Edexcel IAL Chemistry Units4&amp;5

Original post by Chandru4

No its actually Oxygen. It says so in my textbook.

Just checked my book. It's definitely CO2.

Reply 61

Original post by anonymous199

did the food crop advantage disadvantage question ask for alternative fuels?

No?

We had to compare the disadvantages and advantages of biofuel obtained from samphire and oil obtained from non-edible seeds and just pick which one we thought would be greener/more sustainable. Then we had to justify why we picked it.

From what I've seen in past papers, they'll usually allow choosing either fuel as long as you have a sound and sensible justification for it.

Reply 62

Chandru4

1

Original post by thymolphthalein

My notes say that in the mobile phase of gas chromatography you can use nitrogen, helium, argon, carbon dioxide etc. Sooo idk.

Edit: I googled and found this. http://teaching.shu.ac.uk/hwb/chemistry/tutorials/chrom/gaschrm.htm along with a bunch of other pages on the use of carbon dioxide being used in gas chromatography.

Reply 63

Original post by Chandru4

Oxygen is really reactive though and CO2 is a much less reactive molecule.

Ah, well. I still stick to CO2. Guess we'll see. :biggrin:

Reply 64

AhmedBilal

Is it just me or did everyone struggle with the biodiesel question?
I feel like i didn't get a single part correct in that question.
Will the grade boundaries be lower than normal?

Reply 65

Hahah, I feel like I'm the only one who is ever prepared for Green Chemistry questions. :tongue:

Grade boundaries should be lower than January, I think. A lot of people didn't find the paper hard but many didn't finish it, due to all the Data Booklet searches we had to do and what not. The questions were quite long too.

But seeing as it's Edexcel Chemistry, I would not be too optimistic about grade boundaries decreasing significantly.

Reply 66

kor97

1

Sort of assuming everyone's done now. This is the little that I remember of the paper. Hopefully everyone can add stuff to it.

MCQ: mostly okay. I remember for gas chromatography, I chose CO2 (most inert from the list) but wasn't sure. One of the units was atm^4.

Acid/base question: buffer solution with ammonia and ammonium ions, equivalence point is less than 7 because ammonium ions are the conjugate acid of the weak base ammonia, can't remember exact numbers but ph was 1.something?, ph of water was 6.something as well but neutral

rates question: 0 order wrt A, 2nd order wrt B, 1 order wrt X, k was 40mol^-2dm^6s^-1

dodec question: ethyl dodecanoate, reducing agent, why was temperature low?

biodiesel/seed question: distillation, catalyst was NaOH, advantages and disadvantages

entropy/enthalpy question: had to look up enthalpy of formations and work out enthalpy of reaction (large negative), entropy of system (negative), entropy of surroundings (large positive) and total entropy change (positive), effect of increasing temperature on entropy and yield, nmr question at the end, area is 3, septet (7)

Reply 67

Original post by AhmedBilal

Is it just me or did everyone struggle with the biodiesel question?
I feel like i didn't get a single part correct in that question.
Will the grade boundaries be lower than normal?

I dont think that it was that hard. I think it was just really different so now no one knows whether its right or wrong.

In the first question, i think in part b or c, they ask for an ionic equation. What did you all write?

Reply 68

Original post by Trixenity

I dont think that it was that hard. I think it was just really different so now no one knows whether its right or wrong.

In the first question, i think in part b or c, they ask for an ionic equation. What did you all write?

Well according to my notes you can write:

Salt formed from NH3 and HCl hydrolyzes as:

NH4+ + H2O ---> NH3 + H3O+

If H3O+ concentration increases, the pH decreases and it's less than 7.

I wrote that but messed up my equation. :facepalm:

Reply 69

Original post by kor97

Sort of assuming everyone's done now. This is the little that I remember of the paper. Hopefully everyone can add stuff to it.

MCQ: mostly okay. I remember for gas chromatography, I chose CO2 (most inert from the list) but wasn't sure. One of the units was atm^4.

Acid/base question: buffer solution with ammonia and ammonium ions, equivalence point is less than 7 because ammonium ions are the conjugate acid of the weak base ammonia, can't remember exact numbers but ph was 1.something?, ph of water was 6.something as well but neutral

rates question: 0 order wrt A, 2nd order wrt B, 1 order wrt X, k was 40mol^-2dm^6s^-1

dodec question: ethyl dodecanoate, reducing agent, why was temperature low?

biodiesel/seed question: distillation, catalyst was NaOH, advantages and disadvantages

entropy/enthalpy question: had to look up enthalpy of formations and work out enthalpy of reaction (large negative), entropy of system (negative), entropy of surroundings (large positive) and total entropy change (positive), effect of increasing temperature on entropy and yield, nmr question at the end, area is 3, septet (7)

Yes, to the MCQs. :biggrin:

Acid base also correct. They gave the pH for the water anyway, we just had to show it, didn't we?
For some reason, I decided to write 'can be described as acidic because H+ concentration is greater than OH- concentration at that specific temperature', I'm not sure if they'll explain it although what I meant was that it is effectively neutral. Just at that temperature dissociation is towards more H+ ions causing the neutral point to change? I write stupid things even when I understand the concept haha.

Yes, to the rates too and the ester question. I think probably because it's an exothermic reaction or because that's how you get a maximum yield.

Biodiesel is correct as well.

Can't remember my enthalpy values but the signs match up. And yes, it was a septet, I got the area wrong though.

Reply 70

I wrote NH3 + H2O -> NH4 + OH- and that the pH is below seven because of the NH4+. I dont think its right now :/

Reply 71

Original post by Trixenity

I wrote NH3 + H2O -> NH4 + OH- and that the pH is below seven because of the NH4+. I dont think its right now :/

OH- would increase the pH.

You're supposed to write H+ or H3O+ if it's less than 7 (i.e. slightly more acidic than basic)

Reply 72

Original post by thymolphthalein

OH- would increase the pH.

You're supposed to write H+ or H3O+ if it's less than 7 (i.e. slightly more acidic than basic)

The OH- would be neutralized by the acid, so at the equivalence point only NH4+ would remain. But thats if my equation is right.

Reply 73

dhrumitvora

was ph 1.62

and mcq for cn quesn was it hcl

and why the rate wasnt the same....not a closed system...and...temp not kept constant

and can u use change in mass measurement for the rate using digital balance and a collection of gas using a test tube

delta s total was 6000 smfin and s system was -860 and s surr was 7000 smfin

then why was it suitable to add another value to the table? didnt know dat jus wrote to have a more accurate value of data

Reply 74

dhrumitvora

advantages

renewable and no pollution is caused

disad takes a long time and alot of land

didnt know wich was greener though lol so jus left it

Reply 75