formation you were right in making it positive, but electron affinity must be negative. 

Not sure about the electrode potential question, I think @45'er has the right of it. 

I gave a structure that had the 2:3:9 ratio, but I forgot that they all had singlet splitting patterns and my structure didn't conform to that. 

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4 minutes ago, IB`NOT`ez said:

Enthalpy calculations. Do you remember any possible answers? I think for the temperature at which reaction becomes spontaneous was a high number, about 900~ or something. 

U sure? It's pH calculation as I remembered (?) I'm in TZ2 once again..

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5 minutes ago, 45'er said:

U sure? It's pH calculation as I remembered (?) I'm in TZ2 once again..

Yeah I remember there were pH calculations: [H+] of NaOH, pKA = 5, another method to determine equivalence point besides titration curve (said indicator change color or something), and pH of a weak acid i cant remember but I got approximately 3.57 (can't remember exact number, but 3.5 something) same as a friend. 

But if I'm not mistaken, the question after that, which was Question 8, were enthalpy and entropy calculations, as well as determining the temperature at which a given reaction became spontaneous. 

TZ2 also. 

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7 minutes ago, IB`NOT`ez said:

Yeah I remember there were pH calculations: [H+] of NaOH, pKA = 5, another method to determine equivalence point besides titration curve (said indicator change color or something), and pH of a weak acid i cant remember but I got approximately 3.57 (can't remember exact number, but 3.5 something) same as a friend. 

But if I'm not mistaken, the question after that, which was Question 8, were enthalpy and entropy calculations, as well as determining the temperature at which a given reaction became spontaneous. 

TZ2 also. 

Ah yeaa ic... It's the one with hydrogenation of alkene compound, right?

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1 hour ago, IB`NOT`ez said:

Enthalpy calculations. Do you remember any possible answers? I think for the temperature at which reaction becomes spontaneous was a high number, about 900~ or something. 

 
 

yeah had to find temperature for two questions and both were reallllyyy high... thought was doing something wrong... 

 

tz2 tooo

Edited by IB2017student

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