OCR A2 Chemistry Unit 5, F325 15th June 2015

Just some tips for Monday-

-Know your equations for calculations e.g. Kw, buffers, free energy. Even if you are struggling to work out an answer, you can still get marks for your equations.
-Lattice enthalpy- don't forget to times your value by 2 if you have a 2 in front of your element! Practice over and over again how to draw these diagrams.
-Kstab- don't forget the big square brackets outside! Remember not to put water in your expression because it's in excess.
-Learn how to write the perfect answer for a buffer question, because these hold a lot of marks. Check the mark scheme on how it should be worded.
-Kw- if they ask to find the pH of PURE water, write your equation Kw= [H+][OH-] and then you write Kw= [H+]2 You square it because pure water means the concentration of your H+ ions is equal to the conc of your OH- ions.
-Kc only changes with TEMPERATURE- know which way Kc will shift if you increase/decrease temperature.
-When calculating Kc, draw out your table for moles (initial amount, equilibrium amount etc.)
-Learn how to draw concentration-time graphs and rate-concentration graphs, and explain why the graph is zero, first and second order.
-Sc and Zn are not transition metals as they don't have a partially filled d orbital.
-Cr and Cu are the only ones that have 4s1 instead of following the normal pattern of 4s2 in their electronic configuration.
-Remember to draw complex ions with dashed and wedged lines, and brackets with the charge outside. Sometimes they ask for the bond angle too.
-Ligand substitution- know all colours and equations.
-Redox systems- learn to draw the diagram for electrochemical cells, with a voltmeter, aqueous solutions labelled 1 moldm-3, salt bridge and your correct eletrodes.
-And all definitions of course!



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Can anyone help me understand why the answer to b(ii) is this, how do I work that out ?

do you have an image/list of all the colours of transition metals we need to know??

Yeah gonna need to remember those before the exam

Yes


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Can anyone help me understand why the answer to b(ii) is this, how do I work that out ?

Is anyone going to look through the specification for F325 to see where they could ask some tough, and/or unexpected questions like the entirety of our f324 paper?

Your first equation is for the oxygen at the negative electrode.
Your second equation is your overall equation.
Now to work out the equation for the positive electrode, compare your two equations.
Oxygen is making water.
So cross oxygen and water from your overall equation.
You have CH3OH-> CO2 left.
You need to balance your oxygens first as you have two on the right, and only one on the left.
So you put H20 on the left.
Now you have more hydrogens on the left (6), so balance your hydrogens with 6 on the right.
And lastly you balance your no of electrons, and because it's oxidation they go on the right side.

Hope this made sense.


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F321 harder than usual this year
F322 much harder than usual
F324 on another planet to usual
F325...

Its an inevitable truth, that F325 will be killer
+ve = low grade boundaries
-ve = if a hard Q gets you down, your done for

So just keep going for it till the end write everything you know

F325: RIP

~Go Hard Or Go Home

F325: RIP

~Go Hard Or Go Home

Im dreading the redox titration , this year it will be murder

You've got the best profile pic thing - I've been staring at it for 5 minutes straight!

Anyway should be getting on with chemistry revision but the papers are impossible this year!!!

I tried uploading a tesseract but it wouldn't let me :9
Haha yeah i only experienced unit 4. I did hear about AS being quite harder than usual.

Mee too i'm on a little break atm.

How are you prepping for that? Maybe it's a simple percentage purity like some of the other years who knows