Aqa a2 chem5 19th june 2012

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Ah, CHEM5...

I love the way it lulls you into a false sense of security with the few chapters.

Starting to remember the colours and formula of the TM complex ions though.

We've got Period 3 to go yet but that's our final chapter... everything else is just solid revision until the exam.

Haha I completely agree about the false sense of security :lol:

. First youre going throgh the first two chapters thinking "ah this is too easy, almost AS". Then chapters 4...5..6 hit ya and you're like "The faq is this supposed to be". Then you realise you actually have to memories the colours.

Good times :frown:

How's everyone's revision coming along? :h:

Reply 21

wibletg

Original post by Doctor.

Haha I completely agree about the false sense of security :lol:

How's everyone's revision coming along? :h:

I haven't quite started, but I think I know the colours and the formula of them...

There's sort of a pattern to them if you remember the awkward ones (Copper and excess ammonia, chromium in general, cobalt and excess ammonia, aluminium and excess hydroxide).

Reply 22

izzo

Original post by al_habib

there is chemistry tuition if you need any help or support for only £9 per class.

tuition from whom?

Reply 23

wibletg

Original post by masterhr1

Can anyone help me with this question:

Write an equation to show why aqueous chromium(III) chloride is acidic.

I wrote:

[Cr(H2O)₆]³⁺ + 3OH^- --> [Cr(H₂O)₃ + 3H₂O

The answer though is:

[Cr(H₂O)₆]³⁺ + H₂O → [Cr(H₂O)₅(OH)]²⁺ + H₃O⁺
OR [Cr(H2O)6]3+ → [Cr(H2O)5(OH)]2+ + H+
DO NOT allow reactions with bases other than water
Allow loss of up to 2 H+

Did i do it right or am I making a mistake?

I'd say you did it wrong... sorry.

It states do not allow reactions with bases other than water :smile:

Could be wrong though.

(edited 12 years ago)

Reply 24

thegodofgod

Original post by masterhr1

Can anyone help me with this question:

Write an equation to show why aqueous chromium(III) chloride is acidic.

I wrote:

[Cr(H2O)₆]³⁺ + 3OH^- --> [Cr(H₂O)₃(OH)₃] + 3H₂O

The answer though is:

[Cr(H₂O)₆]³⁺ + H₂O → [Cr(H₂O)₅(OH)]²⁺ + H₃O⁺
OR [Cr(H2O)6]3+ → [Cr(H2O)5(OH)]2+ + H+
DO NOT allow reactions with bases other than water
Allow loss of up to 2 H+

Did i do it right or am I making a mistake?

The OH^- group does show that [Cr(H₂O)₆]³⁺ is acidic, as it donates a proton to the OH^-, to form H₂O.

However, the complex you have being produced is wrong :redface:

Only 1 proton is lost per complex, rather than 3, thus forming [Cr(H₂O)₅(OH)]²⁺_(aq), instead of [Cr(H₂O)₃(OH)₃]_(s).

Ultimately, the mark scheme says not to allow any reactions with bases other than water, and OH^- is hydroxide, not water. :redface:

Reply 25

thegodofgod

Original post by sophianth

Does anyone have jan 2012 aqa paper for unit 5,plz???
I couldn't find it on any website :frown:

(
Thank you very much :h:

Did you find it?

If not, I've attached it.

I seem to have lost AQA-CHEM5-W-MS-JAN12 though :s-smilie:

AQA-CHEM5-W-QP-JAN12.pdf566.6KB

Reply 26

al_habib

Original post by izzo

tuition from whom?

there are couple of my friends including myself, the tuition is in Rusholme,Manchester.if you need more info please feel free to ask.

Reply 27

Sheo

Do we need to know the equations for when the aqua ions react w/ OH-, NH3 and CO3 2-? Thanks :smile:

Reply 28

wibletg

Original post by Sheo

Do we need to know the equations for when the aqua ions react w/ OH-, NH3 and CO3 2-? Thanks :smile:

Yes.

The majority are fairly generic.

Reply 29

Sheo

Original post by wibletg

Yes.

The majority are fairly generic.

Yes went through them yesterday and they're all pretty similar. :smile:

Reply 30

lovemenot

Original post by thegodofgod

Here's CHEM4.

Don't think there is a CHEM5 in January; only in June.

Any chance of having Chem 2 Jan 12 question paper? Please post if you do cause I really want to look up and see why I did so badly and hopefully revise those I had missed out for the retake.

Reply 31

thegodofgod

Original post by lovemenot

Any chance of having Chem 2 Jan 12 question paper? Please post if you do cause I really want to look up and see why I did so badly and hopefully revise those I had missed out for the retake.

Sorry, I've only got the papers for the units I'm sitting this June, CHEM4 and CHEM5 :s-smilie:

Reply 32

wibletg

Going to literally hammer this to get an A* in Chemistry now :frown:

I need 113/120, not looking likely. Especially since I'm fully expecting the examiners to screw us over like they did in January for CHEM4 and June in CHEM2.

Also, does anyone know the reactions of the halides with concentrated sulphuric acid? I don't have an AS textbook anymore, it'd be much appreciated? :tongue:

Reply 33

Alpha5

How do you guys thing Chem 5 compares Chem 4. I think it's better, as it's more precise where as Chem 4 requires you to now alot about alot, organic mechanisms and tests. Crazy stuff.

Reply 34

wibletg

Original post by Alpha5

How do you guys thing Chem 5 compares Chem 4. I think it's better, as it's more precise where as Chem 4 requires you to now alot about alot, organic mechanisms and tests. Crazy stuff.

There's more memory involved but once you've started to remember everything it gets better :tongue:

The only thing that's likely to be a sting in the tail is the synoptic link :frown:

Reply 35

thegodofgod

Original post by wibletg

Going to literally hammer this to get an A* in Chemistry now :frown:

Fluoride and chloride ions won't reduce concentrated sulphuric acid.

Bromide ions reduce the sulphuric acid to sulphur dioxide. In the process, the bromide ions are oxidised to bromine.

Iodide ions reduce the sulphuric acid to a mixture of products including hydrogen sulphide. The iodide ions are oxidised to iodine.

Therefore, reducing ability of the halide ions increases as you go down the Group.

Reply 36

wibletg

Original post by thegodofgod

Thanks

Reply 37

thegodofgod

Original post by wibletg

Thanks

The best thing about those reactions is that you don't have to memorise them - you can work them out yourself using redox half-equations :biggrin:

, e.g.:

Sulfuric acid + Iodide ions.

2 I^- --> I₂
H₂SO₄ --> H₂S.

Just know the reactants and the products, you can then balance the reactions with waters / protons / electrons, and then multiply / cancel electrons and combine the two half-equations to get a full equation for the reaction :cool:

Reply 38

wibletg

Original post by thegodofgod

The best thing about those reactions is that you don't have to memorise them - you can work them out yourself using redox half-equations :biggrin:

Yeah, that's what I was planning on doing :biggrin:

How are you finding CHEM5?

Reply 39

thegodofgod

Original post by wibletg

Yeah, that's what I was planning on doing :biggrin:

How are you finding CHEM5?

Not too bad on the whole, apart from transition metals. All the memorising for the complexes' colours is killing me :frown:

Luckily, though, most of the colours / complexes follow a trend, e.g. Cr (III) complexes are green, Fe (III) complexes are browny, Cu (II) complexes are bluish, etc.

How about you?