AQA CHEM5 A2 Chemistry - 19th June 2013

Guys for the transition metal equations, if i initally wrote the wrong equation, but then wrote the right one under it would i still get the marks?

Reply 2621

toddyvedda

Can anyone explain why the current was flowing from right to left in that cell? Fairly sure that whatever **** I wrote in the exam was wrong lol

Reply 2622

Anshul91

Original post by Dirtybit

Yes plus or minus like 4. Same as last yr I think though

yeah thats why I asked..

Reply 2623

Padouken

7

Original post by theslav

I wrote down the reaction with water, and said that it will react very slowly due to the ionic bonding; not sure about reacting it with a base though

Wait what question was this lol?

Reply 2624

Hippokrates

20

Original post by erniiee

Yea I got

2Co³⁺ + CH₃CHO + H₂O -> 2Co²⁺ + CH₃COOH + 2H⁺
4Co²⁺ + O₂ + 4H⁺ -> 4Co³⁺ + 2H₂O

OMG that's what I got! If it's right I'll kiss everybody I see today :P I really thought it was completely wrong.

Reply 2625

bananarama2

Original post by marleyxd

So am i but i put the ionic version underneath each one aswell so hopefully it shouldn't matter.
The list principle isn't applied on these questions is it?...

Hopefully they'll accept both. I think what they were trying to avoid is people doing this:

[Al(H2O)6]3+ +3OH- ---> Al(H2O)3(OH)3 +3H2O

Al(H2O)3(OH)3 +3OH- ---> [Al(OH)6]2-

For example.

Reply 2626

blitzle

1

Any thoughts on grade boundaries? I think about 72 for an A maybe! Definitely a harder paper than usual!

Reply 2627

Anshul91

Original post by toddyvedda

Can anyone explain why the current was flowing from right to left in that cell? Fairly sure that whatever **** I wrote in the exam was wrong lol

was it something to do with the concentration the conc in the right compartment was 2 mol and left was 1 mol so equilbrium shifts to the left?

Reply 2628

erniiee

13

Original post by bananarama2

I think it is 1:3

yea okay - I got some strange value like 2.899.. so just rounded to 3.

I also guessed the formula of the ion as [Co(NH₃)₄Cl₂]⁺ paha

Also I swear we don't need to know the colours of silver complexes..and yet they came up! Please tell me that the initial AND final colour was colourless!

Reply 2629

Padouken

7

Original post by toddyvedda

Can anyone explain why the current was flowing from right to left in that cell? Fairly sure that whatever **** I wrote in the exam was wrong lol

Right had less conc so equilibrium displaced to side to produce more cu²+ ions and electrons so electrons will travel right to left. I think!

Reply 2630

jayM

Original post by wrnicholls

Oh my god I did all the overall equations as ionic equations. Is that not right?

So did i!!!!

Reply 2631

bananarama2

Original post by toddyvedda

Can anyone explain why the current was flowing from right to left in that cell? Fairly sure that whatever **** I wrote in the exam was wrong lol

I said because the reaction aims to increase the concentration of Cu2+ ions on the right, so the Copper (on the right) is oxidised to Cu2+ ions releasing electrons. Therefore the RH electrode forms the negative electrode.

Reply 2632

cat-lover

15

Original post by Jessica-F

Yea i have a conditional offer. I think I'll get my other 2 A's but not sure I'll get it in Chem now. Need 80 UMS for overall A, then again it depends on my ISA aswel. I just hope I havent messed it up too much. Would love an unoffical MS to calm me down.

I'm sure you'll do fine! :smile:

By the looks of it, the grade boundaries could be lower this year. For Jan 2013, you needed 62 raw marks to get 80 ums so going by that you can drop 38 marks and still be alright. Hopefully you'll get an A* in one of your other subjects so that if in the worst case scenario you don't get an A, they offer you the place anyway (I know that has happened to a few people). And I know right, someone really needs to make one. I have physics to study for and I got too many things wrong to make one myself. :tongue:

Reply 2633

HELPIMSTUCK

Original post by erniiee

Also I swear we don't need to know the colours of silver complexes..and yet they came up! Please tell me that the initial AND final colour was colourless!

I thought so - I put no visible change aswell

Reply 2634

bananarama2

Original post by erniiee

yea okay - I got some strange value like 2.899.. so just rounded to 3.

I also guessed the formula of the ion as [Co(NH₃)₄Cl₂]⁺ paha

Also I swear we don't need to know the colours of silver complexes..and yet they came up! Please tell me that the initial AND final colour was colourless!

I got that ratio too.

I'm unsure about the complex.

I think so.

Reply 2635

itssochaotic

omg you are kidding me, for the overall equations we had to write NaCo3???? and HCL??? SHOOOT.

Reply 2636

Milkandcookies5

Original post by Anshul91

was it something to do with the concentration the conc in the right compartment was 2 mol and left was 1 mol so equilbrium shifts to the left?

I think it was as follows:

[Cu2+] on LHS is less than on RHS. Therefore, the equilibrium:

Cu2+ + 2e- <---> Cu shifts LEFT to oppose the reduction in Cu2+ conc.

This releases more electrons, so LHS is relatively negative to RHS

Therefore current flows right to left. Did anyone else get 1:3 for the last question?

Reply 2637

cat-lover

15

Original post by erniiee

yea okay - I got some strange value like 2.899.. so just rounded to 3.

I also guessed the formula of the ion as [Co(NH₃)₄Cl₂]⁺ paha

Also I swear we don't need to know the colours of silver complexes..and yet they came up! Please tell me that the initial AND final colour was colourless!

I wrote down both as colourless so I'm hoping that's right. :tongue:

Reply 2638

temi1234

10

Original post by HEH95

I don't remember all the questions by any means, but here's the numerical answers I got..sound familiar to anyone?

+1026 kJmol-1 (everyone got about +9hundred and something)
+13 kJmol-1

284.2 K (I got less than that)

+44.5 JK-1mol-1

+242.08 kJmol-1

-3.05 V

4.28x10^14 s^-1

ratio of 3:1

thoughts...?

I got the same for those in bold, those not in bold either i don't remember or got a different answer