OCR Chemistry A F325 Equilibria, Energetics and Elements Wed 13 June 2012
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Original post by The Illuminati
This makes no sense to me. I'd say rate is independent to concentration as no matter how much you change the concentration the rate stays the same.
We are looking at a concentration-time graph. I'd agree with you if we were talking about a rate-concentration graph
Original post by otrivine
what thats a low mark 
but could you like indicate the number of marks for each cause i did not know how much to write
but could you like indicate the number of marks for each cause i did not know how much to writeYou need to be more specific
SHall i create some module 2 questions then?
Original post by Robpattinsonxxx
You need to be more specific
ok
but ionic product of water means same thing? more please cant accpet that low mark after my hard effort
Original post by Robpattinsonxxx
SHall i create some module 2 questions then?
yes
Original post by otrivine
ok but ionic product of water means same thing?
more please cant accpet that low mark after my hard effort
but ionic product of water means same thing? more please cant accpet that low mark after my hard effort
Your definition of kw was fine. I was just asking you to tell me what it actually meant. Maybe i should have been more specific in my questions
Original post by Robpattinsonxxx
Your definition of kw was fine. I was just asking you to tell me what it actually meant. Maybe i should have been more specific in my questions
ok anyways lets do module 2 but please if you can write the number of marks next to each question so i have an idea if you want it in detail or not i would appreciate
Ok ill write up some questions. Answer my question on the communications thread while you wait
Original post by Robpattinsonxxx
Ok ill write up some questions. Answer my question on the communications thread while you wait
wheres the communication thread
Module 2 then peeps 
1. What is the enthalpy change of atomisation. Give equation too [2]
2. WHat is the first electron affinity. Give equation too [2]
3. Wht is the standard enthalpy change of formation. Give equation too [2]
4. What is the enthalpy change of solution? Give an equation. What two processes take place when an ionic solid dissolves? [4]
5. What is the enthalpy change of hydration. Give equation [2]
6. Explain the effect of ionic charge and size on (i) lattice enthalpy [6] and (ii) enthalpy change of hydration [6]
7. Give a definition of entropy [1]
8. Explain the difference in entropy of a solid and a gas [1], the change when a solid lattice dissolves [1] and the change in a reaction where there is a change in the number of gaseous molecules [1]
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!
1. What is the enthalpy change of atomisation. Give equation too [2]
2. WHat is the first electron affinity. Give equation too [2]
3. Wht is the standard enthalpy change of formation. Give equation too [2]
4. What is the enthalpy change of solution? Give an equation. What two processes take place when an ionic solid dissolves? [4]
5. What is the enthalpy change of hydration. Give equation [2]
6. Explain the effect of ionic charge and size on (i) lattice enthalpy [6] and (ii) enthalpy change of hydration [6]
7. Give a definition of entropy [1]
8. Explain the difference in entropy of a solid and a gas [1], the change when a solid lattice dissolves [1] and the change in a reaction where there is a change in the number of gaseous molecules [1]
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!
(edited 11 years ago)
Original post by The Illuminati
Ka is called the acid dissociation constant, so will always be pretty much the same for each time. If H+ increases then so will HA in order to keep Ka the same value...I think
i didn't neg u
I'llPositive rep u too balence it out
cool, that makes sence, but yeh, if peeps disagree, then whats the right answer??
Original post by Smiley Face :)
i didn't neg u
I'llPositive rep u too balence it out
cool, that makes sence, but yeh, if peeps disagree, then whats the right answer??
I'llPositive rep u too balence it out
cool, that makes sence, but yeh, if peeps disagree, then whats the right answer??
lol thanks, i appreciate it
Original post by Robpattinsonxxx
Module 2 then peeps
1. What is the enthalpy change of atomisation. Give equation too [2]
2. WHat is the first electron affinity. Give equation too [2]
3. Wht is the standard enthalpy change of formation. Give equation too [2]
4. What is the enthalpy change of solution? Give an equation. What two processes take place when an ionic solid dissolves? [4]
5. What is the enthalpy change of hydration. Give equation [2]
6. Explain the effect of ionic charge and size on (i) lattice enthalpy [6] and (ii) enthalpy change of hydration [6]
7. Give a definition of entropy [1]
8. Explain the difference in entropy of a solid and a gas [1], the change when a solid lattice dissolves [1] and the change in a reaction where there is a change in the number of gaseous molecules [1]
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!
1. What is the enthalpy change of atomisation. Give equation too [2]
2. WHat is the first electron affinity. Give equation too [2]
3. Wht is the standard enthalpy change of formation. Give equation too [2]
4. What is the enthalpy change of solution? Give an equation. What two processes take place when an ionic solid dissolves? [4]
5. What is the enthalpy change of hydration. Give equation [2]
6. Explain the effect of ionic charge and size on (i) lattice enthalpy [6] and (ii) enthalpy change of hydration [6]
7. Give a definition of entropy [1]
8. Explain the difference in entropy of a solid and a gas [1], the change when a solid lattice dissolves [1] and the change in a reaction where there is a change in the number of gaseous molecules [1]
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!
1)it is the entahply change when 1 mole of gaseous atoms is formed from its elements under standard condtions for example K+(g)+2Cl-(g) to give KCL2(s)
2)eletron affitinity is the addition of an electron to an atom in one mole of gaseous ions to form -1 gaseous ions under standard conditions for example cl2(g) gives cl-(g)
3)it is the enthalpy change when 1 mole of a substance is formed from its elements under standard condtions such as 100kpa,298K and 1mol dm-3 for example ch3oh+o2 gives co2+h20 so its c(s)+2h2(g)+1/2o2(g) gives ch3oh
4)entahlpy change of solution is the enthalpy change when one mole of ionic compound is dissolved compeleltly in water (aqueous solution)under standard conditions.Nacl(s) gives Na+ (aq) +cl- (aq), hydration of ions and breakdown of gaseous ions to give soltution
5)it is the enthalpy change when one mole of isolated gaseous ions forms one mole of aqueous solution under standard conditions for example Na+(g) + cl-(g) gives Nacl(aq)
how am i doing so far?
can anyone help me with 3d on this question, no idea what the MS is talking about
http://www.sci2.co.uk/chemistry/Chemistry%20Old%20Specification/A2/2816_01/2002%20Jun%20QP.pdf
MS
http://www.sci2.co.uk/chemistry/Chemistry%20Old%20Specification/A2/2816_01/2002%20Jun%20MS.pdf
http://www.sci2.co.uk/chemistry/Chemistry%20Old%20Specification/A2/2816_01/2002%20Jun%20QP.pdf
MS
http://www.sci2.co.uk/chemistry/Chemistry%20Old%20Specification/A2/2816_01/2002%20Jun%20MS.pdf
Original post by Robpattinsonxxx
Questions for you to answer.
MODULE 1
1. Describe how the concentration and half life changes with zero, first and second order concentration-time graphs.
2. Explain quanlitatively the effect of temperature change on a rate constant and rate of reaction.
3. How does the value of Kc change with increasing temperature when the forward reactions are (i) endothermic (ii) exothermic.
4. What does a value of Kc>1 indicate?
5. What is pKa?
6. What does Kw actually show you?
7. How can a buffer solution be made?
8. What are the approximate pH ranges of the indicators phenolphthalein, bromothymol blue and methy orange?
9. Describe how you can undertake an experiment to work out the enthalpy change of neutralisation.
As far as I know, apart from calculations, answering these will give you a broad view of module 1. I'm even going to answer them
MODULE 1
1. Describe how the concentration and half life changes with zero, first and second order concentration-time graphs.
2. Explain quanlitatively the effect of temperature change on a rate constant and rate of reaction.
3. How does the value of Kc change with increasing temperature when the forward reactions are (i) endothermic (ii) exothermic.
4. What does a value of Kc>1 indicate?
5. What is pKa?
6. What does Kw actually show you?
7. How can a buffer solution be made?
8. What are the approximate pH ranges of the indicators phenolphthalein, bromothymol blue and methy orange?
9. Describe how you can undertake an experiment to work out the enthalpy change of neutralisation.
As far as I know, apart from calculations, answering these will give you a broad view of module 1. I'm even going to answer them
I thought I'd give these a shot too, if that's ok
1. In zero order graphs, half life decreases as concentration decreases (ie over time). This is shown by a straight line with a negative gradient that is not steep (I've forgotten the opposite to the word steep...weird...shallow? haha). In first order graphs, half life is constant. This is shown by a curve (I would draw it in the exam... not sure what else to say for this one). In second order graphs, half life increases with time (as concentration decreases) Then i'd draw a diagram to show what the conc/time graph looks like.
2. When temperature increases, the rate constant increases and therefore the rate of reaction increases because the molecules gain more kinetic energy and therefore there are more frequent and successful collisions, so the rate of reaciton increases.
3. If the forward reaction is endothermic and the temperature increases then Kc increases. If the forward reaction is exothermic and the temperature decreases then Kc decreases.
4. Kc>1 means that the position of equilibrium is on the products side ie the equilibrium favours the products, greater yield of products.
5.pKa= -log (Ka)
6. Kw shows the balance between H+ and OH- concentrations? (not sure about this one...like what it actually shows...). Kw is the ionic product of water...
7. A buffer solution consists of a weak acid and it's salt. To make a buffer solution (there are a few different ways i think) you can react an excess of weak acid with an alkali so that the usual equilibrium is set up (HA --> H+ + A-)
and also then the salt dissociates so that there's a high concentration of the weak acid and it's salt. I also think you can just mix together a weak acid and it's salt to get a buffer solution.
8. phenolphthalein : roughly 8-10, bromothymol blue roughly 6-7.5, methyl orange roughly 2.5-4
9. I would mix 100cm3 of alkali with 100cm3 acid. I would measure the temperature at the start and end of the experiment to find delta T. Then I would figure out Q=mcdeltaT where m is 200cm3 (mass of solutions), c=specific heat capacity of water which is 4.18. Then I would divide Q by 1000 to get it in kj and then I would divide it again by the number of moles of water produced. Then I would put a minus sign in front of it as enthalply change of neutralisation is exothermic.
Original post by The Illuminati
does anyone know if there is a specific way (at A Level) that you are supposed to draw 3D diagrams. e.g. for a tetrahedral I always draw 2 thin lines (one at the top, 1 at the bottom) and 2 thick lines (sometimes dashed, sometimes filled in, sometimes not filled in). I ask because I lost marks on this question in F324 and I really don't think I should have. Got my paper back and my teacher said that it doesn't matter at A Level and I should have got the marks.
what?
they marked you down for that? Sounds harsh :/ i draw them like this :
http://www.google.co.uk/imgres?um=1&hl=en&client=firefox-a&sa=N&rls=org.mozilla:en-GB
fficial&biw=1252&bih=610&tbm=isch&tbnid=Uhh_Aht1za76wM:&imgrefurl=http://nrich.maths.org/6451/solution&docid=_eIGeM-xaLFdmM&imgurl=http://nrich.maths.org/content/id/6451/Tetrahedral.png&w=694&h=660&ei=nYLQT4WRMInD8QPb1JnADA&zoom=1&iact=hc&vpx=489&vpy=73&dur=119&hovh=219&hovw=230&tx=148&ty=153&sig=106960885784307837988&page=2&tbnh=133&tbnw=139&start=21&ndsp=25&ved=1t:429,r:15,s:21,i:177but without the pale blue lines of course
do we need to be able to use graphs for changes in gibbs free energy with temperature?
Original post by otrivine
1)it is the entahply change when 1 mole of gaseous atoms is formed from its elements under standard condtions for example K+(g)+2Cl-(g) to give KCL2(s)
2)eletron affitinity is the addition of an electron to an atom in one mole of gaseous ions to form -1 gaseous ions under standard conditions for example cl2(g) gives cl-(g)
3)it is the enthalpy change when 1 mole of a substance is formed from its elements under standard condtions such as 100kpa,298K and 1mol dm-3 for example ch3oh+o2 gives co2+h20 so its c(s)+2h2(g)+1/2o2(g) gives ch3oh
4)entahlpy change of solution is the enthalpy change when one mole of ionic compound is dissolved compeleltly in water (aqueous solution)under standard conditions.Nacl(s) gives Na+ (aq) +cl- (aq), hydration of ions and breakdown of gaseous ions to give soltution
5)it is the enthalpy change when one mole of isolated gaseous ions forms one mole of aqueous solution under standard conditions for example Na+(g) + cl-(g) gives Nacl(aq)
how am i doing so far?
2)eletron affitinity is the addition of an electron to an atom in one mole of gaseous ions to form -1 gaseous ions under standard conditions for example cl2(g) gives cl-(g)
3)it is the enthalpy change when 1 mole of a substance is formed from its elements under standard condtions such as 100kpa,298K and 1mol dm-3 for example ch3oh+o2 gives co2+h20 so its c(s)+2h2(g)+1/2o2(g) gives ch3oh
4)entahlpy change of solution is the enthalpy change when one mole of ionic compound is dissolved compeleltly in water (aqueous solution)under standard conditions.Nacl(s) gives Na+ (aq) +cl- (aq), hydration of ions and breakdown of gaseous ions to give soltution
5)it is the enthalpy change when one mole of isolated gaseous ions forms one mole of aqueous solution under standard conditions for example Na+(g) + cl-(g) gives Nacl(aq)
how am i doing so far?
1. Try again. Couple of mistakes.
2. Add a vital piece of info!
3. Missing vital piece of info again.
4. Check the last 5 words and edit.
5. How do the gaseous ions form aqueous ions?
Original post by Smiley Face :)
Ca(OH)2---> Ca2+ + 2OH-
Is that why u double conc of OH??
(i know u just explained this too me, sos, just trying to get it clear in my thick brain)
Is that why u double conc of OH??
(i know u just explained this too me, sos, just trying to get it clear in my thick brain)
You're not thick, I made the same mistakes many times. It's a trick in the question but yes it's right. It's better to understand WHY instead of just knowing it by the markscheme, it'll help a lot in the real paper.
Are these questions for everyone to answer?
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