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AQA CHEM5 A2 Chemistry - 19th June 2013

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Can anyone explain how you calculate the temperature at which the reaction is NOT feasible?

It's the same as the temperature at which the reaction IS feasible, because going above/ below this temperature will make the reaction feasible/ not feasible :smile:

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(edited 10 years ago)

Reply 1861

nathaan5

Original post by PeanutButter2000

I know it's been posted before but i can't find the link to the January paper, could someone put up the link or quote the post it was in please! thanks :smile:

edit: found it!

any chance you could post it :smile:

Reply 1862

lewiszorz

Original post by marleyxd

If the emf of Zn is more negative than Cu it will be oxidised

Will it tell you their emfs?
If not how do you work them out?

Reply 1863

hawraaj313

do we need to know the colours of vandium ions?

Reply 1864

16dan2life

Original post by Puffy14

Also 1/2 bond enthalpy is atomisation?

yes

Reply 1865

Tasha_11

Original post by hawraaj313

do we need to know the colours of vandium ions?

I don't think so

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Reply 1866

16dan2life

Original post by Chris-69

Yeah, that's the question I was talking about! That's what confused me.

hope they don't ask this :frown:

So, ionic bonding with additional covalent character = higher Lattice dissociation but lower mpt?

Reply 1867

Chris-69

Original post by 16dan2life

hope they don't ask this :frown:

So, ionic bonding with additional covalent character = higher Lattice dissociation but lower mpt?

How would that work? Surely if the lattice enthalpy is strong then the melting point would be greater :s-smilie:

Reply 1868

hawraaj313

Spectrophotometry method:
1) Add appropriate ligand to intensify colour
2) Make up solutions of known concentration
3)Measure absorption or transmission
4) plot graph of results or calibration curve
5) measure absorption of unknown and compare.

It might come up :s-smilie:

Reply 1869

Kaii_Smith

Original post by hawraaj313

do we need to know the colours of vandium ions?

No in the text book it say we don't :smile:

Reply 1870

nathaan5

someone must have the jan13 paper :'(?

Reply 1871

strawberyy

Can some please explain 7b(ii) on jan 11.
I don't understand how they get that equation :/

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Reply 1872

Kaii_Smith

Original post by lewiszorz

Will it tell you their emfs?
If not how do you work them out?

It will tell you atleast two so you can work out the third one
For example it might tell you the emf of one cell and then the cells overall emf so you can work out the other one :smile:

Reply 1873

16dan2life

Original post by Chris-69

How would that work? Surely if the lattice enthalpy is strong then the melting point would be greater :s-smilie:

Jan 10
Q 4e

Lattice of AgCl compared with AgBr

AgCl has greater l-diss because chloride ions are smaller than bromide ions, so stronger forces of attraction between Ag+ and Cl- ions. Simple enough

second part, asks why. Answer is, AgCl has ionic bonding with additional covalent character, so forces in the lattice are stronger than pure ionic attractions.