needin some1 smart!! (1 Viewer)

[skool_angel]

okiez
can someone tell mi the answer to

-describe and account for the many uses of ethanol as a solvent for polar and non-polar substance?

wat do they mean by polar and non-polar substance??


and also
why do u need a catalyst to dehydrate and hydrate ethylene to ethene??

also last question
-identify the IUPAC nomenclature for stright-chained alkanols from c1 to c8?
do they mean methanol, ethanol, propanol etc.

 

[McLake]

Originally posted by skool_angel
describe and account for the many uses of ethanol as a solvent for polar and non-polar substance?

wat do they mean by polar and non-polar substance??

Polar - The OH bit is polar. This means that the electrons are unevenly shared across the covalent bond, making it "attractive" to other polar substances.
Non-polar - The C2H4 section is non-polar.

why do u need a catalyst to dehydrate and hydrate ethylene to ethene??

The catalyst (H2SO4) reduces the "activation energy" (the amount of energy needed to start the reaction), allowing the reaction to occur faster/at a lower temprature.

identify the IUPAC nomenclature for stright-chained alkanols from c1 to c8?
do they mean methanol, ethanol, propanol etc.

Yup.

 

[-=«MÄLÅÇhïtÊ»=-]

"-describe and account for the many uses of ethanol as a solvent for polar and non-polar substance?"

ethanol used as solvent because its polar behaviour can dissolve other polar substances (like dissolves like), and its hydrogen bonding allows it to be miscible wiv water.

The the C-OH in ethanol makes it polar. The O is electronegtive and C and H are electropositive. If u still dun get wat polar mean, read ur yr 11 shite



"why do u need a catalyst to dehydrate and hydrate ethylene to ethene?? "

ehtylene and ethene are the same thing, juz 2 different names. I fink u mean ethanol to ethene. Dun get them mixed up.
The syllabus specifically asks for the reason why catalyst is used, so a simple general explanation liek wat mclake gave i dun fink is wat they're after.

As i remember it:
Hydration of ethene to ethanol
Diluted H2SO4 is added to the ethene soln to produce ethyl hydrogen sulfate (sounds right to me). This then reacts with the H2O to form ethanol and the sulfuric acid is reformed again.

Dehydration of ethanol to ethene
The acid contains H+ ion which helps break the -OH and -H bonds in the ethanol to form ethene. Hence they use concentrated H2SO4, coz its got alotta H+ ions.

also last question
-identify the IUPAC nomenclature for stright-chained alkanols from c1 to c8?
do they mean methanol, ethanol, propanol etc. [/B][/QUOTE]

 

[Lord Ac]

Re: Re: needin some1 smart!!

Originally posted by -=MLhtʻ=-

As i remember it:
Hydration of ethene to ethanol
Diluted H2SO4 is added to the ethene soln to produce ethyl hydrogen sulfate (sounds right to me). This then reacts with the H2O to form ethanol and the sulfuric acid is reformed again.

Dehydration of ethanol to ethene
The acid contains H+ ion which helps break the -OH and -H bonds in the ethanol to form ethene. Hence they use concentrated H2SO4, coz its got alotta H+ ions.

[/B][/QUOTE]

Ok, we spend an ENTIRE PERIOD on this, throwing out theories to the teacher. At the end, he admitted thhat he himself didnt know. Thanks dudes, noow I can be smarter than him

Ac

 

[spice girl]

Re: Re: needin some1 smart!!

Originally posted by -=MLhtʻ=-
As i remember it:
Hydration of ethene to ethanol
Diluted H2SO4 is added to the ethene soln to produce ethyl hydrogen sulfate (sounds right to me). This then reacts with the H2O to form ethanol and the sulfuric acid is reformed again.

Dehydration of ethanol to ethene
The acid contains H+ ion which helps break the -OH and -H bonds in the ethanol to form ethene. Hence they use concentrated H2SO4, coz its got alotta H+ ions.

umm, jus some small corrections:
1) The double bond in ethene won't react with HSO4- because HSO4- is negatively charged and the double-bond is electron rich. Rather the double bond reacts with the H+, and then the thing reacts with the water, stealing the OH- to form ethanol.

2) Concentrated H2SO4 is a dehydrating agent, it will push the equilibrium reaction: C2H5OH <-> C2H4 + H2O towards completion to the right.

 

[Lord Ac]

Oh ...

Ac

 

[-=«MÄLÅÇhïtÊ»=-]

spicegal i remember reading my explanation from a book.
Wouldnt the dispersion forces between the HSO4- and ethene overcome the electron repulsion? Coz all bonds are electron rich.

for instance, when cyclohexene is reacted with bromine water (containing negatively charged Br ions) , the double bonds are broken.
But im not sure about doublre bonds and anions. Never been taught such a rule.


"Concentrated H2SO4 is a dehydrating agent, it will push the equilibrium reaction: C2H5OH <-> C2H4 + H2O towards completion to the right."
Yup, 4got that. But that's like an extra bonus. Not sole purpose why H2SO4 is used.

 

[skool_angel]

thanz i lot
man all of u r so smart
how did u go in ur chem hsc?

 

[McLake]

Originally posted by skool_angel
thanz i lot
man all of u r so smart
how did u go in ur chem hsc?

Tell you on the 19th ...

 

[skool_angel]

u r gettin ur uai on the 19th thats like nine days away

 

[-=«MÄLÅÇhïtÊ»=-]

results on 19th
uais on 20th

i hate chem! chem's....gay!

 

[spice girl]

In year 7, we had this madass teacher for science

one day, wot he did to demonstrate diffusion: he mixed a huge amount of ammonium with a base.

gofigure

 

[Lord Ac]

I dont get it ...

Ac

 

[spice girl]

well he managed to make enough ammonia to gas the whole lab and we had to evacuate....

 

[hgpstar]

sound suscpiciously like something my chem teacher would have done...

 

[utopian731]

Its so funny how a thread entitled "needin someone smart" gets 138 views

Chem accidents? Me an afriend created enough SO2 last year to wreck my throat for aweek (i was looking over it at the time) and to give the teacher NEXT DOOR an asthma attack that required hospitalisation

 

[t-i-m-m-y]

Originally posted by utopian731
Its so funny how a thread entitled "needin someone smart" gets 138 views

maybe cuz if u view the thread it makes u feel smart?

 

[freaking_out]

Its so funny how a thread entitled "needin someone smart" gets 138 views

just goes to show how much people think they are smart but probably not...

 

[spice girl]

no if you view the thread a number of times it counts towards the total as different views.

 

[elizabethy]

hey i think da answers r as follows:

ans1
ethanol- C2H5OH
the OH part is polar in nature n thus acts as a solvent ( a substance in which other substances dissolve) for polar substances

the hydrocarbon part is non polar in nature n thus acts as a solvent for the non polar substances.
thus it is mainly due to da structure of ethanol molecule dat it acts as a solvent for both polar n non polar substances.
n then u can give some examples like ethanol is used as a solvent for pharmaceutical pdts, food pdts n stuff, refer the excel for more examples

ans2
i agree with mclakes reason for the use of a catalyst, this is wat r teacher told us too!

ans3
ya they mean - methanol, ethanol n stuff

i hope this helps, mail me for any other help if needed!