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

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Thank You!

I answered a question for you that posted up before btw

Oh yeah but i think you were looking at the wrong question i wanted 3d, i think you were talking bout 3c....thanks anyway :h:

Reply 941

LifeIsGood

Original post by The Illuminati

Oh yeah but i think you were looking at the wrong question i wanted 3d, i think you were talking bout 3c....thanks anyway :h:

Oh my bad, sorry about that :redface:

I kind of get it, I don't know why the pH increases though :s-smilie:

If you had more CH3COONa you're adding more OH- theoretically so the H+ should remove it but the marking scheme says it's the other way around :s-smilie:

It is confusing.

Reply 942

Robpattinsonxxx

Module 3 questions now? :smile:

Reply 943

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 :smile:

(edited 11 years ago)

Reply 944

otrivine

hi can someone please explain to me in the book for the multi step reaction they gave example how did they get the NO3 as intermediate ?thanks

Reply 945

Robpattinsonxxx

NO3 is made in the 1st step but used up in the second step. Its just a molecule that you don't need in the overal equation.

Reply 946

otrivine

Original post by Robpattinsonxxx

NO3 is made in the 1st step but used up in the second step. Its just a molecule that you don't need in the overal equation.

but like how you know ? cause no2 + no2 gives n2o4 ?

Reply 947

niaghez

Original post by The Illuminati

25+75=100 therefore HCl makes up a quarter of the entire mitxure (25/100=1/4) so divide the original (undiluted) concentration by 4 then use the pH=-log[H+] calculation with this new conc.

:smile:

arghh i would never have come up with that method of doing it! and this may sound stupid but which paper is that?

Reply 948

Robpattinsonxxx

Original post by otrivine

but like how you know ? cause no2 + no2 gives n2o4 ?

Think it in this way. The products on the right hand side of the arrow must equal the products on the right hand side of the arrow in the overal equation. If you look in your book. You have to form an NO on the right hand side which you do in step one. that leaves you with the intermediate as I've mentioned before. You also need a co2 in the overal equation which you form in the second step. So you got the NO and CO2 that you need and the NO3 is used up in the second step. THat leaves you with NO2 formed in the second step also but this cancels with one of the NO2 on the LHS of the 1st step which is ionic as you only need one NO2 on the LHS of the overal equation.

I prob just made things worse now. Its hard. You have to stare at it for ages and try work it out like i did..

Reply 949

LifeIsGood

Original post by niaghez

arghh i would never have come up with that method of doing it! and this may sound stupid but which paper is that?

June 2010 I think for Unifying Concepts

I hate this unit, so hard.

Reply 950

Robpattinsonxxx

I prefer this unit. F324 is a bore lol

Reply 951

Oromis263

Original post by otrivine

hi can someone please explain to me in the book for the multi step reaction they gave example how did they get the NO3 as intermediate ?thanks

For a multi-step reaction, where it asks you to suggest the steps taken in a reaction, as long as your intermediates cancel, your first step involves the molar ratios specified by the rate equation, and you produce/use the right moles of everything else, they accept it.

Reply 952

niaghez

Original post by LifeIsGood

June 2010 I think for Unifying Concepts

I hate this unit, so hard.

oh right! havent done that yet lol.. its on the pile! hahaa. so is this your first time doing it??

Reply 953

LifeIsGood

Original post by Robpattinsonxxx

I prefer this unit. F324 is a bore lol

I like this unit better but the papers are quite difficult. I think January 2012 is the easiest paper there, I'm terrified of this unit :frown:

Reply 954

LifeIsGood

Original post by niaghez

oh right! havent done that yet lol.. its on the pile! hahaa. so is this your first time doing it??

Yep

I'm absolutely bricking it after looking at some of the questions

Reply 955

Robpattinsonxxx

I did jan 2012 and found it hard :frown:

got a c. had a's last year :'( so resiting this. its not that bad tho. def revise e.c of solution/hydration that lark. :smile:

Reply 956

chemicalX

Original post by otrivine

but like how you know ? cause no2 + no2 gives n2o4 ?

ok you start :biggrin:

Reply 957

otrivine

Original post by chemicalX

ok you start :biggrin:

was that correct though homeobox genes?

ok

Suggest two process that might be used to obtain hydrogen gas (2)

Reply 958

niaghez

Original post by LifeIsGood

Yep

I'm absolutely bricking it after looking at some of the questions

im retaking this and i still find it so hard! even the jan 2012 paper which is supposedly the easiest had a few hard calculations! its really impossible to practice every type of question because the calc questions can be almost anything :unimpressed:

(edited 11 years ago)

Reply 959

chemicalX

Original post by otrivine

was that correct though homeobox genes?

ok

Suggest two process that might be used to obtain hydrogen gas (2)

yes that was correct :

1) burning of a hydrogen rich gas such as methane/methanol
2) electrolysis of water to separate h2 and 1/2o2

describe 2 limitations of hydrogen fuel cells? (2)