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OFFICIAL OCR F332 CHEMISTRY B (SALTERS) June 3rd 2014

Reply 60

princess1000

Original post by minibuttons

What did everyone get for the % increase of CO2 produced? I got 26.7% but I think I got it wrong :/

I got 0.8 percent but I think its wrong...

Reply 61

The_Blade

6

Did it ask for % increase or increase in %
?
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Reply 62

The_Blade

6

Original post by cuteincarnate

I THINK the % increase was 0.008%

Please

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Reply 63

cuteincarnate

Original post by The_Blade

Please

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whoaa didn't know you could get the paper this early! :confused:

yeah I got that too
0.030 - 0.038 = 0.008%

I think the wording was designed to catch people out :wink:

I got the same!

Original post by ocelot92

lets start a mark scheme bluds

Mn +4 to +2
I to -1 to 0

reducing agent = iodine, gets oxidised? from -1 to 0 gains in oxidation number

silver nitrate solution

AgCl, white precipitate formed

AgI might have also formed from the ash, so yellow precipitates may also be seen.

reduction = gain of electrons

percentage purity of impure iodine 73.8%

ir spectrum = ethanoic acid as 2500-3200cm-1 (not aldehyde nor ketone)

no absorption corresponding to O-H groups in alcohol so no ethanol present.

carbon monoxide = incomplete combustion

carbon monoxide = toxic, its not a component of photochemical smog is it? (I got this wrong)

CO2 is 3167 times more abundant

bond enthalpy is 285KJmol

high temperatures and high pressures not present in atmosphere so reaction cant go fast

last question = polymers and malolactic acid formation

(all I can remember)

Pretty much what I got.

However I got ethanal and I'm pretty sure it's ethanal. As the OH peak is usually broad for the presence of carboxylic acid so it must've been an aldehyde?

Also I got 78% ish for the impurity question. Don't even know if that's right. The seven marker threw me off though. And the question about observing global warming and some experiments I think... It was a seven marker and I left it blank. Mind went completely blank :frown:

Reply 66

rubi-t

Original post by cuteincarnate

whoaa didn't know you could get the paper this early! :confused:

yeah I got that too
0.030 - 0.038 = 0.008%

I think the wording was designed to catch people out :wink:

I feel stupid now. I got 26.6%

Omg I though the paper went well but I feel silly mistakes coming in already.

Reply 67

Deebernier

Original post by polly_

the ir spec should have been for ethanal, not ethanoic acid as the peak in the 3000 cm-1 range was narrow, not broad as it would have been if it were the O-H in carboxylic acids. The peak at 3000 cm-1 was for C-H bonds in alkanes. In addition, there was another peak around the 1750 cm-1 range, which shows a C=O bond for aldehydes. Carboxylic acids C=O bond would have had a peak closer to 1700 cm-1

There were 2 peaks at 3000, so i assumed one was for C-H and the other was for the O-H of the acid

Reply 68

cuteincarnate

What did anyone get for the molecular formula of retinol reacted with excess bromine? I couldn't work out how many bromine atoms would add across the double bonds :tongue:

Reply 69

JammyGit07

16

Original post by cuteincarnate

What did anyone get for the molecular formula of retinol reacted with excess bromine? I couldn't work out how many bromine atoms would add across the double bonds :tongue:

2 for each double bond, and there was 5 double bonds :smile:

Reply 70

cuteincarnate

Original post by ocelot92

lets start a mark scheme bluds

Mn +4 to +2
I to -1 to 0

reducing agent = iodine, gets oxidised? from -1 to 0 gains in oxidation number

silver nitrate solution

AgCl, white precipitate formed

AgI might have also formed from the ash, so yellow precipitates may also be seen.

reduction = gain of electrons

percentage purity of impure iodine 73.8%

ir spectrum = ethanoic acid as 2500-3200cm-1 (not aldehyde nor ketone)

no absorption corresponding to O-H groups in alcohol so no ethanol present.

carbon monoxide = incomplete combustion

carbon monoxide = toxic, its not a component of photochemical smog is it? (I got this wrong)

CO2 is 3167 times more abundant

bond enthalpy is 285KJmol

high temperatures and high pressures not present in atmosphere so reaction cant go fast

last question = polymers and malolactic acid formation

(all I can remember)

ahh I think you have to say "CO comes from incomplete combustion of HYDROCARBONS in a car engine" (I remember a past paper not letting you have the mark unless you talked about hydrocarbons)

I did the same thing about photochemical smog!! going to go and look it up now

Reply 71

ocelot92

7

Original post by cuteincarnate

What did anyone get for the molecular formula of retinol reacted with excess bromine? I couldn't work out how many bromine atoms would add across the double bonds :tongue:

5 double bonds so 5 molecules of Br2. so the formula was the molecular formula at the start with Br10

Reply 72

ocelot92

7

Original post by cuteincarnate

ahh I think you have to say "CO comes from incomplete combustion of HYDROCARBONS in a car engine" (I remember a past paper not letting you have the mark unless you talked about hydrocarbons)

I did the same thing about photochemical smog!! going to go and look it up now

about hydrocarbons i said that lol. luckily ahhahaha but said 'hydrocarbon fuels'.

yeah photochemical smog was incorrect i think

Reply 73

JammyGit07

16

Original post by ocelot92

about hydrocarbons i said that lol. luckily ahhahaha but said 'hydrocarbon fuels'.

yeah photochemical smog was incorrect i think

I think they were looking for the fact its a toxic gas as well as a greenhouse gas :/

Reply 74

cuteincarnate

Original post by ocelot92

lets start a mark scheme bluds

Mn +4 to +2
I to -1 to 0

reducing agent = iodine, gets oxidised? from -1 to 0 gains in oxidation number

silver nitrate solution

AgCl, white precipitate formed

AgI might have also formed from the ash, so yellow precipitates may also be seen.

reduction = gain of electrons

percentage purity of impure iodine 73.8%

ir spectrum = ethanoic acid as 2500-3200cm-1 (not aldehyde nor ketone)

no absorption corresponding to O-H groups in alcohol so no ethanol present.

carbon monoxide = incomplete combustion

carbon monoxide = toxic, its not a component of photochemical smog is it? (I got this wrong)

CO2 is 3167 times more abundant

bond enthalpy is 285KJmol

high temperatures and high pressures not present in atmosphere so reaction cant go fast

last question = polymers and malolactic acid formation

(all I can remember)

http://www.sciensage.info/journal/1359642715JASR_2609111.pdf

CO is a component of photochemical smog (as above). I don't know if OCR will have it on their markschemes though! :tongue:

Reply 75

cuteincarnate

Original post by ocelot92

5 double bonds so 5 molecules of Br2. so the formula was the molecular formula at the start with Br10

So you don't think the CH3 groups would have an effect? pahaha of course not, sounds so stupid now :tongue:

Reply 76

tealover96

15

Please someone clarify this for me...for the IR questions ethanal or ethanoic acid?
Again after writing down both answers and much debating I chose ethanal

Reply 77

carrotstar

21

Thought that was a pretty nice exam really! There were loads of past paper questions in there. Unfortunately that means grade boundaries will be pretty high...

Original post by HappyHumanist

I actually thought that was quite easy compared to other past papers, hope it went well for everyone else. Messed up the spectroscopy one by putting ethanone instead of ethanal grrr. For the 7 marker it was hydrogen bonds and VDW's right?

I did hydrogen bonds and ID-ID. What are VDW's? Not heard that abbreviation before? And yeah, same about past paper comparison!

Original post by RhinoBiker

Finally a nice paper! Could answer everything, but it's all about the wording at the end of the day...

Agree! There's loads of words and images buzzing around in my head, and then I have to put them into some kind of legible order...

Original post by minibuttons

I thought for OH in carboxylic acids the range is 2500-3200 cm^-1 and there was a peak around 3000. Oh no :/
Yeh I put hydrogen bonds for propanone and ethanol. I was confused for the second one and put permanent dipole-permanent dipole for some reason - I know I got it wrong though.

I put ethanoic acid because, yes, there was a peak at around 3000.

Original post by JammyGit07

Whats people's grade boundaries predictions?

I think they'll be pretty high! I haven't seen a past paper that easy for a couple of years, and the last few have been around 68-70 for an A. I reckon this one will be at least 75, maybe even 80! So a B at around 74, C at around 62, D at around 53 etc...

Reply 78

cuteincarnate

Original post by tealover96

Please someone clarify this for me...for the IR questions ethanal or ethanoic acid?
Again after writing down both answers and much debating I chose ethanal