Year 12s: what will be the first way you research your future options? >>

AQA CHEM5 A2 Chemistry - 19th June 2013

Scroll to see replies

Reply 280

Nstar184

Thank you so much!! :smile:

Reply 281

evan almighty

Original post by Nstar184

Thank you so much! :smile:

No worries! I'm just curious...are you resitting CHEM4 or is it revision for the EMPA/ISA?

Reply 282

Nstar184

Original post by evan almighty

No worries! I'm just curious...are you resitting CHEM4 or is it revision for the EMPA/ISA?

ISA revision..I couldn't find the mark scheme for the paper I did

Reply 283

Hart1995

Does anyone have a document they could attach of the colours of transition metal ion/complexes please?

I find learning them so hard!!

Posted from TSR Mobile

Reply 284

Jessica-F

Original post by Tullia

Attached.

Credit to LogicGoat, as that is who posted them originally.

Thank you both. :biggrin:

Reply 285

laurawoods

Original post by Tullia

Attached.

Credit to LogicGoat, as that is who posted them originally.

Hello, pls can you help me with this question , I am a bit desperate!

Please can you have a look at question 2c )
http://papers.xtremepapers.com/AQA/Chemistry/2002%20Jun/AQA-CHM5-W-MS-Jun02.pdf

I don't really understand why it is -0.84 and not the positive value because I thought that the iron is oxidised. So 0.40+0.44 ---> 0.84 V
How come it is positive value?

Reply 286

username890104

Original post by Hart1995

Does anyone have a document they could attach of the colours of transition metal ion/complexes please?

I find learning them so hard!!

I've attached a couple of links that might help you out.

Original post by Tullia

I've attached a couple of links that might help you out.

Hello pls can you help me with the question that I have asked too? Also, do we have to know about silicon tetrachloride for our spec? It appears often in the legacy papers!

Reply 288

Hart1995

Original post by Tullia

I've attached a couple of links that might help you out.

Thats great! Thanks a million!

Posted from TSR Mobile

Reply 289

laurawoods

Original post by Tullia

I've attached a couple of links that might help you out.

Hello ,pls can you answer some of the questions that I have asked u? :smile:

Reply 290

Hdizzle

Original post by Hart1995

Does anyone have a document they could attach of the colours of transition metal ion/complexes please?

I find learning them so hard!!

Posted from TSR Mobile

Here is another one

SCAN0000.jpg519.9KB

Reply 291

AmyLH

Transition metal test tomorrow :eek3:

I seem to be alright with the colours except for Cu which I just keep messing up :rolleyes:

Hopefully I wont do too badly!

Reply 292

Sherlockedd

Original post by AmyLH

Transition metal test tomorrow :eek3:

I seem to be alright with the colours except for Cu which I just keep messing up :rolleyes:

Hopefully I wont do too badly!

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

Reply 293

Chris-69

Is it always the less positive electrode which has a greater tendency to oxidise?

Reply 294

Sherlockedd

Original post by Chris-69

Is it always the less positive electrode which has a greater tendency to oxidise?

I thought the more negative electrode is always oxidised? I.e. Its an reducing agent so if thats what you mean by 'tendency to oxidise' then yes. Idk I might be wrong :L

Reply 295

Chris-69

Original post by Sherlockedd

I thought the more negative electrode is always oxidised? I.e. Its an reducing agent so if thats what you mean by 'tendency to oxidise' then yes. Idk I might be wrong :L

Yes, I said less positive which is essentially more negative :P . I say less positive as you could have one electrode with +0.14V and another as +0.9V etc. where by neither are negative.

Reply 296

laurawoods

Original post by Chris-69

Yes, I said less positive which is essentially more negative :P . I say less positive as you could have one electrode with +0.14V and another as +0.9V etc. where by neither are negative.

The lower electrode potential value (when compared to the standard hydrogen electrode) is oxidised and the one with the higher electrode potential value (again compared to the standard hydrogen electrode) would be reduced. Remember reduction always occurs at the cathode and you should be fine. The more reactive a metal is , the more it wants to be oxidised. Reaction going backwards, right? Makes sense now? :smile:

Reply 297

JenniS

'oxidation of Cobalt 2+ by air in ammoniacal solution' can someone explain what this is please???? :smile:

Reply 298

username890104

Original post by JenniS

'oxidation of Cobalt 2+ by air in ammoniacal solution' can someone explain what this is please???? :smile:

[Co(H₂O)₆]²⁺ (aq) + 6 NH₃ (aq) --> [Co(NH₃)₆]²⁺ (aq) + 6 H₂O (l)

4 [Co(NH₃)₆]²⁺ (aq) is unstable in the presence of oxygen, so Co²⁺ is oxidised to Co³⁺

4 [Co(NH₃)₆]²⁺ (aq) + O₂ (aq) + 4 H⁺ (aq) --> 4 [Co(NH₃)₆]³⁺ (aq) + 2 H₂O (l)

Does that help?

(edited 11 years ago)

Reply 299

JenniS

Original post by Tullia

[Co(H₂O)₆]²⁺ (aq) + 6 NH₃ (aq) --> [Co(NH₃)₆]²⁺ (aq) + 6 H₂O (l)

[Co(H₂O)₆]²⁺ (aq) is unstable in the presence of oxygen, so Co²⁺ is oxidised to Co³⁺

4 [Co(NH₃)₆]²⁺ (aq) + O₂ (aq) + 4 H⁺ (aq) --> 4 [Co(NH₃)₆]³⁺ (aq) + 2 H₂O (l)

Does that help?

It does thanks! I knew those equations I just wasn't sure if they were the right ones for the questions, thank you!