Post by: superflya on February 03, 2010, 02:52:15 pm
this essay type questions are a pain :S
Post by: monokekie on February 03, 2010, 04:25:12 pm
to solve this:
we need to let the unknown hydrocarbon be
from the information given, we conclude that in the resultant 230ml gas, there are 60ml of
we then use the formula pv=nRT to find the number of moles of water and carbon dioxide produced , which yields n(
next, we use the same method to find the original mole number of the unknown hydrocarbon in the reactant gas.
which is n(
to find X, we find the ratio n(
to find Y, we find
following the previous step, we can determine that X is 6, and Y is also 6. so we get
Post by: superflya on February 03, 2010, 07:06:03 pm
can anyone clear it up?
Post by: monokekie on February 03, 2010, 08:13:53 pm
Post by: superflya on February 03, 2010, 08:25:55 pm
Post by: fady_22 on February 03, 2010, 08:36:20 pm
After you substitute all the values in given in the question, you get 0.00061 mol.
OK, now you have to find the ratio of the number of mole of each carbon and hydrogen to the hydrocarbon, to find how much MORE mole there is of carbon and hydrogen than the unknown hydrocarbon-- the ratio becomes 1:6 for both. This means that for every 1 mole of the hydrocarbon, there are 6 mole of carbon/hydrogen.
Therefore, the formula is C6H6.
Does that make any more sense?
Post by: monokekie on February 03, 2010, 08:38:15 pm
Since the question states that the hydrocarbon was burnt in excess oxygen, we assume that the unknown hydrocarbon is the only source of hydrogen and carbon in this reaction
The carbon and hydrogen atoms in water and carbon dioxide therefore only come from the hydrocarbon. When we find how many moles of carbon and hydrogen there are in the two products, we can thus divide each of them by the n of hydrocarbon initially present. So that we can find how many moles of each element corresponds to one mole of the hydrocarbon
Post by: superflya on February 03, 2010, 08:40:13 pm
Post by: superflya on February 08, 2010, 09:54:33 pm
and what primary form is lead(Pb) found in?
Post by: superflya on February 25, 2010, 12:16:56 am
anyone have like a list of common errors and there effects on the final results?
Post by: superflya on March 31, 2010, 01:42:46 pm
The hollow cathode lamp is pulsed with high current, causing a larger atom population and self-absorption during the pulses. This self-absorption causes a broadening of the line and a reduction of the line intensity at the original wavelength.
Post by: monokekie on April 02, 2010, 12:40:50 am
After absorbing the light energy, an atom would then release the quantum of energy, which sometimes emits light. In AAS, we want to know the amount of light absorbed by the atoms, but not the amount of light released by them. The light emitted may lead to biased experimental results. To eliminate the bias, the light is therefore chopped. So that less light released by the sample will be detected.
Post by: simonhu81292 on April 02, 2010, 12:52:47 am
yeah...thats when a monochromator comes handy ...
Post by: superflya on April 02, 2010, 04:49:13 pm
Post by: physics on April 02, 2010, 09:07:28 pm
wow ...totally correct!!!ahahahahahha :D ur a bit too late u smart noob LOL
yeah...thats when a monochromator comes handy ...
*__* u wish u were smart
anywho superflya good on you :D
Post by: simonhu81292 on April 02, 2010, 09:09:24 pm
yeah ....i will let kekie do the work ...
and i will do the clarifying ...
haha
Post by: superflya on April 04, 2010, 04:32:16 pm
Post by: Edmund on April 04, 2010, 05:07:26 pm
havnt finished unit 3 so im a lil confused, do we have to know about dienes?Well, they are just hydrocarbons with 2 alkene groups...
Post by: superflya on April 04, 2010, 05:17:15 pm
havnt finished unit 3 so im a lil confused, do we have to know about dienes?Well, they are just hydrocarbons with 2 alkene groups...
yea :P havnt seen a question in the heinemann book where it asks to name a compound with a diene..
Post by: Edmund on April 04, 2010, 05:23:55 pm
Then you don't have to name them ;Dhavnt finished unit 3 so im a lil confused, do we have to know about dienes?Well, they are just hydrocarbons with 2 alkene groups...
yea :P havnt seen a question in the heinemann book where it asks to name a compound with a diene..
Post by: longy1991 on April 04, 2010, 09:43:28 pm
Post by: superflya on April 04, 2010, 09:46:02 pm
eh, worth knowing. i reckon dichloroalkanes (or other dihaloalkanes) are probs the most likely out of any di family.
k sweet.
Post by: Blakhitman on April 04, 2010, 09:47:05 pm
I hate chem...so so so so so so so so so so much.
Post by: superflya on April 04, 2010, 10:30:49 pm
I haven't even started chem revision yet and holidays are almost over...
I hate chem...so so so so so so so so so so much.
revision? have u finished the unit?
Post by: Blakhitman on April 04, 2010, 10:32:24 pm
Post by: superflya on April 04, 2010, 10:37:40 pm
Post by: simonhu81292 on April 04, 2010, 10:40:24 pm
wow so close ..
reminds me that i need to study physics too ...
thanks ~~~
Post by: Blakhitman on April 04, 2010, 10:44:45 pm
7-8 weeks to the exam ;)
I know I know...I'll start tomorrow. I'm going fine with physics, been revising for that, cause it's fun.
ughh...I'll have to do some spec, nmr and all those gay things tomorrow too....
Post by: fady_22 on April 04, 2010, 10:54:16 pm
7-8 weeks to the exam ;)
I know I know...I'll start tomorrow. I'm going fine with physics, been revising for that, cause it's fun.
ughh...I'll have to do some spec, nmr and all those gay things tomorrow too....
Physics? Fun?
Post by: superflya on April 04, 2010, 10:57:54 pm
7-8 weeks to the exam ;)
I know I know...I'll start tomorrow. I'm going fine with physics, been revising for that, cause it's fun.
ughh...I'll have to do some spec, nmr and all those gay things tomorrow too....
Physics? Fun?
heaps better then chem.
Post by: fady_22 on April 04, 2010, 10:59:36 pm
7-8 weeks to the exam ;)
I know I know...I'll start tomorrow. I'm going fine with physics, been revising for that, cause it's fun.
ughh...I'll have to do some spec, nmr and all those gay things tomorrow too....
Physics? Fun?
heaps better then chem.
No!
Chem is awesome! :)
I hate physics. I regret choosing it now. Oh well...
Post by: Blakhitman on April 04, 2010, 11:00:24 pm
7-8 weeks to the exam ;)
I know I know...I'll start tomorrow. I'm going fine with physics, been revising for that, cause it's fun.
ughh...I'll have to do some spec, nmr and all those gay things tomorrow too....
Physics? Fun?
Way better than chem.
Post by: superflya on April 04, 2010, 11:06:58 pm
Post by: vexx on April 04, 2010, 11:11:36 pm
7-8 weeks to the exam ;)
I know I know...I'll start tomorrow. I'm going fine with physics, been revising for that, cause it's fun.
ughh...I'll have to do some spec, nmr and all those gay things tomorrow too....
Physics? Fun?
heaps better then chem.
No!
Chem is awesome! :)
I hate physics. I regret choosing it now. Oh well...
yay fady! someone else who agrees chem is awesome ha ha.
Post by: simonhu81292 on April 04, 2010, 11:12:38 pm
lol ...
Post by: Blakhitman on April 04, 2010, 11:13:45 pm
Please don't put the words fady, chem and awesome in the same sentence :D
Post by: superflya on April 04, 2010, 11:14:04 pm
getting better? as in getting into the biochem... more inclined towards the bio bit ?
lol ...
aha yea funnily enough, dispised 1/2 bio though ;D
Post by: vexx on April 04, 2010, 11:14:55 pm
Whenever fady is mentioned in a post I think it's me ><
Please don't put the words fady, chem and awesome in the same sentence :D
how come you think it's you :o
haha
Post by: Blakhitman on April 04, 2010, 11:15:37 pm
Whenever fady is mentioned in a post I think it's me ><
Please don't put the words fady, chem and awesome in the same sentence :D
how come you think it's you :o
haha
Because I share the same name as a chem lover :(...:D