OCR Chemistry B (Salters) F334/F335 Exam Thread 2016 (14th/22nd June)

Original post by hannahstreet_

Why is the oxidation state of vanadium +4 for the first one?

This one was a read the question moment. It says earlier that S2 in of charge 2- s the oxidation state of Sulfur is -1

Reply 161

Original post by baymay

Yh fam its in the spec but tbf there was a question on it in the jan 12 paper i think and the stability explanation was ignored. You were basically supposed to say how carboxylic acid is stronger than the rest because it can react with a strong base and form carbonate.

Isnt it that carboxylic acids can react with Carbonates to produce a salt, carbon dioxide and water? But, say a phenol can't react with a carbonate, so a carboxylic acid is a stronger acid?

Reply 162

samhorton11

6

Guys, there was a lot on storylines last year (genetic fingerprinting, combinatorial chemistry etc) and I think they might ask a lot about storylines again this year. What might they ask?

Reply 163

Tajwar786

just done the 2014 paper and it was such a pain on the backside and the grade boundaries were also high :/ hope they don't do the same this year

Reply 164

josephinemar25

Literally bricking it. I am so nervous, I need to get an A in this exam to even get into my insurance. PLLLLEEAASSSEEE salters give me a nice paper

Reply 165

Thomith

OP

10

Are MnO4- ions pink or purple. Some years i see them accept pink but not purple, other years i see them accept purple but not pink..... dammit salters what the hell?

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Reply 166

baymay

1

Original post by Chloestar

Isnt it that carboxylic acids can react with Carbonates to produce a salt, carbon dioxide and water? But, say a phenol can't react with a carbonate, so a carboxylic acid is a stronger acid?

Yh sorry the only one to react with carbonate and form co2, salt and water

Reply 167

Zuzuvela

Original post by Thomith

Are MnO4- ions pink or purple. Some years i see them accept pink but not purple, other years i see them accept purple but not pink..... dammit salters what the hell?

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They are purple. A permanent pink colour is the endpoint

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Reply 168

Original post by Thomith

Are MnO4- ions pink or purple. Some years i see them accept pink but not purple, other years i see them accept purple but not pink..... dammit salters what the hell?

Posted from TSR Mobile

I thought they were purple but are reduced, so a pink colour persists at the end of a redox titration? I don't know if that's right though!

Reply 169

Thomith

OP

10

Original post by Chloestar

I thought they were purple but are reduced, so a pink colour persists at the end of a redox titration? I don't know if that's right though!

Thats what i thought, but some papers accept what youve written, others accept the opposite, so im not even sure....

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Reply 170

Akantox

Anyone got any predictions for F334?

Reply 171

Tajwar786

Question 2 ei) on june 2014 f334 (IR spectrum)

It clearly tells at top that it reacts with iron (III) Chloride to become purple (SO MUST BE PHENOL)

so I wrote several peaks in range 1450-1650 which indicates arenes of phenol THEY DO NOT ACCEPT THAT THEY want evidence of ester instead why?? >.<

Reply 172

KINGYusuf

12

Does anyone have all the reagents and conditions? Pleaseeeeeeeeeeeeeeeeeeeeeee

Reply 173

Original post by Tajwar786

Question 2 ei) on june 2014 f334 (IR spectrum)

It clearly tells at top that it reacts with iron (III) Chloride to become purple (SO MUST BE PHENOL)

so I wrote several peaks in range 1450-1650 which indicates arenes of phenol THEY DO NOT ACCEPT THAT THEY want evidence of ester instead why?? >.<

I think they want you to mention that the 1742 peak that's indicated must be an ester C=O for one mark.
Then I guess the other noticeable peak to look at would be the broad peak at 3400 which indicates the OH of a phenol.
I'm not sure why they didn't allow the arene peaks, but perhaps they're not definite enough of it being a phenol?

Reply 174

Tajwar786

Original post by Chloestar

I think they want you to mention that the 1742 peak that's indicated must be an ester C=O for one mark.
Then I guess the other noticeable peak to look at would be the broad peak at 3400 which indicates the OH of a phenol.
I'm not sure why they didn't allow the arene peaks, but perhaps they're not definite enough of it being a phenol?

Thank you, I guess sometimes you just have to read the minds of these little **** to answer a question correctly, I also found dozens of examples where slight change in wording gets you no marks (even though they mean the same thing)

there was one where you had to name what is produced in condensation reaction other than organic compound, if you wrote H20 you gain no marks (they want "WATER" explicit) >.<

Reply 175

Ruuth

1

Not sure if someone's already asked this but: what does a higher/lower Tg/Tm even mean? I understand the definitions for Tg and Tm but I keep messing up when I have to apply it to questions. Thanks in advance :smile:

Reply 176