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# OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD watch

1. Could anyone please help me on the Buffer Mg question on june 15, I dont understand why the moles of the acid and salt start at one each-.-

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2. (Original post by Dinasaurus)
I think only Ni and Pt can make square planar.
awesome thank you
3. Forsen Boys. This exam is gonna be so easy Kappa. I'm ****ed boys!
4. (Original post by Dinasaurus)
Adding a base to a buffer solution favours the side with the salt. Adding an acid favours the side with the acid correct?
Adding a base will cause an acid-base reaction to occur
So for a buffer to remain the acid must be in excess.
If you mean adding OH- to the HA<=> H+ A- the OH- is "mopped up" by the H+ ions forming water. So the buffer equilibrium shifts right.

Anyway I need sleep if I even want a chance at the OCR hunger games
Good luck everyone!
5. (Original post by Dinasaurus)
I think only Ni and Pt can make square planar.
things like cucl4 are also square planar

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6. (Original post by ranz)
things like cucl4 are also square planar

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CuCl4 is tetrahedral.
7. (Original post by HFancy1997)
Could anyone please help me on the Buffer Mg question on june 15, I dont understand why the moles of the acid and salt start at one each-.-

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previous page shows that acid and conjucatd base are 1moldm3 and next page the q is on mentions how its 1dm3 so 1x1 =1 mole

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8. Guys if you add Magnesium to a buffer solution, which way does the equation shift?

C2h5COOH = H+ + C2H5COO-

I'm guessing Mg2+ reduces the amount of salt and makes more acid?

Wait no, Mg2+ makes acid dissaciate so makes more salt?
9. Could someone quickly explain how ionic size and charge effects lattice enthalpy?
10. (Original post by ReTakingF324/5)
Forsen Boys. This exam is gonna be so easy Kappa. I'm ****ed boys!
Less twitch and more revision could have fixed that

(Original post by Dinasaurus)
Guys if you add Magnesium to a buffer solution, which way does the equation shift?

C2h5COOH = H+ + C2H5COO-

I'm guessing Mg2+ reduces the amount of salt and makes more acid?

Wait no, Mg2+ makes acid dissaciate so makes more salt?
Firstly equilibrium not equation (I'm just being picky as an examiner would - it's nice to get in a good habit). The Mg2+ would react with the acid, so position of Eqbm would shift to the right to restore lost H+ ions. Remember, Mg2+ is a base!
11. (Original post by BioStudentx)
Less twitch and more revision could have fixed that

Firstly equilibrium not equation (I'm just being picky as an examiner would - it's nice to get in a good habit). The Mg2+ would react with the acid, so position of Eqbm would shift to the right to restore lost H+ ions. Remember, Mg2+ is a base!
Oh so that is one of those insoluble bases, is any Metal ion a base?
12. (Original post by Dinasaurus)
Guys if you add Magnesium to a buffer solution, which way does the equation shift?

C2h5COOH = H+ + C2H5COO-

I'm guessing Mg2+ reduces the amount of salt and makes more acid?

Wait no, Mg2+ makes acid dissaciate so makes more salt?
i thought that metal reacts with an acid to form hydrogen given off as a gas and a salt

so it'd be (c2h5coo)2mg
13. (Original post by Dinasaurus)
Guys if you add Magnesium to a buffer solution, which way does the equation shift?

C2h5COOH = H+ + C2H5COO-

I'm guessing Mg2+ reduces the amount of salt and makes more acid?

Wait no, Mg2+ makes acid dissaciate so makes more salt?
Basically, the Mg (and any strong alkali) reacts with the HA to produce the salt. This means that you're effectively taking away the mol of Mg from the mol of HA and adding it to the mol of A-.
The position of the equilibrium shifts to counter the deficit in HA, therefore, reducing the change in pH.
14. (Original post by Dinasaurus)
Oh so that is one of those insoluble bases, is any Metal ion a base?
All metal ions are bases. Saying Mg2+ is basically the same thing as saying Mg(OH)2
15. (Original post by ReTakingF324/5)
Forsen Boys. This exam is gonna be so easy Kappa. I'm ****ed boys!
Can I get some PogChamps in the tsr chat for another U grade student 4Head.
16. (Original post by ShannonD_1697)
Could someone quickly explain how ionic size and charge effects lattice enthalpy?
Erm strong charge means more attractive force, means stronger ionic bond means more exothermic.
If two ions have the same charge then latice enthalpy is more exothermic as radius decreases because it means charge density is higher, as the forces of attraction has to travel less far so it is stronger.
17. (Original post by BioStudentx)
All metal ions are bases. Saying Mg2+ is basically the same thing as saying Mg(OH)2
Keep it coming i'm learning from this
18. (Original post by ReTakingF324/5)
Forsen Boys. This exam is gonna be so easy Kappa. I'm ****ed boys!
What is a forsen?
19. (Original post by BioStudentx)
All metal ions are bases. Saying Mg2+ is basically the same thing as saying Mg(OH)2
20. (Original post by BanterBus)
Can I get some PogChamps in the tsr chat for another U grade student 4Head.
-( ͡° ͜ʖ ͡°)╯╲___U

Don't mind me just taking my U for a walk

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