Advanced Higher Chemistry 2012-2013

Original post by FeelingofSuccess

Ah, stupid me! Any idea how many marks I'd lose for this (out of 3)?
Thanks :smile:

It's hard to say.

If the marking scheme lets you use n=6 then to divide by 2 and you have the correct units to get three marks, you'd probably get 2/3.

If the marking scheme stipulates you must use n=3, probably 0 or 1. However I think the first method is equally as valid (that's what I'd do), so as long as your units were correct I'd say 2/3. Not a guarantee though.

EDIT: I'm going to say that you might get 1.5/3 for the first method as you also didn't get the correct answer.

(edited 10 years ago)

Reply 1982

Original post by Zahra Tasleen

If you 8aii NaOH I wrote 0 would I get penalised again for c and cause my answer was wrong or do u get consecentuial marks

Posted from TSR Mobile

It was 0 order w.r.t NaOH though.

Reply 1983

Original post by GermanScientist

What did you have as the GFM?

divided 0.942/116 = 0.008 moles

And since 1 Ni ----> 2 C4H8O2N2

Ni moles = 0.004

m= n x g = 0.2348g

% = 0.2348/0.968 x 100
= 24.3%

Reply 1984

Original post by GermanScientist

It was 0 order w.r.t NaOH though.

I put 1 for that and as a result i got

b) rate=k(C4H9Br)(NaOH)
c) k= 1875mol l-1 s-1

would i get full marks for those as it's a follow through error?

Reply 1985

fragle

1

I'm a chemistry tutor (I used to answer lots of questions on here in the past, but have been away from the site for quite a while) and I have just had a quick look through the paper. I think part A was pretty hard especially the unit 1 and 2 stuff (not too many examples of that stuff in the past papers). Also a few 'trick' questions thrown in like the benzene to cyclohexane one, we spend so much time drumming into students in that benzene undergoes substitution reactions- and then they throw in an addition. However, I thought that section B was quite straightforward as long as you had the PPAs learned - not sure my students did, even though they were told too many time :rolleyes:

Reply 1986

FeelingofSuccess

Original post by GermanScientist

It's hard to say.

If the marking scheme lets you use n=6 then to divide by 2 and you have the correct units to get three marks, you'd probably get 2/3.

If the marking scheme stipulates you must use n=3, probably 0 or 1. However I think the first method is equally as valid (that's what I'd do), so as long as your units were correct I'd say 2/3. Not a guarantee though.

EDIT: I'm going to say that you might get 1.5/3 for the first method as you also didn't get the correct answer.

Okay thanks a lot! :smile:

Quite happy overall as I am pretty sure I got an A :smile:

Reply 1987

kirstyhr

Looking over answers etc I don't think I've done as badly as I originally thought I had! Phew! Thanks to everyone who's been posting solutions :smile:

Reply 1988

Original post by n00b/

I put 1 for that and as a result i got

b) rate=k(C4H9Br)(NaOH)
c) k= 1875mol l-1 s-1

would i get full marks for those as it's a follow through error?

Probably not as your units are incorrect for a reaction of order 2.

Reply 1989

MOHSINM31

OMG!! I read the word dehydrating agent as drying agent also! FML!!!

Posted from TSR Mobile

Reply 1990

Asklepios

19

Original post by MOHSINM31

OMG!! I read the word dehydrating agent as drying agent also! FML!!!

Posted from TSR Mobile

If they wrote dehydrating reagent I reckon I would have been fine

Reply 1991

Original post by GermanScientist

Probably not as your units are incorrect for a reaction of order 2.

probably 1/1 for b
& 1/2 for c

Reply 1992

Original post by n00b/

divided 0.942/116 = 0.008 moles

And since 1 Ni ----> 2 C4H8O2N2

Ni moles = 0.004

m= n x g = 0.2348g

% = 0.2348/0.968 x 100
= 24.3%

I don't think you factored in the 7H₂O, did you?

Hmm it's hard to say. 1 at the max, but I would say maybe a half-mark for working out the percentage. I can't remember if they're allowed to give half marks though. But I think there's roughly be 4 points here, so 4 half-marks to be gained:

•

Calculate the moles of the complex

•

Knowing it's a 1 mole to 1 mole ratio

•

Working out the mass of nickel in the sample

•

Calculating the percentage by mass

Reply 1993

Original post by n00b/

probably 1/1 for b
& 1/2 for c

It'd be 0 for (b) I'm afraid. It's one mark for the rate equation, or 0 for a wrong one.

For (c) I think it could be 1 mark out of the possible 2. You carried on with your mistake but your units were, unfortunately, incorrect.

Reply 1994

deedee123

16

Original post by Asklepios

What did you put for the empirical formula?

like CH6O or something

im sitting on about 62-63% so as long as i get at least 8/25 in my report i should get a B which is what i need :bl:

(edited 10 years ago)

Reply 1995

Original post by kirstyhr

Looking over answers etc I don't think I've done as badly as I originally thought I had! Phew! Thanks to everyone who's been posting solutions :smile:

Glad to hear it! :biggrin:

Reply 1996

Original post by GermanScientist

I don't think you factored in the 7H₂O, did you?

Hmm it's hard to say. 1 at the max, but I would say maybe a half-mark for working out the percentage. I can't remember if they're allowed to give half marks though. But I think there's roughly be 4 points here, so 4 half-marks to be gained:

•

Calculate the moles of the complex

•

Knowing it's a 1 mole to 1 mole ratio

•

Working out the mass of nickel in the sample

•

Calculating the percentage by mass

Nope, just hope I get a slightly generous marker.

Reply 1997

Original post by GermanScientist

It'd be 0 for (b) I'm afraid. It's one mark for the rate equation, or 0 for a wrong one.

For (c) I think it could be 1 mark out of the possible 2. You carried on with your mistake but your units were, unfortunately, incorrect.

Yes but using my answers to part a led me to get the rate equation of

rate=k(NaOH)(C4H9Br)

surely they wouldn't penalise me for part b if i already lost the mark in part a

Reply 1998

Original post by n00b/

Nope, just hope I get a slightly generous marker.

Contrary to what some people believe, markers actually want to give marks as opposed to deducting them, so I wouldn't worry about it too much :tongue:

Reply 1999