Chemistry

Lantis

Damn gorgeous exam. The stuff I didn't do I had no clue of (Q10, argh) but the stuff that I did do was dead simple.

munkeehaven

youre lucky..im in the throes of depression...it wasnt that i found it hard but there were itsy-bitsy bits that i TOTALLY f ucked up. i did qts and bits i would leave out till the end...not a good idea..........and itsy bitsies add up......

PrecariousNuts

Bangbeater, I got the same answer... nice work.

Yeah that experiment is not only not mandatory but its also not even a demostration. I just waffle about the intermediate theory instead.

I got 70%

Q9 0.401...

For Q7 was the carboxylic acid ethanoic or propanoic?

munkeehaven

please tell me what was 8d?:(

i think it was propanoic thats goes from propanol to propanone to propanoic using nickel and h* ion right???

CuLT

Got the same answers as you for Q6 and on the %Fe.

I put down propanoic, my mind was tormented at that stage .

uary

For Q6 - I got heat of formation of methane to be 75.6 kJ mol-1
Any1 else get that??

I got that!


4 h What is percentage by mass of iron in iron oxide Fe3O3?

I got 70 %
as molecular mass is 160 and iron adds up 112 divided by 160 multiply by 100.

munkeehaven

i know that you can when you oxidise a secondary alco it goes to a ketone so it would be the opp for reduction...? man i rushed that qt....


anyone work out the ideal gas equation qt???

PrecariousNuts

Want me to make out some answers? I did all the questions as usual

BangBeater

Wat did ye all get for the Kc value- Q9 Part (e)?

claire h

Originally posted by munkeehaven
THE MOLAR VOLUME FOR GAS was wrong it said 24 but it should BE 22.4!!!!

22.4 L at s.t.p. It's 24 L at room temperature - which is what the question asked for. (Evil.)

If that isn't a mandatory experiment then maybe they'll do what they did the last time they asked something that wasn't on the course and just give the 18 marks for whatever you have down. *crosses fingers*

munkeehaven

go ahead and calm my tortured mind pleez

BangBeater

Do please!

munkeehaven

that was bloody harsh i thought they had made a misprint...i have NEVER come across 24 used in a qt.......

BangBeater

That's fckin crap - the 22.4l thing being written as 24 litres

I, and probably every other leaving cert student have spent the last 2 years USING 22.4L!!!! WHY CHANGE IT?????


ARSE!

A Big one....!

c0rk3r

i put down 69.9%, didnt round up the molecular mass.

classical studies will make or break my first choice!! DUN-Dun-dun!

BangBeater

Yera, tis prob worth about 3 marks i'd say. Nothing to get too panicy about

Still, very, very, lethal thing to do

penguincakes

It was -75.6 I think cause I got CH4 -> C + 2H2 /\H = 75.6, which you have to then change around. Or maybe I just ****ed up the signs.

Anyway, decent paper, I did all the qs cept for #1 which I forgot how to.

Yeah 70% for the iron, 90% for ...something else.


And they didn't get the molecular volume wrong, read it it says ROOM temperature, which is not STP. Though they didn't give STP which was ****ing stupid of them.

Q7 carboxylic was propanoic cause there's 3 carbons.
Now I'm not so sure about the types of reactions in 7, but here's mine:

(a) CH3 / CH2 are tetrahedral, C=O is planar.

(b) Methanol & propanoic acid. Condensation reaction.

(c) i Propanoic
ii Propanal CH3CH2CHO
iii 1: elimination reaction / dehydration reaction
2: addition reaction
iv Sodium dichromate, sulfuric acid


Err I'll do the rest later.

munkeehaven

they should have stated why they did that probably confused everyone ...and i thought that avogadros law specifically says its 22.4 for all gases under same conditions of temp and pressure....that qt put me right of and i was getting really nervous

uary

How are heavy metals removed from industrial waste,?
and
State one use of benzoic acid, i said used in as soap ingedinent?

penguincakes

Originally posted by BangBeater
Wat did ye all get for the Kc value- Q9 Part (e)?

1/36, not sure about that though. It was either that or 1/2.

PrecariousNuts

Q1
eriochrome black t
red to blue

d(i) .00081M
(ii) .081g/L
(iii)81ppm

Q4
h 70%

Q6
-75.6

Q9
e 0.401 I believe

Q10
a
(i) something huge like 24.86
(ii) 1306g 1.3kg
(iii) 276L

c
something by 10E-4 m^3

Q11

2.43?

penguincakes

Originally posted by uary
How are heavy metals removed from industrial waste,?
I did chemistry alone in the exam hall just me around 100 chairs and tables and examnier guy.
State one use of benzoic acid, i said used in as soap ingedinent?

I said sedimentation for heavy metals, & creation of toluene for benzoic acid

munkeehaven

penguincakes are you sure you are right about the propanoic because isnt it when you oxidise a secondary alcohol you always get a ketone?? so shouldnt you use a reduction to do the opposite??

BangBeater

Benzoic Acid - Used for the purposes of Chemistry.....(nice try!)....

Heavy Metals are taken out by some kind of precipitation technique

munkeehaven

precipation for heavy metals using aluminium sulphate

benzois acid is used for food preserving

munkeehaven

how did u get ii) .081g/L
(iii)81ppm
isnt grams=moles by Mr ie 83 for CaCO3?

BangBeater

How do you actually do Q9 (e)??

uary

cool,i think i got it right i said a flucinating agent is added eg. aluminum sulfate and allowed to settle,heavy ions fall to bottom and removed

munkeehaven

what qt is that? i threw out the paper as soon as possible

c0rk3r

Could someone write out Q6 (a) please,its annoying the hell out of me.

PrecariousNuts

Doesnt CaCO3 = 40 + 12 + 48 =100g?

BangBeater

6.0 moles of N2 and 18 moles of H2 initially.
Then, 6 moles of ammonia at equib.
In a 5 litre vessel.

uary

mr of caco3 is 100,

Q9 mate,if i knew how to do that i would have slept better last 2 years,
its impossible,i never can do it,
just doesnt make sense,
learning it now is not going to make a difference.

munkeehaven

ooh ****!! i wasnt looking at the right element...:(

BangBeater

Heat Of Formation - Heat change when a compound is formed from its elements in their standard states

Octane No. is a measure of the tendancy of a fuel to resist knocking


Hang on, shud the word 'One Mole' be in the def. for Heat Of Formation?

uary

Originally posted by munkeehaven
what qt is that? i threw out the paper as soon as possible

if your asking about the heavy metals then its Q4 f

Q9e is is the equlibrium question , Kc and all that

munkeehaven

yaa...oh my gawd this forum is just making me see hw much i got wrong.......HELLLPP!!!

c0rk3r

Originally posted by BangBeater

Hang on, shud the word 'One Mole' be in the def. for Heat Of Formation?

Yeah it should

penguincakes

Originally posted by munkeehaven
penguincakes are you sure you are right about the propanoic because isnt it when you oxidise a secondary alcohol you always get a ketone?? so shouldnt you use a reduction to do the opposite??

It's not a secondary alcohol though.

  H H O
  | | ||
H-C-C-C-O-H
  | |  
  H H

+

  H
  |
H-C-O-H
  |
  H

=

  H H O   H
  | | ||  |
H-C-C-C-O-C-H
  | |     |
  H H     H

(****in 20 edits later & it's alrightish lookin...

munkeehaven

it was raining this morning...i knew it was a bad omen....im so pissed off---- i thought i was good at chemistry--- ive never had a problem ---and now i FU CK up at the most crucial moment...MURPHYS LAW anyone??

munkeehaven

i dont mean the alcohol in the ester--methanol--i mean the one that can be ade to a ketone---propanol

penguincakes

Originally posted by munkeehaven
i dont mean the alcohol in the ester--methanol--i mean the one that can be ade to a ketone---propanol

There's no propanol, cause for an ester you need a COOH. Which you can't have in the middle of a chain.

CuLT

Precarious, are you quite sure the answer to the /_\H was -75.6 and not +75.6 ?

I was under the impression that it was -966 +75.6 to get the -890.4

c0rk3r

Originally posted by CuLT
Precarious, are you quite sure the answer to the /_\H was -75.6 and not +75.6 ?

I was under the impression that it was -966 +75.6 to get the -890.4

Thank You! was sweating for a moment there.I got the same as above.

12marks = 3%

munkeehaven

NOT THAT remember the qt asked what could the carboxylic acid be derived from--propanoic acid---

PrecariousNuts

I thought that heat of formation was nearly all the time negative

BangBeater

It HAS to be -75.6 - IT's exothermic

CuLT

Originally posted by c0rk3r
Thank You! was sweating for a moment there.I got the same as above.

12marks = 3%

heh np .

Though too bad I forgot the f*cking ratio for the edta question, I put it as 1:2 . I am BONED and GRILLED for that question now.

munkeehaven

I thought that heat of formation was nearly all the time negative

it wont be negative if the reaction is endothermic ie takes in energy

but for methane its exo

penguincakes

Originally posted by munkeehaven
NOT THAT remember the qt asked what could the carboxylic acid be derived from--propanoic acid---

Oh right. Well what are you asking? There's still no secondary alcohol. It's propan-1-ol -> propanal -> propanoic acid.