HL Chemistry paper 1 and 2

[Ossih]

 

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 )

 

 

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

 

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

 

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? 

 

 

You know I thought about it! But that would mean Aluminium is more easily oxidized than Iron and I don't think that's a good thing for engineering :/

 

The first one asked for one H2 molecule? Damn I thought it was one mole of H2 gas so I went with D. But thinking about it, I do remember it saying 1 mol of hydrogen gas, not a molecule  

[Megamind]

Oh wait, it was probably one mol of H2 gas :/ . I probably read it wrong then  

[Megamind]

 

 

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 )

 

 

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

 

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

 

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? 

 

 

You know I thought about it! But that would mean Aluminium is more easily oxidized than Iron and I don't think that's a good thing for engineering :/

 

The first one asked for one H2 molecule? Damn I thought it was one mole of H2 gas so I went with D. But thinking about it, I do remember it saying 1 mol of hydrogen gas, not a molecule

 

 

What did you write for that acid one? Like which substance dissolved in water produces an acidic solution? The only option I remember, which I ticked, was the one with Fe in it. 

[lolatlife]

how much marks do you expect to lose in p2?

[dani_alencar24]

Hey Guys, did TZ2 and thought that Paper 1 was tricky (unsure of some) but answered confidently so I found it OK. Paper 2 was also a breeze, couldn't have asked for a better section A with energetics/Acids and Bases/a bit of electrolysis. (My best and favourite topics   ) Section B was also great, so much so did I did 3 questions because I found them all awesome (7,8,10)   at the end, I couldn't decided which two were the best so I put down 8 and 10 on the cover sheet 

 

Regarding the pH of the buffer, I had completely forgot about the equation and I tried so hard to remember. I was undecisive between pKa + log((salt)/(acid)) = pH and pKa + log((acid)/(salt)) = pH. I chose the first one by luck and also got 0,01 M phew! 

[YAJA]

 

 

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 )

 

 

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

 

Yeah thats true. I did the same exact thing but instead of using 0.1 as acid conc, I calculated the Post by: Ruan Chun Xian from dissociation constant and used it as the acid concentration, 

[Ossih]

 

 

 

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 )

 

 

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

 

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

 

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? 

 

 

You know I thought about it! But that would mean Aluminium is more easily oxidized than Iron and I don't think that's a good thing for engineering :/

 

The first one asked for one H2 molecule? Damn I thought it was one mole of H2 gas so I went with D. But thinking about it, I do remember it saying 1 mol of hydrogen gas, not a molecule

 

 

What did you write for that acid one? Like which substance dissolved in water produces an acidic solution? The only option I remember, which I ticked, was the one with Fe in it. 

 

 

Yeah it was FeCl3 cause of cation hydrolysis  

[dani_alencar24]

Regarding to the aluminium question, I remembered from iGCSE days and said "Aluminium is less dense than iron." Thats why it is used in planes! 

 

With the Paper 1 1st Question, I think you are right that its D because in 1 mole of H2 gas, there are 2 protons and 2 electrons, thus 6x10^23 * 4 2.4x10^24 which was D! I put C instead

Edited May 16, 2015 by dani_alencar24

[medstudent]

I did TZ2. had trouble with the first question in paper 2 but the rest was alright. I hope the grade boundaries are lower this year

[sam1996]

(TZ2) I'm super frustrated with the amount of silly errors I made in paper 2 (not reading the question properly, unit conversions etc.) I hope it won't have cost me a 7. I cannot remember which question this was, probably 9, but we had to work out the bond angle of SF4. I got the shape right but I never learnt or came across bond angles for see saw shapes so I guessed 107. What did you guys get for that?

Edited May 16, 2015 by sam1996

[sam1996]

how much marks do you expect to lose in p2?

Probably 20, plus/minus 3. I made so many stupid mistakes, it still enrages me!!!

[Klauu]

(TZ2) I'm super frustrated with the amount of silly errors I made in paper 2 (not reading the question properly, unit conversions etc.) I hope it won't have cost me a 7. I cannot remember which question this was, probably 9, but we had to work out the bond angle of SF4. I got the shape right but I never learnt or came across bond angles for see saw shapes so I guessed 107. What did you guys get for that?

I said the same thing. 107 for one and <120 and<180 for the other one.both had a lone pair. What did you writr for the question were they asked about the covalent bond between hydrogen and carbon?

[Klauu]

On section A first question what percentage error did you get?

[sam1996]

(TZ2) I'm super frustrated with the amount of silly errors I made in paper 2 (not reading the question properly, unit conversions etc.) I hope it won't have cost me a 7. I cannot remember which question this was, probably 9, but we had to work out the bond angle of SF4. I got the shape right but I never learnt or came across bond angles for see saw shapes so I guessed 107. What did you guys get for that?

I said the same thing. 107 for one and <120 and<180 for the other one.both had a lone pair. What did you writr for the question were they asked about the covalent bond between hydrogen and carbon?

Shared pair of electrons closer attracted to carbon due to its higher electro negativity though I squeezed that last bit in right at the end, may not get the mark. Regarding the percentage error, I got 60 but I used 0.05 not 0.025 mol to work out delta H (the first of my silly mistakes!!) I believe the correct answer is around 20%.

[dorianb]

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

Wasnt it something like the electrolysis of aqueous H2SO4 and CuSO4? I just remember choosing that the same amount of O2 was produced

Edited May 16, 2015 by dorianb

[dorianb]

 

(TZ2) I'm super frustrated with the amount of silly errors I made in paper 2 (not reading the question properly, unit conversions etc.) I hope it won't have cost me a 7. I cannot remember which question this was, probably 9, but we had to work out the bond angle of SF4. I got the shape right but I never learnt or came across bond angles for see saw shapes so I guessed 107. What did you guys get for that?

I said the same thing. 107 for one and <120 and<180 for the other one.both had a lone pair. What did you writr for the question were they asked about the covalent bond between hydrogen and carbon?

 

For the SF4 I wrote see saw, as it has 5 charge centres, 1 non-bonded, and angles of 117, 90 and 180

[dorianb]

 

 

(TZ2) I'm super frustrated with the amount of silly errors I made in paper 2 (not reading the question properly, unit conversions etc.) I hope it won't have cost me a 7. I cannot remember which question this was, probably 9, but we had to work out the bond angle of SF4. I got the shape right but I never learnt or came across bond angles for see saw shapes so I guessed 107. What did you guys get for that?

I said the same thing. 107 for one and <120 and<180 for the other one.both had a lone pair. What did you writr for the question were they asked about the covalent bond between hydrogen and carbon?

Shared pair of electrons closer attracted to carbon due to its higher electro negativity though I squeezed that last bit in right at the end, may not get the mark. Regarding the percentage error, I got 60 but I used 0.05 not 0.025 mol to work out delta H (the first of my silly mistakes!!) I believe the correct answer is around 20%.

 

For the delta T I wrote 6 degrees, which I only noticed the last 5 min. But with that I got 22%, so 20% sounds about right... Hopefully I only lose the one point on the delta T but get the points with ECF

Edited May 16, 2015 by dorianb

[dorianb]

Regarding to the aluminium question, I remembered from iGCSE days and said "Aluminium is less dense than iron." Thats why it is used in planes! 

 

With the Paper 1 1st Question, I think you are right that its D because in 1 mole of H2 gas, there are 2 protons and 2 electrons, thus 6x10^23 * 4 2.4x10^24 which was D! I put C instead

Same here man, thought it was just H, not H2.... Silly mistake

[Klauu]

(TZ2) I'm super frustrated with the amount of silly errors I made in paper 2 (not reading the question properly, unit conversions etc.) I hope it won't have cost me a 7. I cannot remember which question this was, probably 9, but we had to work out the bond angle of SF4. I got the shape right but I never learnt or came across bond angles for see saw shapes so I guessed 107. What did you guys get for that?

I said the same thing. 107 for one and <120 and<180 for the other one.both had a lone pair. What did you writr for the question were they asked about the covalent bond between hydrogen and carbon?

For the SF4 I wrote see saw, as it has 5 charge centres, 1 non-bonded, and angles of 117, 90 and 180

Yeah I wrote see saw too, but I dont know about bond angles some books says its only <120 and <180

[Klauu]

(TZ2) I'm super frustrated with the amount of silly errors I made in paper 2 (not reading the question properly, unit conversions etc.) I hope it won't have cost me a 7. I cannot remember which question this was, probably 9, but we had to work out the bond angle of SF4. I got the shape right but I never learnt or came across bond angles for see saw shapes so I guessed 107. What did you guys get for that?

I said the same thing. 107 for one and <120 and<180 for the other one.both had a lone pair. What did you writr for the question were they asked about the covalent bond between hydrogen and carbon?

Shared pair of electrons closer attracted to carbon due to its higher electro negativity though I squeezed that last bit in right at the end, may not get the mark. Regarding the percentage error, I got 60 but I used 0.05 not 0.025 mol to work out delta H (the first of my silly mistakes!!) I believe the correct answer is around 20%.

Well I wrote that it was dative covalent bond but Im not sure wHy I wrote it