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OCR F324-June 2013 Chemistry

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It doesn't depend on the ruler, but the accuracy of measurement (assuming rulers are pretty standard). You'll get one mark for clear working, but I don't know how lenient they'll be on the actual value.

Phenylethene.

I got 0.53 ? I think its acceptable and they will give a range of answer as it said approx! I choose methionine

Reply 3521

Onkar-M

Guys were the monomers a diol and dicarboxylic acid?

Reply 3522

Lehal

what did people get for % yield? wasn't it 69.1%?

Reply 3523

überambitious_ox

Original post by Joel R

No, sorry, since the salt was NH3+ Cl-; the Cl was important.

That wasn't a diazotisation reaction, that was an amine reacting with an acid to form a salt, and hydrochloric acid was needed because the structure was nh3+cl-.

Edit:

I'm sorry, I have quoted the wrong person.

(edited 10 years ago)

Reply 3524

überambitious_ox

Original post by Varsh05

Guys,for this question:
* The flowchart below shows some reactions of 4-aminophenol. (Flowchart showing 4-aminophenol forming its ammonium salt in reaction I, forming 4-amino-3,5-dibromophenol in reaction II, and reacting with Na in reaction III).

* Identity (typo in paper) the reagent in reaction I. (1)

* HCl

Instead of HCl,I put HNO2.
Is that still correct??

No as it wasn't a diazotisation reaction at this stage. It was just an amine acting as a base, reacting with an acid, which was HCl.

Reply 3525

MathsNerd1

Original post by otrivine

I got 0.53 ? I think its acceptable and they will give a range of answer as it said approx! I choose methionine

Surely you've been taught to measure from the middle of the dot? That sounds too low to still be accepted I believe :-/

Reply 3526

Mus1995

Original post by nothepreacher

55 for full ums? I thought it would be 59 or 60. People on here are saying it should drawn in 3d? Also were there 2 chiral centres?

Two chiral centres. I flipped the top one.

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Reply 3527

Mus1995

Original post by MathsNerd1

Surely you've been taught to measure from the middle of the dot? That sounds too low to still be accepted I believe :-/

I measured from the middle to get 0.54447...

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Reply 3528

MathsNerd1

Original post by Mus1995

I measured from the middle to get 0.54447...

Posted from TSR Mobile

I measured from the centre and got 2.7/4.7 so got the answer of 0.57 something which was close enough to the answer

Reply 3529

otrivine

Original post by MathsNerd1

Surely you've been taught to measure from the middle of the dot? That sounds too low to still be accepted I believe :-/

Yep I did it correct, the question said approximation.

depends on the ruler and scale

Reply 3530

otrivine

Original post by MathsNerd1

I measured from the centre and got 2.7/4.7 so got the answer of 0.57 something which was close enough to the answer

thats wrong you dont measure from the middle, you measure from the line to the bottom of the dot, not the middle, difficult to explain but see the page in the book

Reply 3531

MathsNerd1

Original post by otrivine

thats wrong you dont measure from the middle, you measure from the line to the bottom of the dot, not the middle, difficult to explain but see the page in the book

I've always been told this way for them all and would make a more accurate prediction in this case, I'll still get the marks as I got it right

Reply 3532

otrivine

Original post by Mus1995

I measured from the middle to get 0.54447...

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I got the same, but the book measures it from the bottom not middle?

Reply 3533

otrivine

Original post by MathsNerd1

I've always been told this way for them all and would make a more accurate prediction in this case, I'll still get the marks as I got it right

yes, if you would have measured it from the bottom like the book you should get a value around 0.53 to 0.55

Reply 3534

Joel R

Original post by Lehal

what did people get for % yield? wasn't it 69.1%?

No. Did you just divide the mass of G obtained by the mass of E given? I believe that gives around 69%.

The correct method was to divide the mass of E by its Mr (160) to get the number of moles. You then multiply this by the Mr of G (174) to get the maximum possible mass of G obtainable (which is greater than the mass of E used, since other reactants are 'put in' to get G), and divide the mass of G given in the question (3.something) by this mass, and times by 100 to get percentage yield.

(edited 10 years ago)

Reply 3535

Mus1995

Original post by otrivine

yes, if you would have measured it from the bottom like the book you should get a value around 0.53 to 0.55

I did 0.27/0.47. 0.57444 which is around 0.58.

0.53-0.55 is way off. I don't think it would be correct.

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Reply 3536

Zaphod77

Original post by MathsNerd1

I measured from the centre and got 2.7/4.7 so got the answer of 0.57 something which was close enough to the answer

That's exactly what I got! (the 2.7/4.7) :smile:

Reply 3537

otrivine

Original post by Mus1995

I did 0.27/0.47. 0.57444 which is around 0.58.

0.53-0.55 is way off. I don't think it would be correct.

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Check page 79, they dont do it from the centre, they did it from the dotted line to the bottom of the dot , i did exactly like that, not to centre

Reply 3538

MathsNerd1

Original post by Zaphod77

That's exactly what I got! (the 2.7/4.7) :smile:

Very nice! :biggrin:

Reply 3539

nothepreacher

Original post by Mus1995

Two chiral centres. I flipped the top one.

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Thanks for answering. So the bottom one was kept at the centre right? Also, in my diag there was only only one wedge from my chiral centre, the rest were skeletal lines