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CIE chemistry A level paper 4 variant 2

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Original post by Wallflower73
nah nah the one where you had to write an expression, units and later find the partial pressure for the two compounds


You must have done a different variant bc variant 2 had no Kp
Original post by Demaciaaa
What is the unit of Kp in that question? I wrote atm^2


I don't remember there being a Kp question!! @__@ But there was a Kc question afaik and if I remember correctly I wrote mol^5dm^-15
Original post by Wallflower73
nah nah the one where you had to write an expression, units and later find the partial pressure for the two compounds


You must have done a different variant: variant 2 had no Kp, but a lot of Kstab
Original post by andysalad
One of the three had no chlorine; the other two were 2) CH3CHCl-R-CO2H and 3) CH3-R-CHClCO2H. Exact position of chlorine was probably different to what I said but essentially the smaller distance of the chlorine from the oxygen weakened the strength of the O-H bond making the 3rd one more acidic.


Correct :biggrin:
1. Everyone said hydrogen bonding.. I was like the only one who said ion-dipole interactions.. Crud.. xD
2. Yap.. Same. (water vapour at first, brown gas in the end)
3. Now, this is the thing.. I felt that the enthalpy change would JUST be the same because HCl and HNO3 both dissociate almost fully in water and it would leave almost "no effect." That is if I articulated well. All I wrote in the paper was that with the two acids, the ionic equation would still be about the same so.. Again crud..
4. The only thing I said was that bidentate ligands were more stable (this is the damn conclusion).. I also said the products are energetically more stable than the reactants (also conclusion instead of explanation).. After searching, I found out it was possibly because there are more moles on the products in equilibrium II. That level of analysis is crazy for just a one mark question.. xD
5. My concentration was too big. I think I got 7 mol dm-3 or something. Way too much to dilute a 1 x 10^-4 mol dm-3 to a 1 x 10^-7 mol dm-3. I just used random "initial concentration, reacting concentration, equilibrium concentration" thing and everything just got weird..
6. I said one of them was more acidic because one weakens the -OH bond more because one alkyl group is more electron-donating, so the the electrons are pulled more toward the C=O bond and make a more delocalised strucutre, less H+ blah blah blah
7. I have no clue. I wrote CH3NH2 + H+ -> CH3NH3+
CH3NH3Cl -> CH3NH3+ + Cl-.I'm way off from you guys..

In conclusion, shoot.
Original post by jessedoell
You must have done a different variant bc variant 2 had no Kp


omg I just realised that I did 41 lol
Original post by jboentoro
You must have done a different variant: variant 2 had no Kp, but a lot of Kstab


yep! i did variant 41 i just remembered
What did you guys write for the voltage of Ag+/Ag and Fe2+/Fe3+?
Original post by Demaciaaa
What did you guys write for the voltage of Ag+/Ag and Fe2+/Fe3+?


Didn't it ask for the cell voltage between Ag+/Ag and the standard hydrogen electrode?
Original post by Dohaeris
Didn't it ask for the cell voltage between Ag+/Ag and the standard hydrogen electrode?

I remeber it asked you to write an equation between Ag+/Ag and Fe3+/Fe2+ and calculate the voltage, I wrote 0.03V which seems possible but that's what I read from data booklet
Original post by Demaciaaa
I remeber it asked you to write an equation between Ag+/Ag and Fe3+/Fe2+ and calculate the voltage, I wrote 0.03V which seems possible but that's what I read from data booklet


Variant 42?
Original post by Dohaeris
Variant 42?


I did variant 1:frown:
Original post by Demaciaaa
I did variant 1:frown:


Ah, I guess that's why then.

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