OCR A2 Chemistry Unit 5, F325 15th June 2015

Reply 60

ShadabAhmed

Original post by TheNoobishKnight

What do you mean?

x?

wat

idk

Reply 61

TheNoobishKnight

14

Original post by ShadabAhmed

x?

wat

idk

you said 'joke'? lol idk -_- :biggrin:

Reply 62

ShadabAhmed

Original post by TheNoobishKnight

you said 'joke'? lol idk -_- :biggrin:

i agreed that it was a joke lel kek

Can you guys please stop doing this mega quote -_-

Reply 66

kimhema68

Hi Guys,

Does anybody know any websites or PDF files where there are exam styles questions for OCR F325 Chemistry where the questions are arranged according to each modules?

Any help would be much appreciated.

Thanks

bump

Original post by kimhema68

Hi Guys,

Does anybody know any websites or PDF files where there are exam styles questions for OCR F325 Chemistry where the questions are arranged according to each modules?

Any help would be much appreciated.

Thanks

If only there was... I don't think there is, I wish there was.

You've got to go through the papers and find the question that you want to answer. TBH, for f325 that's not that hard. I think legacy papers 2816 also has questions for it too, but there are others also.

Reply 69

games211

16

Original post by TheNoobishKnight

If only there was... I don't think there is, I wish there was.

You've got to go through the papers and find the question that you want to answer. TBH, for f325 that's not that hard. I think legacy papers 2816 also has questions for it too, but there are others also.

f325 isnt hard :frown:

how are you revising for it and with what resources?

Reply 70

TheNoobishKnight

14

Original post by games211

f325 isnt hard :frown:

how are you revising for it and with what resources?

F325 certainly is at least challenging but I meant looking for the specific question such as buffers or Kc and that stuff is pretty easy in the past papers. I just Past papers and I make notes on the main points and practise, TBH, I did pretty badly at it in AS (got a D) so I shouldn't really be one telling giving you advice lol, it was my weakest subject -_-. Got to work hard this year and get it up to an A(with retakes of course).

I never used past papers last year but already I can see how important they are and should be the main focus of the revision regime and to memorise the mark scheme is also important(such as buffers, the 5-7 markers almost always ask for the same thing, so far for me at least).

Reply 71

twisted

10

Need some help here

NH3 + H2O --> NH4+ + OH-

Since ammonia is a weak base it only partially dissociates, what I don't understand is how if it dissociates does it gain a proton?

even though the dissociation is slight why is there a proton gain?

This makes no sense to me and I'm stuck here, would greatly appreciate some help right now as I am self teaching, thank you

Reply 72

serendipity-

Original post by kimhema68

Hi Guys,

Does anybody know any websites or PDF files where there are exam styles questions for OCR F325 Chemistry where the questions are arranged according to each modules?

Any help would be much appreciated.

Thanks

A-level chemistry is a website my sister always referred to.

http://www.a-levelchemistry.co.uk/OCR%20Chemistry%20A/OCR%20Chemistry%20A%20home.html

Reply 73

serendipity-

Original post by twisted

Need some help here

NH3 + H2O --> NH4+ + OH-

Since ammonia is a weak base it only partially dissociates, what I don't understand is how if it dissociates does it gain a proton?

even though the dissociation is slight why is there a proton gain?

This makes no sense to me and I'm stuck here, would greatly appreciate some help right now as I am self teaching, thank you

Since its a base, it accepts protons. You were taught that bases accept protons, right? On the pH table, water would technically be more acidic than ammonia because it has a lower pH so water donates a proton.

Reply 74

twisted

10

Original post by serendipity-

Since its a base, it accepts protons. You were taught that bases accept protons, right? On the pH table, water would technically be more acidic than ammonia because it has a lower pH so water donates a proton.

why would that make it a weak base then

Reply 75

serendipity-

Original post by twisted

why would that make it a weak base then

Generally it's a weak base but in this case it has to accept the proton because water has a lower pH than it.

If the equation comprised of two weak bases, the one with the higher pH would accept the proton and the one with the lower would donate.

What I'm trying to say is; even though ammonia is weak, in this equation, it's a stronger base that H20 due to the pH so it accepts it.

(edited 9 years ago)

Reply 76

twisted

10

Original post by serendipity-

Generally it's a weak base but in this case it has to accept the proton because water has a lower pH than it.

If the equation comprised of two weak bases, the one with the higher pH would accept the proton and the one with the lower would donate.

What I'm trying to say is; even though ammonia is weak, in this equation, it's a stronger base that H20 due to the pH so it accepts it.

I still don't understand how it dissociates

Reply 77

serendipity-

Original post by twisted

I still don't understand how it dissociates

Bases gain protons during their reaction with water. They don't act similarly to acids, which gives up protons.

Reply 78

TheNoobishKnight

14

Original post by twisted

I still don't understand how it dissociates

I am guessing because NH3 is weaker than H20, it gains the H+.
Very odd though, I guess going with the bronsted lowry theory, water is an acid as it donates the H+ ion.