Edexcel Chemistry A2 Unit 5 ~ Wednesday 19th June 2013 (Now Closed)

I didn't do unit 4 already did it before and got an A for it!

Nice one, to get in the 100's is respectable in chemistry, you must be happy with that though still?

I find out my unit 5 chem result tomoz, I'm an external candidate so my results get posted home.

Hey there,
I2 + 2S2O3^2- --------> S4O6^2- + 2I-
2Cu2+ + 4I- ---------> 2CuI + I2
it's true that 2 moles of S2O3 give 1 mole of I2. However, remember that according to the second equation, 1 mole of I2 is produced from 2 moles of Cu2+. In other words:
2 S2O3 --------------> 1 I2
and 2 Cu2+ -------------> 1 I2
we are not really concerned with the I- ions as it is the I2 that links the two equations together not the I-.
Hence, you can find the numbers of I2 by dividing 0.00331 mol by 2 to get 0.00155 mol. You would then have to multiply this by 2 to get the number of moles of Cu2+ ions in the 25cm^3 . So 0.00155 * 2 = 0.00331. this means the number of moles of S2O3 is the same as the number of moles Cu2+. In the mark scheme, this step isn't mentioned which is why the answer might seem to be confusing at first. Hope this helped.

Thanks James, I'm sorry to hear about your unit 5 result...You should definitely get a remark/recall! How have you done in other subjects?

I'm only getting better really, through practice and practice, more practice and not being too scared to ask more questions. You're far from pathetic. I really admire anyone trudging through A2 Chemistry, because it is a hard subject. A B is very commendable and it's entirely understandable to get a D and U. Whatever you get, someone has always gotten worse. It sounds like a horrible and silly thing to think, especially as you want to do better for yourself and ultimately nobody else matters in terms of your exams, but the truth is, they do. Boundaries are set on how well everyone else does, and what you're struggling with; chances are, someone else in the country struggles with the same thing too. Difference is, you aren't giving up even though it's easy to, and that's what counts. Unit 1's the foundation, so it's good you've got that solid. Taking units 2 and 4 together will be good for you, and you have a few months yet to get them up It's hard, so don't feel discouraged. I'm basically the same as you but switched over. Got a D in Unit 1 and now a B in unit 2 so you can do it if you made it to A2 So what are you on now in total, a D?

It's all a balancing act George Facer's book is very unnecessary, but the things it does explain, it explains very well, as well as the examiner tips and hints. Try not to read the introductory pages especially in the AS book as it's irrelevant. Look at the practical tips and try to skim over the things you do know, as to have enough time to browse properly over the things you don't know. I didn't spend too much time on Unit 2 organic because organic is my strength. My weakness is inorganic, so I spent a bit of extra time looking at Redox, Titrations, Decomposition of Nitrates and Carbonates and Green Chemistry. Only work when you have enough time, and energy to. Otherwise it'll just go in one ear, out the other. Try a range of things as well. I made Powerpoint slides and put everything about each topic on each slide. It's a bit congested for some, but for me, it worked a treat because I like to see everything at once and condensed.

Yeah, and that can drop you down a hell of a lot because it will always come up. It's just stuff you've got to learn unfortunately. Really dull, and I had a bad teacher for that initially, hence my weakness in inorganic. We were never told what to actually learn in terms of trends, so that really tripped me up the first sitting. I wouldn't have done much better had I known all of that anyway. Yeah, with Unit 5, you should be a lot more confident on Redox eventually Are you alright on Bond Angles?

Ooh nice about your Unit 6. I got 41/60 at AS which is a high C I think. School doesn't let me retake AS practicals either which is a bit of a bummer, because I could do a bit better this time round. I'd have to do a hell of a lot of practicals though if I retook, as you need all B, C and D skills from AS to submit together apparently. At the moment, I've got 13/14, 11/14 and 10/12 which totals to 34/40 which would be converted to 43/60 so it's a low B. Seeing if I can improve that next week, as a B would be great overall.

Hey guys. Sat the nightmare jan paper alongisde unit 4, got 92/120, but Im contemplating doing it again with you guys to try and get the A*, so this should be fun If any of you need help, do ask. Im expecting a lot of organic chem judging from what was on the jan paper.

Hey thanks for the response ! your really reassuring me at the moment I've been taking it a bit easy because I feel for unit 4 I wasted too much time. I'll be doing unit 2 & 4 questions and past papers - and learning unit 4 And well nope funny enough I added up all the UMS I've gained so far and divided by the maximum UMS possible (420) and ended up with 0.6 (60%) so I'm right on a C

I'm fine with bond angles The thing I hate about chemistry the most... equations ! especially ionic equations. Oh god no & redox numbers and (IIIIII) stuck in compound names

Which practicals have you got left to do ? If you need help you can inbox me... I hope they go well !

No problem Oh right, I've done that now, out of interest. The maximum UMS should be 480 at this point without unit 5 :P I'm at 68.75% doing 330/480 x 100 gives me a high C I'm iffy on Ionic Equations too and Redox isn't too bad. I've got Activation Energy, Observation of Complexes and Preparation of Aspirin left.

Thanks

Nope 420 ? Unless you've included your unit 6 lol

And damn ! are they both observation ?

Observation practicals are the only ones we have left to do also... this could explain why we have a practise practical tomorrow - on how to prepare aspirin

I included Unit 6, yes.
Without it, it's 78%, I have 2 more observations, although I don't have to do all of them if I score high in the one tomorrow. So many complex colours to learn!

and the comical expressions on everyone's faces when you have to copy what the teacher's saying, and you can't differentiate between the way they're saying VO₂⁺ and VO..²⁺

What colours ?
Is it like preparation and observation right ? I guess it was silly of me to think you just prepare it since there is a test paper...

& VO2 ? what is that ??? I haven't got a clue how aspirin is prepared

Let me know how it goes ! & best of luck... hopefully your last practical assessment

What colours ?
Is it like preparation and observation right ? I guess it was silly of me to think you just prepare it since there is a test paper...

& VO2 ? what is that ??? I haven't got a clue how aspirin is prepared

Let me know how it goes ! & best of luck... hopefully your last practical assessment

Hello I'm finally home and can ask my question
It says:

"1.49g of ethanedioic acid dihydrate, H2C2O4.2H2O, were dissolved in distilled water and made up to 250 cm3 in a graduated flask. 25.0 cm3 of this solution were acidified with dilute sulfuric acid and then titrated at 70 degrees C by 24.75 cm3 of a solution of KMnO4. Calculate the molarity of the KMnO4 (aq)."

I have the answer in front of me and it says the answer is 0.0191 M but I do not understand the working out at all, it's so confusing if someone could please explain it all to me I would be so grateful

Got 98/120 in unit 1
100/120 in unit 2
60/60 in unit 3
And 90/120 in unit 4

I need to get an A overall so was wondering if anyone knows what I need to get in unit 5 to make the A possible?
I'm really hoping I don't need to retake unit 4 as I think it'll be too many exams to handle in the summer

Many thanks in advance


Posted from TSR Mobile

Hi You need 480 UMS in total to get an A, and you currently have 348, or 132 to go with units 5 and 6 to take. If you got 60/60 for U6, you'd only need 72 in U5 to get an A

Thanks so much

I take it you don't think I'd need o retake unit 4 then?


Posted from TSR Mobile

Not at all- 72UMS is a C or a D I think? You'd have to do significantly worse in your U5 to get worse than that. Just make sure you work hard at getting your U6 as high as possible

Learn the ions responsible for the changes in colour

VO2 is a vanadium compound. You see, the spec wants you to realise that vanadium has variable oxidation states. you might be asked some questions which involve redox potentials and how you can go from one vanadium state to another by mixing with another solution.

Asprin, well the exam paper will tell you how to prepare it, your not supposed to know how to start off, unless of course, your dealing with an organic synthesis question, in which case you will be told what chemical you are starting off with!

Hope this helps!

Also, ask more questions if possible.

Warlord and I will be around as well because we are retaking this again

The colours of transition metal ions in aqueous solution and what happens when more OH- is added, and NH3 is added, and the complexes formed etc. It's an observation.

The assessed practical tells you how it's prepared