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Equilibria, Energetics and Elements (F325) - June 2011 Exam.

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From the textbook:
"A first order reaction can easily be identified from a concentration time graph. a first order reaction has a constant half life"

The half lives were 190 then 210.

Nowhere in the specification does it say "Half life is constant except sometimes when it's almost constant. It's still first order then."

The half life was increasing. If the mark scheme only gives a mark for first order then that is ridiculous.

I actually got 190 for both half lives so I took it as constant

Reply 2161

Oink123

I need ABB or BBB for my universities. Biology was supposed to be my A and I failed that paper on monday, and Chemistry was meant to be a B but I failed that even harder. Not enjoying this week !

Reply 2162

tophothari

Original post by Sereni

This, though i dont really remember my value for it

Ppl who used lactic acid what was your salt acid ratio?

1 to 1. well at least it is for me as i used NaOH.

Reply 2163

Rickesh

What did everyone write about that stupid buffer question !!! :angry:

Reply 2164

Sereni

Original post by 786girl

yeh but its almostt doubled...since there was a line of best fit i assumed it would be approximate anyway so i said 1st order...argh this paper was REVOLTING

Half life increases with time for second order, and the half life for this question went from 200-190-200-180 so i said assume variation is due to it being experimental data because it definitely didnt INCREASE and so isnt second order, and zero order would be a straight line. Therefore it must be first order

Reply 2165

Unkempt_One

Original post by susan23

half life was constant ..i got 190 first then 200 , then 200 then 200 so I assumed it was 200 (s) and then I got 1st order Br2 and then I just did rate = k[Br2] and subsituted values from the graph to find K... :frown:

thats wrong isnt it???

It shouldn't be. I got k=gradient/0.010

Reply 2166

Dpax2max

Hi everyone as soon as this paper ended my chem teacher took us up to the comp lab- and we all wrote letter of complaint. I know you all think it doesnt work but it does ! I know and the OCR people even told us this year that they you like feeback it is hard for us to know how student found the examm- because they could have really studied hard but not achieved the grades, how much effort a student puts in cant really be determined by their grade" We appreciate any feedback as it could alter grade boundaries-

seriously. I'm not being a brat- I'm a regular B student and I needed a B in this

send to
[email protected]

Reply 2167

LetitiaD

Seriously, wth was that? :'(. I actually felt quite prepared after revising a lot and doing past papers, but no... Bye bye Newcastle...

Reply 2168

ChubbyRain

Original post by Rickesh

Enthalpy of hydration = -2248 ? Or something like that?

I got that but apparantly its wrong because you had to x2 for chlorine :| waaah

Original post by Rickesh

Jan 11 paper was much easier i got 70% in it, shame it was a past paper and doesn't mean anything for me!!!!

I know the past papers were way easier in comparison and still jan 11 was hard! what a joke

Reply 2169

wisefrog

Original post by Sceaga

I said fuel cells and the haber process but that sounds right!

Yay, those were what I put!

Reply 2170

CeliaG593

i completely missed out tangy sweets!! my mind just couldnt work out buffer calculations - which i find really hard anyway - with only the pKa values.
OCR may as well have just punched me in the face and told me to forget going to university!

Reply 2171

Andygunner93

Original post by Flint_09

yes!!!!!!!!!!!!!!!!!!!!!!!!! Thats what i got

I got that too, I also got 45 for an answer to one of the questions, can't remember which one now!

Reply 2172

susan23

Original post by Unkempt_One

It shouldn't be. I got k=gradient/0.010

gradiet at what point?

Reply 2173

mathsmad

This is the second paper by OCR in a week that has just been way of the mark. We need to something about it.
The people who created the group on facebook for biology are telling us to stop moaning on the biology page (rightly so) ... someone make a chemistry facebook page? i dont have facebook (dont trust meself to not speand my life on it^^)
In my opinion... The governments are tied to the exam boards. If we mess up this year and dont get in.. we will be paying the higher tuition fees. So they win.
THIS HAS TO STOP.Anybody with me?

Reply 2174

middle92

**** got
second order, but i think i got the working for the rest right.ECF ECF! drew a tangent to the initial rate then concentration decrease over time?

Reply 2175

KnuckleheadNinja

Original post by anhbui

i hope Hogwarts will still take me in

well if you got the magic sweets question right your fine :wink:

Reply 2176

Sereni

Original post by tophothari

1 to 1. well at least it is for me as i used NaOH.

Using lactic acid and its salt my ratio was 2.04:1

Reply 2177

InsaneFandom

SO pissed.
I needed an A in that

Reply 2178

VetApplicant2011

Original post by Acta Non Verba

I thought the same. I figured if you're breaking bonds the enthalpy must increase and as the system is becoming more disordered the entropy must also increase.

Annoyingly I think I put negative for the enthalpy accidentally. =[.

Can anyone tell me what they wrote on the lines for the born haber cycle?

Half way down I put one of the molecules as still gaseous and one of them as aqueous, then the bottom one I put both molecules aqueous..

Anyone else always just write it as one line with no little shelfy thing half way down? It threw me ridulous amounts, just sitting staring at the first page going.. WUT? O_o

Reply 2179

blush.ox

Original post by Heatheroink123

For the weakest acid to strongest acid thing, I got ethanoic as the weakest and pyruvic as the strongest. My method being the higher the pKa, the lower the Ka and the lower the Ka, the weaker the acid. Can anyone confirm this?