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F334 (19/06/2013 9:00AM) - Salters Chemistry (Chemistry of Materials) Revision Thread

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I wasn't sure about that as well... It gave the volume reading of NaOH to 4 sig figs and the rest to 3 sig figs... So I'm not too sure whether it would be 1.695 or 1.70..

The appropriate number is the lower number given in the question

so it was 1.69g

Reply 321

Mangodepo11

Original post by aWildPidgey

But h2o wasn't in the rate determining step even though it was in the rate equation

I thought that if it was in the rate equation it was in the rate determining step

Yh I know thats why I got super confused and changed my order of water from 2 to 0. As if water isn't in the slow step it can't be in the rate equation? Maybe it's something to do with the intermediates formed from water.

Reply 322

MTI

Original post by abzy1234

Don't worry, I'm sure you'll pick up marks elsewhere :smile:

Exactly, no point worrying about what's done tbh. If anything it's time to celebrate that chemistry is all over! :biggrin:

haha yes but im hopefully studying chemistry at uni come October, i love chemistry! :L but its definitely time to celebrate end of exams!!! :biggrin:

Reply 323

abzy1234

Original post by aWildPidgey

The appropriate number is the lower number given in the question

so it was 1.69g

Ah awesome, 1.69 it is then! One of the first times salters TSR agree on a calculation question :biggrin:

Reply 324

abzy1234

Original post by MTI

haha yes but im hopefully studying chemistry at uni come October, i love chemistry! :L but its definitely time to celebrate end of exams!!! :biggrin:

Oh at least you'll be freed from the restrictions of salters chemistry! :biggrin:

After 2 painful years, celebration is well worth it :tongue:

Reply 325

Another

Original post by abzy1234

But wasn't the volume of NaOH to 4 sig figs.. that's what made me a bit wary to giving it to 3sf :tongue:

Wait, it was? Completely did not even notice that. Miracle I even got the right answer!

Well, if this comes back as an A, this paper would have been a miracle in itself.

Reply 326

aWildPidgey

Let's do a markscheme

Everyone add to the list of QUESTIONS below

1a - i have no ******* idea, someone will have to remember

Reply 327

abzy1234

Original post by Another

Wait, it was? Completely did not even notice that. Miracle I even got the right answer!

Well, if this comes back as an A, this paper would have been a miracle in itself.

I think it was, but as someone said, you do give it to the lowest sf, so 1.69 it is :biggrin:

hope we get that A :smile:

Reply 328

Another

Original post by aWildPidgey

Let's do a markscheme

Everyone add to the list of QUESTIONS below

1a - i have no ******* idea, someone will have to remember

That was circle the ester link. I'm not too sure though - I circled the COO bond and nothing else. Anything after that, I cant remember a thing :biggrin:

Reply 329

EdwinLo

Heat under reflux with acidified potassium dichromate and distil off in situ as the reaction progresses.

Reply 330

aWildPidgey

This seemed like a really easy paper at first and now I think we'll all have made a few silly mistakes...

which is good for grade boundaries

Reply 331

Pucilowski

Was the zwitterion overall basic or neutral? I spent a while debating whether the phenol will dissociate in water and in the end decided that it won't and the molecule will remain neutral. I then argued in the following question because there's a balance of charge the pH remains neutral.

If I got the first part wrong (zwitterion was in fact basic) will I get e.c.f on the following question?

Reply 332

EdwinLo

Original post by Pucilowski

Wait so in the zwitterion does the phenol OH group become O-? Really unsure about this as that is what I put and I'm not sure if it's right.

Reply 333

Pucilowski

Original post by EdwinLo

Wait so in the zwitterion does the phenol OH group become O-? Really unsure about this as that is what I put and I'm not sure if it's right.

This is my question. Whether the phenol groups dissociates or not determines whether the zwitterion ends up basic or neutral. I think it does indeed dissociate and the overall charge ends up being 1- so it is alkali.

Question is, will I get e.c.f on my explanation in the next question.

Reply 334

Mattywooda

Original post by EdwinLo

Wait so in the zwitterion does the phenol OH group become O-? Really unsure about this as that is what I put and I'm not sure if it's right.

Yeah, phenols react with NaOH. Think it was acidic due to the phenol

Reply 335

Mattywooda

Original post by aWildPidgey

But h2o wasn't in the rate determining step even though it was in the rate equation

I thought that if it was in the rate equation it was in the rate determining step

Original post by Richyp22

You require 2H2O to give the one OH in the rate determining step, so it made sense water was to the order 2, because effectively you were using two waters.

Reply 336

EdwinLo

Original post by Mattywooda

Yeah, phenols react with NaOH. Think it was acidic due to the phenol

No but I mean in the previous question where it is in water does the phenol OH become O-? Or am I remembering the questions wrongly...what was the question where you had to draw the zwitterion?

Reply 337

DoeADeer

So you can only lose 18 marks to get an A?! For chemistry, I think that's ridiculous.

Reply 338

EdwinLo

Original post by DoeADeer

So you can only lose 18 marks to get an A?! For chemistry, I think that's ridiculous.

Well it depends, 72/90 is often 90 UMS and A is like mid 60s so you can lose more than that generally and still get an A.

Reply 339

Mattywooda

Original post by EdwinLo

No but I mean in the previous question where it is in water does the phenol OH become O-? Or am I remembering the questions wrongly...what was the question where you had to draw the zwitterion?