OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012

i found jan 2012 waaay harder than jan 2011, jan 2011 was much easier in my opinion lol

Anyone knows where I can get hold of a MS to the specimen paper

Module 2 then peeps

9. How do endothermic reactions take place spontaneously [3]
10. Why does a reaction not become feasible at high temperatures [2]
11. Out of cells from metal/metal ion half cells, non metal/metal ion half cells and metal ion/metal ion half cells, which two half cells need to be conducted with at least a platinum electrode [2]. Explain why it is used [1]
12. Explain two reasons why a reaction may not be feasible [2]
13. In an hydrogen-oxygen fuel cell give the equations at the anode, cathode and the overal equation [3].
14. What are hydrogen rich fuels [1] Give an example of one [1]


Out of 43 i think. GO GO GO! Then you revised module 2!

http://pdf.ocr.org.uk/download/assess_mat/ocr_7770_sam_gce_unit_f325.pdf?
scroll down right to the bottom

Never bothered to scroll down ..was using the same file.. never realised what's at the bottom

Good luck guys! I'll be doing this next year so will be able to feel your pain then...

Does anyone know/have the list fo F325 definitions we need to learn overall?

1. Definition of a d block element [1]
2. Configurations of copper and chromium [2]
3. Colour changes in precepitation reactions of Cu2+, Co2+, Fe2+ and Fe3+ with NaOH [4]
4. How do transition metals act as catalysts? [3]
5. When do complexes form square planar? [1]
6. Give an example of a bidentate ligand [1]
7. Describe the action of cis platin and give its complex formula [4]
8. What is a multidentate ligand? [1]
9. Colour changes in ligand substitution reactions using [Cu(H2O)6] with ammonia and chloride ions and [Co(H2O)6] with chloride ions [3]
10. What is ligand substitution? [1]
11. What is kstab? [1] What does a larger kstab value tell you? [1]
12. Describe colour changes in redox titrations using MnO4- /Fe2+ and I2/S2O32-. Give equations of the titrations [5]

Out of 28

At 25 °C, the acid dissociation constant Ka for ethanoic acid has the value
1.75 × 10–5 mol dm–3.
2 (c) (i) Calculate the pH of the solution formed when 10.0 cm3 of 0.154 mol dm–3 potassium
hydroxide are added to 20.0 cm3 of 0.154 mol dm–3 ethanoic acid at 25 °C.

HOW DO I DO THIS

oh and this:

Calculate the pH of the solution formed when 40.0 cm3 of 0.154 mol dm–3 potassium
hydroxide are added to 20.0 cm3 of 0.154 mol dm–3 ethanoic acid at 25 °C.
At 25 °C, Kw has the value 1.00 × 10–14 mol2 dm–6.

1. A d block element is an element which has its electrons with the highest energy in its d orbitals (ie outer electrons in the d orbitals).
2. copper: I'm gonna put spaces between them otherwise it looks confusing but obvs in an exam i wouldnt haha: 1s2 2s2 2p6 3s2 2p6 4s1 3d10
chromium: 1s2 2s2 2p6 3s2 3p6 4s1 3d5
3. Colour change with cu2+ is pale blue solution to blue precipitate, with co2+ it's pink solution to blue precipitate which turns beige in the air (cos its oxidised), with fe2+ green solution to green precipitate which turns rusty brown in oxygen because the fe2+ ions are oxidised to fe3+, with fe3+ its pale yellow solution to rusty brown precipitate.
4. There are 2 ways they act as catalysts: 1. they provide a metal surface for the reaction to occur on so the reactants are adsorbed onto the surface and held in place to react there and then the products are desorbed off and the surface is unchanged. 2. They bind to the reactants forming intermediates as part of a chemical pathway with a lower activation energy.
5. Ok I'm not 100% sure about this but I think it's when there's 4 multidentate ligands (ie you would think it would be tetrahedral) but there are cis and trans isomers.
6. h2Nch2ch2nh2 ie ethane-1,2-diamine
7. Cis platin is used as an anti-cancer drug. It works by binding to the cancer cells and preventing them from reproducing, therefore killing them. Not really sure how to show it's structure without drawing it...but it has 2 chlorine ligands and 2 nh3 ligands and a central Pt ion...and its square planar and obviously the cis isomer so the cl ligands are next to each other on the bottom.
8. A ligand that donates more than one lone pair of electrons to the central transition metal ion forming more than one coordinate bond.
9. The colour change with the copper ligand and ammonia is it starts of as a pale blue solution and when you add a bit of ammonia a pale blue precipitate is formedthen when you add excess ammonia this dissolves to form a deep blue solution. With copper ligand and cl- ions, it goes pale blue solution then green solution then yellow solution. With cobalt its pink solution to blue solution.
10. Ligand substitution is a reaction in which one ligand is substituted for another ligand.
11. Kstab is the equilibrium constant existing between a transition metal ion surrounded by water ligands and the complex that forms when ligand substitution takes place. Large kstab means equilibirum shifts to the right ie the products side and therefore that complex ion is more likely to form.
12. Oh god...I swear we don't need to know the exact colours, do we?! I just know that in the mno4 and fe, end point is colourless to pink and in the eequation, the mol ratio of fe to mno4 is 5 to 1...and then in the iodine one i think at first it's dark brown (white precipitate in a brown solution) and then eventually turns straw coloured which is when you add the starch indicator so then it turns blue black because of the iodine present and then at end point its colourless and a white precipitate is formed and the reactions are
2cu2+ + 4 I- ---> 2cuI +I2 and 2S2O3 2- + I2 --> 2I- + s4o6 2-

Thanks for the questions!

x

Well done your answers pretty much match mine. I should learn myself what kstab really means. and i never knew that about the colour changes with co2+ and Fe2+ with them being oxidised.

Nice answers + rep

I think fuel cells are likely to come up so it's worth going over that section. Always seems to catch people out.