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OCR F324-June 2013 Chemistry

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Hi could someone help me with these two OCR Chemistry F324 questions that i have:

Q1.) When HOCH2CHO reacts with tollens reagent HOCH2COOH is produced not HOOCCOOH. Why ? Is tollens reagent only strong enough to oxidise aldehyde to carboxylic acid not alcohol to carboxylic acid?

Q2.) Propan-1,2,3-triol and C17H31COOH react to produce triglyceride. Deduce the number of carbon double bonds in the molecule of the triglyceride.

Answer is 6. But how is this worked out?

Thanks

Q2) interesting question, C17H31COOH, the COOH takes part in the ester bond so ignore that, then we are left with C17H31, lets say theres a CH3 on the other end of this chain(odd number of hydrogens so must be Ch3 on the end), so now C16H28,if this contains no double bonds then it should be C16H32 but as you can see we are down by 4 hydrogens, which is equal to 2 double bonds being present, then its propan-1,2,3-triol so 3 of these chains. 2x3=6

(edited 10 years ago)

Reply 1241

D4rth

Original post by Sarangtaec

If I used your example of Cl-CH2-CH(CH3)CH2CH3, where did the 5 environments come from? Does the methyl bonded to CH count as the same as the CH3 at the end? And there are 2 CH2s so are they different or the same? I got Carbon environments: C-Cl, -CH2-, CH... and then I'm lost LOL sorry I'm just so confused >_< I'm ok with the splitting patterns though I just hate identifying number of C/H environments -.-

I hope this helps, if not I can't really do much else, it is easier if someone explains it in person. Maybe go see your teacher if you can.

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Reply 1242

Sarangtaec

Original post by D4rth

I hope this helps, if not I can't really do much else, it is easier if someone explains it in person. Maybe go see your teacher if you can.

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Oh my God that's amazing! Hahah thank you so much, I think that's actually helped a lot x) Wow... I get it!

Reply 1243

printergirl

anyone know what the grade boundaries are?
i need about 68 ums, what mark will this be?

i got 36/40 in practicals but what ums is that?

Reply 1244

master y

Original post by printergirl

anyone know what the grade boundaries are?
i need about 68 ums, what mark will this be?

i got 36/40 in practicals but what ums is that?

68ums is about a mid B ish... so around 36/60 ish? for practicals u have 48/60ums =A.

Reply 1245

Sarangtaec

Does anyone know how many UMS points I need for a B if I have 318 points from F321, F322 and F325 so far...? I have no idea how you work that out >_>

Reply 1246

ofudge

Original post by Sarangtaec

Does anyone know how many UMS points I need for a B if I have 318 points from F321, F322 and F325 so far...? I have no idea how you work that out >_>

What did you get in F323 and F326?
You need 450ums overall for a B
So the practicals are each out of 60
And the f324 out of 90
So you need 132 from practicals and f324 from the information you gave

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Reply 1247

Sarangtaec

Original post by ofudge

Whats F323 and F326? We've only done the ones I listed plus practicals which I think I had 50 UMS at AS and I'm not sure but I think 68/100 at A2?

Reply 1248

Gulzar

Original post by Better

I don't do Biology but keep in mind when things get moderated they can get taken down 3-5 marks.

What do you mean moderated?

Reply 1249

Better

Original post by Gulzar

What do you mean moderated?

Your Practicals for Physics/Chemistry and Biology get sent Externally to be assessed by OCR Official Teachers.

They moderate it to see that some schools aren't cheating for examples or Teachers aren't being light with the marking, they usually pick like 3-5 at Random.

If you get chosen you may go down 3-5 marks.

Reply 1250

otrivine

Original post by D4rth

I hope this helps, if not I can't really do much else, it is easier if someone explains it in person. Maybe go see your teacher if you can.

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Really nice explanation there D4rth :smile:

Reply 1251

Gulzar

Original post by Better

Oh God, I heard about that before...is it possible for marks to go up maybe?

Reply 1252

Better

Original post by Gulzar

Oh God, I heard about that before...is it possible for marks to go up maybe?

My Teacher said this generally never ever happens. But anyway chat later. Off to do some Past Papers!

Reply 1253

D4rth

Original post by otrivine

Really nice explanation there D4rth :smile:

Hehe thanks, I feel like I finally know some stuff now, you've been very quiet, want to start revision next week?

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Reply 1254

otrivine

Original post by D4rth

Hehe thanks, I feel like I finally know some stuff now, you've been very quiet, want to start revision next week?

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Yes deffo

you are very good in Chemistry! Just because Biology has been taking most of my time too much content, once I get this done we should start revision by Tuesday :smile:

When is your next exam

Reply 1255

D4rth

Original post by otrivine

Yes deffo

you are very good in Chemistry! Just because Biology has been taking most of my time too much content, once I get this done we should start revision by Tuesday :smile:

When is your next exam

Yea biology is a pain in the ass, takes me 2 days just to get though one topic. My first exams biology on the 17, still got 2 weeks, I just need to finish the last few topics in the subjects then I can kill the past papers and lots of questions over the last week. How do you feel about f324.

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Reply 1256

MathsNerd1

Original post by otrivine

We should start revision by Tuesday :smile:

I'll come and join in after Thursday when I've got my next exam out of the way :biggrin:

Reply 1257

otrivine

Original post by D4rth

I like F324 actually, I enjoy Chemistry is interesting , with proton NMR its all like a jig saw puzzle you have to play around with it to get the correct answer, but I still prefer F325 though after the horrible Jan 2013 paper :eek:

still get the creeps of thinking about that paper

Reply 1258

otrivine

Original post by MathsNerd1

I'll come and join in after Thursday when I've got my next exam out of the way :biggrin:

You are more than welcome :wink:

what is your next exam C3/?

Reply 1259

MathsNerd1

Original post by otrivine

You are more than welcome :wink:

what is your next exam C3/?

Nope, it's M2 then F325, then C3 then C4 the F324 and STEP II on the same day, then FP2 and finally STEP I and AEA also on the same day, should be great fun :tongue: