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# AQA - Unit 5 - Energetics, Redox and Inorganic Chemistry watch

1. (Original post by Sparkly-Star)
Cos we're forming AgCl which contains only 1 Cl-
I think I get it now..Thanks Also, for 8c, whats the overall equation? I don't know how to work it out to see the moles of phosphorus oxide. Sorry I'm askingso many qs Thanks
2. (Original post by Sparkly-Star)
I doubt anything from unit 4 will come up maybe bits and bobs from unit 1/2 so things like percentage yield and so on, energetics, extraction of metals maybe.
Extraction of metals?
haha!

I can just about remember electrolysis of Aluminium, and the copper/scrap iron one

But nothing else!
3. Can Anyone help me do this

20.0 cm3 of an acidified solution of H2O2 was found to react with exactly 15.7 cm3 of a 0.0180 mol dm–3 solution of potassium manganate(VII).
Calculate the concentration, in g dm–3, of the solution of hydrogen peroxide.

Eq - 2MnO4– + 5H2O2 + 6H+ = 2Mn2+ + 5O2 + 8H20

I can get the no of moles of H202 but what do i do next?
4. just a reminder of enthalpy change equation (unit2 stuff) q=mc^T
5. This is one of them synoptic things, its from unit
6. hey guys do we need to know any stuff from unit 1 to 4 for the unit 5 exam??? .... ive come across some questions in the textbook at the back which hve some (wot look like) 'synoptic' questions.... if so would we hve 2 remember the reactions from unit 2??? i knw thers stuff the overlap into units 1 n 2 which r in unit 5.. which is fine as we hve 2 learn it for unit 5 but would ther b any reactions from unit 2 n 4?? etc??
7. Shame on me, I re-took unit 2 and I already forgot everything.
8. This is one of the synoptic things, and it was in unit 1, I jus wanna highlight it and ask:

Li has a smaller atomic radius so is more polarising than Na+ hence in combination with Oxygen it would have a higher melting point.

But what about LiCl or LiBr which one would have a higher melting point, and I ask this because Br- has a bigger atomic radius than Cl- so its more easily polarised and rather than having just ionic bonds you would have covalent bonds too....

right?
9. (Original post by Mobs25)
hey guys do we need to know any stuff from unit 1 to 4 for the unit 5 exam??? .... ive come across some questions in the textbook at the back which hve some (wot look like) 'synoptic' questions.... if so would we hve 2 remember the reactions from unit 2??? i knw thers stuff the overlap into units 1 n 2 which r in unit 5.. which is fine as we hve 2 learn it for unit 5 but would ther b any reactions from unit 2 n 4?? etc??
Unit 5 isnt synoptic of unit 4, even check the specfiication,
But they can mention anything they want from unit 2 and unit 1
10. Does anyone else feel a bit ****'ed for this exam? :P
11. (Original post by Sparkly-Star)
From the top of my head, it is less mathematically BUT think of it as fireworks which is exo. If you had fireworks and had one of them sparkly things it might be -998 which is small but if you had one of those big fireworks in the air (whatever they're called ) those are greater -1025 hence it is MORE exo.

Lattice enthalpy increases as the size of the ions decreases this is because the ions are more attracted I think.

Electron affinity, not sure.
Are u using enthalpy of lattice dissociation or enthalpy of lattice formation?

From what I understand, what you said is true with dissociation but I can't explain the trend in terms of formation. Correct me if I'm wrong please: My explanation would be: as ionic size increases,lattice enthalpy of formation becomes less negative because more energy is required to bring larger ions together because larger ions are far apart.
12. (Original post by NRican)
Can Anyone help me do this

20.0 cm3 of an acidified solution of H2O2 was found to react with exactly 15.7 cm3 of a 0.0180 mol dm–3 solution of potassium manganate(VII).
Calculate the concentration, in g dm–3, of the solution of hydrogen peroxide.

Eq - 2MnO4– + 5H2O2 + 6H+ = 2Mn2+ + 5O2 + 8H20

I can get the no of moles of H202 but what do i do next?
First thing I'd do is find the moles of potassium permanganate, you have the volume and the concentration so use the formula

(c*v)/1000 = moles

Seeing as it reacts exactly just divide the answer you get by 2 and times by 5 to get moles of H2O2.

moles = grams/RAM
grams = moles*RAM
then grams/1000 = gdm-3?

I think that's right?
13. Is it just me or was the specimen paper quite different to the 3 actual papers?
also seemed to have a lot more synoptic in than the 3 actual papers..
14. (Original post by mzoorw)
First thing I'd do is find the moles of potassium permanganate, you have the volume and the concentration so use the formula

(c*v)/1000 = moles

Seeing as it reacts exactly just divide the answer you get by 2 and times by 5 to get moles of H2O2.

moles = grams/RAM
grams = moles*RAM
then grams/1000 = gdm-3?

I think that's right?
Here is the mark scheme

[H2O2] = 7.065 × 10^–4 × 1000/20 (1) = (3.53 to 3.54) × 10^–2
Mass = moles × Mr = 3.53 × 10^–2 × 34
= 1.2(0) (1)

Why times by 1000/20

Is it because 20cm3 was used so we need to times by 50 to get dm3
15. Anyone know what the grade boundaries from jan10, june10 and jan11 were??
16. Why are Transition metals good catalysts ? I under stand heterogeneous and homogeneous catalysis but never understand why overall they are good at catalyst ?
17. (Original post by Zabukar)
Why are Transition metals good catalysts ? I under stand heterogeneous and homogeneous catalysis but never understand why overall they are good at catalyst ?
They have variable oxidation states
18. (Original post by strawberry_cake)
Anyone know what the grade boundaries from jan10, june10 and jan11 were??
Jan 11 and June 10 were both 73 for an A, 82 for A*

EDIT: Found Jan 10, 72 for an A
19. (Original post by Arab_Empress)
Unit 5 isnt synoptic of unit 4, even check the specfiication,
But they can mention anything they want from unit 2 and unit 1
I may be wrong but I was under the impression that it is only synoptic for the topics in Unit 5. So they can ask anything we've previously learnt about on Inorganic, Energetics and Redox but not things like Organic as Unit 4 has a synoptic element for that.
Basically, any AS knowledge that was built upon in Unit 5, we can be asked questions on.

On the OLD specification there was an extra synoptic paper across the entire syllabus but now Units 4 and 5 are both "semi-synoptic" so to speak. Unit 5 cannot include Unit 4 knowledge because they can be taken in either order.
20. Can I confirm, that cisplatin has two NH3 ligands right?

The AQA Nelson thornes book says it's NH2.

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