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HL Chemistry paper 1 and 2

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SOOOO I answered numbers 7 and 10 in Section B... annnnd I didn't solve the last page (from number 10) because I didn't see it.. Great.  :mellow::angry:


So, how was the Chemistry paper. I was in TZ2 I think, and the paper 1 was quite hard to be honest

Let's hope the grade boundaries go low this year :P 

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Im in TZ1
Generally my classmates and i thought paper 1 was ok. There was no tricky electrolysis questions in MCQ, which are very prone to errors of misreading *oxidizing/reducing agent, oxidized/reduced species, cathodes/anodes*. I think that was definitely helpful to those who are(were) taking the course in a second language. (eletrolysis specifics were asked in question 6 in Part B P2)
A MC question on making buffer solutions ... i anticipated choices of conjugate acid/base pairs but all four choices were either ammonia with HCl, ammonia with KCl, strong acid/base, (and one more i forgot). A question about dissociation of water when temperature is above STP; Questions mostly straight forward. Some are tricky but with clear wording in the question and answers. 

Paper 2
the data question threw a lot of people of (myself included). it was on finding number of water ligands on (COOH)2 after titration. in the scaffolding process, it asked for mol of HCl (from data). Mass of (COOH)2 to make the stock solution was given. 1/10th (25mL out of 250mL) were transferred to a beaker for titration for 3 trials. Equation of (COOH)2 reaction with HCl is stated, but without the ligands. Question eventually asked for molar mass of compound (1 mark) then to find # of ligands/molecule (2 marks). I just made up a molar mass and got to 6 ligands. 

I thought something like small details mentioned in the syllabus that some schools might gloss over were included in section A and they did show up: reaction of water and phosphorus (V) oxide (P4O10). Lot of people put P2O5. Definitely one just by memorization. In class we talked about acidity and chloride and oxides but not a lot of depth went into remember the equations.

3 of the 4 Part B questions had organic chem and enthalpy. IB's definitely looking to prevent people from avoiding any units completely, though not lot of mechanism were asked throughout the paper. (and when they did, explicitly demanding an elimination, i put an SN2 mech for some unknown reason).

An interesting question in Question 5 when asked to calculate enthalpy of formation of propanoic acid given its enthalpy of combustion and table 15. Apparently we were suppose to find enthalpy of combustion of CO, which makes a single CO2 and H2O, exactly 1/3rd the products of that of propanoic acid (or was it propan-1-ol, i can't quite recollect).

Also, balancing oxidising of primary alcohol to aldehyde (with [O] = Cr2O7(2-) is A LOT more complicated than balance one to carboxylic acid.

The last page of the P2 exam had questions on it, which might have been unexpected and missed.

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I'm TZ2 and I think P1 was a bit tough. There were some really tricky questions. P2 went quite well. Questions 7 and 10 in Section B were fairly straightforward. 

Everyone I know did question 7. 

XD

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SOOOO I answered numbers 7 and 10 in Section B... annnnd I didn't solve the last page (from number 10) because I didn't see it.. Great.  :mellow::angry:

So, how was the Chemistry paper. I was in TZ2 I think, and the paper 1 was quite hard to be honest

Let's hope the grade boundaries go low this year :P

 

HAHAHAHA. I did the exact same thing and I thought I was the only one! I don't know how but I never saw that last page!! 1 minute before time was called, I flipped the page and saw that freaking 5 marker! I managed to scribble the diagram for cis and trans but-2-ene but lost the other 3 marks :(

 

I did question number 8 and 10 in Section B TZ2, Because I did not dare to attempt those 7-8 marks of Acids and bases questions from Question 7. 

 

I found a lot of the questions in No. 8 very vague and rather stupid. Like Cr2O3 formation or whatever it was asking for. Also, what did you guys write for why aluminium is used instead of Iron?? I wrote its a better reducing agent :/ hope that's right :/ . 

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Paper 1 was WAY WAY harder than last years paper. I got a 39 on 40 on practicing last year's paper because the questions were too damn easy. But Paper 1 TZ2 had at least 10 time-consuming and tricky questions. 

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SOOOO I answered numbers 7 and 10 in Section B... annnnd I didn't solve the last page (from number 10) because I didn't see it.. Great.  :mellow::angry:

So, how was the Chemistry paper. I was in TZ2 I think, and the paper 1 was quite hard to be honest

Let's hope the grade boundaries go low this year :P

 

HAHAHAHA. I did the exact same thing and I thought I was the only one! I don't know how but I never saw that last page!! 1 minute before time was called, I flipped the page and saw that freaking 5 marker! I managed to scribble the diagram for cis and trans but-2-ene but lost the other 3 marks :(

 

I did question number 8 and 10 in Section B TZ2, Because I did not dare to attempt those 7-8 marks of Acids and bases questions from Question 7. 

 

I found a lot of the questions in No. 8 very vague and rather stupid. Like Cr2O3 formation or whatever it was asking for. Also, what did you guys write for why aluminium is used instead of Iron?? I wrote its a better reducing agent :/ hope that's right :/ . 

 

Ah screw it :P I saw it the second I was handing my paper in........ I HAVE NO CLUE HOW I DIDN'T SEE IT. I literally had a mini heart attack when I saw it. Yo, didn't number 7 also have something to do with equilibrium and I think a short one on electrolysis or whatever

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I did TZ1, everyone thought P1 very hard and then P2 was hard but not too bad, Q10 saved me seriously and Q7 was good too so I'm just gonna be hoping for low grade boundaries

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What I was a bit disappointed about is that i spent so long learning organic chemistry reaction pathways and then there were only like two or three questions overall in TZ2

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I did TZ2 and tbh Paper 1 i was unsure of some but it wasn't hard. And Paper 2 was a breeze it was so great (except for explaining why engineers would use Aluminium over Iron, i just said its cause Aluminium is the most abundant mineral in the Earth's crust cause it is :P )

 

 

For P1 TZ2, You remember what you guys wrote for that electroylsis question? The one with hydrogen/oxygen something produced at both ends? 

 

I said both produce the same amount of oxygen.


Anyone with answers for the buffer question in section A p2 tz2?

 

Yeah! It was 0.01 mol/dm^3 for the concentration. I used the Henderson-Hasselbalch equation

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I did TZ2 and tbh Paper 1 i was unsure of some but it wasn't hard. And Paper 2 was a breeze it was so great (except for explaining why engineers would use Aluminium over Iron, i just said its cause Aluminium is the most abundant mineral in the Earth's crust cause it is :P )

 

 

For P1 TZ2, You remember what you guys wrote for that electroylsis question? The one with hydrogen/oxygen something produced at both ends? 

 

I said both produce the same amount of oxygen.

Anyone with answers for the buffer question in section A p2 tz2?

 

Yeah! It was 0.01 mol/dm^3 for the concentration. I used the Henderson-Hasselbalch equation

 

Did you take into consideration that the acid in the question is a weak one and thus its Post by: Ruan Chun Xian is not equal to its acid concentration derived from the density value? 

Your answer would be completely correct if it was a strong acid not a weak one. 

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I did TZ2 and tbh Paper 1 i was unsure of some but it wasn't hard. And Paper 2 was a breeze it was so great (except for explaining why engineers would use Aluminium over Iron, i just said its cause Aluminium is the most abundant mineral in the Earth's crust cause it is :P )

 

 

For P1 TZ2, You remember what you guys wrote for that electroylsis question? The one with hydrogen/oxygen something produced at both ends? 

 

I said both produce the same amount of oxygen.

Anyone with answers for the buffer question in section A p2 tz2?

 

Yeah! It was 0.01 mol/dm^3 for the concentration. I used the Henderson-Hasselbalch equation

 

Did you take into consideration that the acid in the question is a weak one and thus its Post by: Ruan Chun Xian is not equal to its acid concentration derived from the density value? 

Your answer would be completely correct if it was a strong acid not a weak one. 

 

 

Um yeah, you can only use Henderson-Hasselbalch with a weak acid buffer haha.

 

So the pH of the buffer was 3.87, and the pKa of the acid was 4.87. The concentration of propanoic acid was 0.1M

 

So pH = pKa + log([salt]/[acid])

3.87 = 4.87 + log([salt]/0.1)

-1 = log([salt]/0.10)

[salt]/0.1 = 0.1

[salt] = 0.01

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I did TZ2 and tbh Paper 1 i was unsure of some but it wasn't hard. And Paper 2 was a breeze it was so great (except for explaining why engineers would use Aluminium over Iron, i just said its cause Aluminium is the most abundant mineral in the Earth's crust cause it is :P )

 

 

For P1 TZ2, You remember what you guys wrote for that electroylsis question? The one with hydrogen/oxygen something produced at both ends? 

 

I said both produce the same amount of oxygen.

Anyone with answers for the buffer question in section A p2 tz2?

 

Yeah! It was 0.01 mol/dm^3 for the concentration. I used the Henderson-Hasselbalch equation

 

 

Isn't quartz the most abundant (silicon and oxygen)? O.o  . I just referred to the data booklet and referred to aluminium's better reducing power relative to Iron :P 

 

YES I wrote the same thing (same amounts of oxygen) produced at both electrodes :D 

 

Urgh I made a stupid mistake in that pH one, but mehh, acids and bases weren't my strong point anyway. What was your answer for the first one? The combined number of protons and neutrons in one H2 molecule? 

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