Equilibria, Energetics and Elements (F325) - January 2012 Exam.

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Reply 640

079

I need 113/150
Not sure if I did well enough anymore!

Reply 641

Bluewinds

Original post by crazy cupcakes

so how exactly would you work it out?

You are told that pH of healthy blood is 7.40 with a 10.5 : 1 ratio of hydro carbonate: carbonic acid and have to find the ratio of blood with a pH of 7.20.

You find the H+ concentration by H+=10^-7.4
You then use the formula - Ka= [H+][HCO3-] divided by [H2CO3]

Inserting the values of H+, 10.5 for HCO3 and 1 for H2CO3 gives the Ka Value. Rearranging the equation gives Ka/H+ = [HCO3-]/[H2CO3]

You put in the Ka value and the H+ value from 10^-7.2, giving the value of [HCO3-] and you put it over 1 to give the ratio.

:biggrin:

Reply 642

crazy cupcakes

Well it looks like im S*****d then :'(

Reply 643

windo

What does every one think the grade boundaries will be? remember we had 15 mins extra and also this was an easier paper than all the previous f325s.

Reply 644

J DOT A

Original post by windo

What does every one think the grade boundaries will be? remember we had 15 mins extra and also this was an easier paper than all the previous f325s.

Probably 77... maybe even in the 80's if only a few people did it and aced it.
Yeah the boundaries will be high. Was far easier than any paper we have done so far.

Reply 645

windo

there was a 4 mark question where u had to write NH3 and Cl ligands around four different complexes. i did it with pencil instead of pen. do i think i will not get the marks cause i did it with pencil. because i looked at it and thought, it did not have the dotted line for writting so it must be for drawing and we can use pencil for drawing. what do u think??

Reply 646

Joseppea

Original post by windo

Well technically they're diagrams...and it says you can use pencil only for diagrams, so they'd have to be incredibly harsh not to mark it! :redface:

Reply 647

windo

What does everybody think the grade boundary for a grade B will be for this paper?

Reply 648

Saliency

Does anyone have a copy of the paper yet?

Reply 649

windo

What does everyone think the grade boundary for a B will be for this paper?

Reply 650

Lemon_Face

for the last one i said about the colour change... that orange and green was easier to see than purple to pink.

and that one with sliver nitrate i said B cos i 2 cl in the mole ratio

think i got like -2506 for the lattice enthlapy

55.8 for the last questons percentage with a 1:6 rato

i got 5 for the kc question

anybody got the same answers as me?????
anybody got the paper? or a mark scheme???
i known it prob too soon for that... :smile:

Reply 651

ab12345

I think alot of people are forgetting that its not just 'clever' people on tsr who sat this paper.
There are other students who probably didn't revise, missed out content, didnt bother or didnt take it seriously and were just relying on June resits.
So grade boundaries may not go into the 80s as some are saying :rolleyes:

Jmo

Reply 652

windo

CAN SOMEBODY PLEEEEASE just gues what the Grade boundary for a grade B will be please??? PLEASE???????

Reply 653

Shadowcake

Original post by windo

CAN SOMEBODY PLEEEEASE just gues what the Grade boundary for a grade B will be please??? PLEASE???????

Personally, i think that it'll be about 65 for a B, as quite a few people felt that it was easier than june 2011. :smile:

Reply 654

Shadowcake

Original post by Lemon_Face

I said the same for the colour change but apparently it was because the Mn2+ reacts with the acid, and it was just something that we had overlooked in the textbook :frown:

I got -2520 or something thereabouts for the lattice enthalpy, add the same as you for the ratio. Cant honestly remember my answers to the rest but i still feel that it went pretty well thankfully. How about you?

Reply 655

Fatima0065

Original post by J DOT A

Probably 77... maybe even in the 80's if only a few people did it and aced it.
Yeah the boundaries will be high. Was far easier than any paper we have done so far.

77 for an A??? !!!! PLEASE CLARIFY..THNKYOU :smile:

Reply 656

Fatima0065

Okai... I was thinking that we could all put the questions that we remember together and then answer them seeing as no1sz got the question paper yet? what do u think?
1st Question was on rates(9 marks) and rate determing step (2 marks)

2nd Question: Born Harber Cycle i think...(dn't kno how much marks it was worht) then the 3 marks question on why it is difficult 2 predict the lattice enthalp of ... , Then it was a 1 mark question but cant remeber it and then a 3 mark question teling you draw the Born harber cycle on MGC03 and how do uo calculate it?

3rd question...anyone??

Reply 657

windo

Original post by Fatima0065

77 for an A??? !!!! PLEASE CLARIFY..THNKYOU :smile:

Hello Fatima0065, do u think 77 for an A is too high? if so what do you think will b the grade boundary for an A and a B will be? :smile:

Reply 658

Fatima0065

Original post by windo

Hello Fatima0065, do u think 77 for an A is too high? if so what do you think will b the grade boundary for an A and a B will be? :smile:

To be honest I reaaly don't know. I'm thinking of asking my techer and then posting reasonable prdicted garde boundaries but I'm still hoping their low despit the extra time we got. It isn't exactly fair if we get high grade boundaries just because we got extar time :0 anywaisz I'm hoping that 73-74 for an A and 67 for a B maybbbeee???? what do you think?