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

1. 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.
2. Is there any chance anyone has a link to the specimen paper and Jan 2012 paper and markschemes? I think I saw it posted itt before but cant find it now.
3. (Original post by niaghez)
i found jan 2012 waaay harder than jan 2011, jan 2011 was much easier in my opinion lol
I agree! I did jan2012 paper and found it bloody hard.. :/ but most other people found it relatively easy
4. (Original post by arvin_infinity)
Anyone knows where I can get hold of a MS to the specimen paper
scroll down right to the bottom
5. (Original post by Robpattinsonxxx)
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!
Ok here are the rest of my answers
9. An endothermic reaction can take place spontaneously if delta S (entropy change) is positive and the temperature is high because if temp is high and delta s is positive then TdeltaS will be large and therefore delta h will be smaller than Tdelta S therefore delta G will be less than 0 so the reaction is feasible.
10. A reaction that isn't feasible at high temperatures is an exothermic reaction in which entropy decreases because at high temperatures the value of Tdelta S is a large negative value and then delta h minus the large negative value is the same as delta H plus the large value, therefore delta G is bigger than 0 so the reaction isn't feasible.
11. The metal ion /metal ion and the non-metal/metal ion. Oh god um...don't know why it's used exactly..maybe because an electrical current needs to flow through the wire so there needs to be some sort of metal electrode?
12. Not sure whether you mean in general ie with gibbs energy thing or in an cell...in a cell a reaction won't be feasible under non-standard conditions because by changing concentrations, for example, the value of E changes, etc (cba to go into detail haha) and also it wont be feasible if the activation energy is too high. For normal gibbs energy it wont be feasible if, for example the reaction is endothermic and delta S is negative.
13. This is the same as the alkaline fuel cell, right? Equations are:
anode: h2 +2oh- ---> 2h2o +2e
cathode: 0.5 O2 + h2o +2e ---> 2OH-
Overall: 0.5 O2 + h2 ---> h20

14. Hydrogen rich fuels, eg methanol are hydrocarbons that are used as fuels and contain a lot of hydrogen and can be converted into hydrogen using a reformer? (Not sure about this one!)
6. (Original post by niaghez)
scroll down right to the bottom
Never bothered to scroll down ..was using the same file.. never realised what's at the bottom
7. (Original post by arvin_infinity)
Never bothered to scroll down ..was using the same file.. never realised what's at the bottom
lol khar
8. Does anyone know/have the list fo F325 definitions we need to learn overall?
9. Good luck guys! I'll be doing this next year so will be able to feel your pain then...
10. (Original post by Alexandra's Box)
Good luck guys! I'll be doing this next year so will be able to feel your pain then...
It's actually a pretty decent module. No annoying stuff like green chemistry and there is loads of maths
Does anyone know/have the list fo F325 definitions we need to learn overall?
These are all the ones on the spec:

http://flashcarddb.com/cardset/13611...ons-flashcards
12. (Original post by Robpattinsonxxx)
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

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!
13. Love you boss
14. (Original post by niaghez)
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
Some of the enthanoic acid neutralises all of the alkali.
Find the amount of ethanoic acid remaining and then just use the acid dissociation equation to find [H+] and then the pH. (Remember that the volume of the solution is 10 + 20cm3. )

(Original post by niaghez)
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.
Similar to the one above except this time the alkali is in excess.
Firstly find how much alkali remains after the reaction takes place.
Now remember KOH dissociates almost completely so use this to find [OH-] and then [H+] (Or pOH and then directly pH, whichever method you prefer.)

1.Definition of a d block element [1]

An element where d is the highest energy subshell.

2. Configurations of copper and chromium [2]

Copper (29) 1s2 2s2 2p6 3s2 3p6 4s1 3d10
Chromium (24) 1s2 2s2 2p6 3s2 3p6 4s1 3d5

3. Colour changes in precepitation reactions of Cu2+, Co2+, Fe2+ and Fe3+ with NaOH [4]

Cu2+: pale blue solution to a pale blue precipitate.
Co2+: pink solution to a blue precipitate turning beige in the presence of air.
Fe2+: pale green solution to a pale green precipitate turning rusty brown on its surface in air.
Fe3+: pale yellow solution to a rusty brown precipitate.

4. How do transition metals act as catalysts? [3]

Transition metals provide a surface on which a reaction can take place. Reactants are adsorbed onto the surface and held in place while the reaction occurs .After the reaction, products are desorbed from the surface and the metal is remained unchanged.

5. When do complexes form square planar? [1].

The complex must contain two different ligands with two of one ligand and two of another.

6. Give an example of a bidentate ligand [1]

Ethane-1,2-diamine. :NH2CH2CH2NH2:

7. Describe the action of cis platin and give its complex formula [4]

Cis platin is a drug against cancer. Its other isomer is trans platin. Cis platin acts by binding to the DNA of fast growing cancer cells, altering the DNA. Cells are prevented from reproducing by changes to the DNA structure. Cells cannot divide and so die. Activation of a cell’s own repair system leads to death of cancer cell. Unfortunately it has some unpleasant side effects.

8. What is a multidentate ligand? [1]

A multidentate ligand has more than one lone pair of electrons and can form more than one coordinate bond to the central metal ion.

9. Colour changes in ligand substitution reactions using [Cu(H2O)6] with ammonia and chloride ions and [Co(H2O)6] with chloride ions [3]

[Cu(H2O)6] and NH3. Pale blue solution to a deep blue solution.
[Cu(H2O)6]and Cl4. Pale blue solution to yellow solution.
[Co(H2O)6] and cl4. Pink solution to deep blue solution.

10. What is ligand substitution? [1]

A reaction in which one ligand in a complex ion is replaced by another ligand

11. What is kstab? [1] What does a larger kstab value tell you? [1]

Kstab is the equilibrium constant for the formation of a complex ion in a solution from its constituent ions. A large kstab value results in the formation of a stable complex ion.

12. Describe colour changes in redox titrations using MnO4- /Fe2+ and I2/S2O32-. Give equations of the titrations [5]

MnO4-+8H++5Fe2+Mn2++5Fe3++4H2O. Purple to pale pink/colourless

2S2O32-+I22I-+S4O62-+2I-
2Cu2++4I-2CuI+I2. Light brown precipitate to blue/black colour (starch) to colourless.
16. (Original post by zozzie94)
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!
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.
17. (Original post by Robpattinsonxxx)
x

I think fuel cells are likely to come up so it's worth going over that section. Always seems to catch people out.
18. (Original post by Robpattinsonxxx)
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.
Haha ok thanks And yeah i literally only just learnt the definition for kstab a few days ago because it was the only one I didn't know so I had a sneaky feeling it might come up just to spite me...so i learnt it...
19. (Original post by Dreamweaver)

I think fuel cells are likely to come up so it's worth going over that section. Always seems to catch people out.
Thankyou
20. Found some useful booklets a while ago.
Attached Files
21. 5.1.1 How fast.doc (477.5 KB, 2173 views)
22. 5.1.1 How fast Answers.doc (508.0 KB, 132 views)
23. 5.1.2 How Far.doc (132.0 KB, 2533 views)
24. 5.1.2 How Far Answers.doc (494.0 KB, 148 views)
25. 5.2.2 Enthalpy and Entropy.doc (148.5 KB, 592 views)
26. 5.2.2 Enthalpy and Entropy Answers.doc (219.0 KB, 139 views)
27. 5.2.3 Electrode Potentials and Fuel Cells.doc (189.5 KB, 3166 views)
28. 5.2.3 Electrode Potentials and Fuel Cells Answers.doc (273.0 KB, 181 views)
29. 5.4.1 Synoptic.doc (304.0 KB, 501 views)
30. 5.4.1 Synoptic Answers.doc (482.0 KB, 198 views)

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