OCR AS - Chemistry Unit F322 - Chains, energy and resource - REVISION!

LOL yeah I just figured out:P

I wanted to ask.... if you want to work out enthalpy change of formation, but have delta H values of Combustion.... DO THE arrows point up or down from the products when doing Hess's law?

The arrows would point down!
Because you would have:
btw , imagine 2 arrows, coming off both sides of the reaction (:

elements -----------> product ( which you're working the enthaly change combustion for) .
.
. +o2
.
\/
product which is the same for both combustions

get it?

(edited 13 years ago)

Reply 41

sa258

Hello, how is everyone revising for the fossil feuls, industrial importance, alocohols, greenhouse effect, ozone stuff etc because I find that stuff soooooooooooooo boring and when I come to reivse I just lose all my motivation.

Also if there's a really good revision book or text book that I could buy which would help me out? I've got the Heinemann one at the moment.

(edited 13 years ago)

Reply 42

J DOT A

Original post by gemstar!

The arrows would point down!
Because you would have:
btw , imagine 2 arrows, coming off both sides of the reaction (:

elements -----------> product ( which you're working the enthaly change combustion for) .
.
. +o2
.
\/
product which is the same for both combustions

get it?

Ahh brillaint! Got ya :smile:

And can someone help me draw (C2H5)3COH
the book says its 3-ethylpropan-3-ol.

How the **** did they get that?

Reply 43

SteveCrain

someone do question 2 b ii) on this paper and tell me what you get

http://pastpapers.org/AS/chemistry/HowFar/2001%20Jan%20QP.pdf

Reply 44

gemstar!

1

Original post by sa258

Hello, how is everyone revising for the fossil feuls, industrial importance, alocohols, greenhouse effect, ozone stuff etc because I find that stuff soooooooooooooo boring and when I come to reivse I just lose all my motivation.

Also if there's a really good revision book or text book that I could buy which would help me out? I've got the Heinemann one at the moment.

Oh my gosh, same!
I'm literally able to read like a page before my attention is else where :L

Reply 45

gemstar!

1

Original post by SteveCrain

someone do question 2 b ii) on this paper and tell me what you get

http://pastpapers.org/AS/chemistry/HowFar/2001%20Jan%20QP.pdf

It would be C8H18 (: did you get that?

Reply 46

gemstar!

1

Original post by J DOT A

Ahh brillaint! Got ya :smile:

And can someone help me draw (C2H5)3COH
the book says its 3-ethylpropan-3-ol.

How the **** did they get that?

Being propan, you would of thought it would be 1-ethylpropan-1-ol, but never mind :L
I think it would be drawn like this-
.......H
........l
....H-C-H
........l
....H-C-H
........l
OH-C-C-C

Excuse my drawing! Its so hard to draw on here :L

(edited 13 years ago)

Reply 47

g_sachdeva

hello everybody im revising unit 2 too and i was wondering if anybody has done the unit 2 mock because we have done it and i need to find the mark scheme to correct my answers the q was
describe and explain the factors that affect the rate of hydrolysis of halogenoalkanes

Reply 48

g_sachdeva

Original post by g_sachdeva

hello everybody im revising unit 2 too and i was wondering if anybody has done the unit 2 mock because we have done it and i need to find the mark scheme to correct my answers the q was
describe and explain the factors that affect the rate of hydrolysis of halogenoalkanes

it was a 7 mark q btw and guess wot i got ???
0/7 :mad:

Reply 49

Phenylethylamine_

Retaking this unit...I have unit 4 as well in the summer, which makes this unit super easy!

Reply 50

MsMedic

Original post by gemstar!

It would be C8H18 (: did you get that?

how did you come up with that answer?

Reply 51

gemstar!

1

Original post by MsMedic

how did you come up with that answer?

Ignore my answer, i didn't fully read the question :L

Reply 52

SteveCrain

Original post by gemstar!

Ignore my answer, i didn't fully read the question :L

nah you got it right

Reply 53

J DOT A

Original post by gemstar!

Ignore my answer, i didn't fully read the question :L

LOL you seem to be our teacher here!

How would you name this....

CH3CH2(BR)CH2CH2(Cl)CH3

What comes first? I never know...?

And here is another one...

CH3CH2(Cl)CH2CH2(I)CH2(F)CH3

Reply 54

CeeTay

2

Original post by gemstar!

Oh my gosh, same!
I'm literally able to read like a page before my attention is else where :L

not even covered it in lesson yet.. never mind revising it!

Reply 55

Contrad!ction.

15

Original post by J DOT A

LOL you seem to be our teacher here!

How would you name this....

CH3CH2(BR)CH2CH2(Cl)CH3

What comes first? I never know...?

And here is another one...

CH3CH2(Cl)CH2CH2(I)CH2(F)CH3

You name alphabetically, so it would be 2-bromo-4-chloropentane (I think)

I got 2-chloro-5-fluoro-4-iodohexane as the second.

I lost my teacher before Green Chemistry so no idea how I'm going to do that.

Reply 56

gemstar!

1

Original post by J DOT A

LOL you seem to be our teacher here!

How would you name this....

CH3CH2(BR)CH2CH2(Cl)CH3

What comes first? I never know...?

And here is another one...

CH3CH2(Cl)CH2CH2(I)CH2(F)CH3

Hahaa, I wish I had the knowledge of a chemistry teacher :tongue:

and what the person above me said, is right for your question (:

Reply 57

gemstar!

1

Original post by SteveCrain

nah you got it right

Ohh, yay :P
Well the Mr of Arcton 133 or whatever it is 118...this probably isnt accurate as im not referrirng back to that question :P
Anyway, and the Mr of C8H18 is like 114? and compared to the other compounds, that the most similar (: