Author Topic: Chemistry p1(NIGHTMARE) Coming  (Read 10759 times)

Offline s16

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #30 on: June 10, 2009, 02:00:02 am »
November 2007 paper 1 q9 .. HOW DO YOU DO IT ??? :-[

Offline s16

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #31 on: June 10, 2009, 02:08:37 am »
Plz any1 ?

Offline khi2ruh

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #32 on: June 10, 2009, 02:22:27 am »
Plz any1 ?
im not sure if u do it this way but it worked for me
if u luk at the half equation SO32- becomes SO42-, this means it is getting oxidised by one oxygen atom hence the metal ion would get reduced to the same degree and a decrease in oxidation number would occur and +3-1=+2

Offline kimlasmay

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #33 on: June 10, 2009, 03:17:49 am »
Hey guys I just sat for the paper...

There were a lot organic Qs...More than 20...Inorganic also...Study about solubility...About halogens...Function of Bromide...Study about Astatine...Read a lot of past year Questions...Cis-trans stuff...

What reacts with sodium,NaHCO3...

REaction of ammonium ions...Thermal stability of H and halogens bonds...

Bond angles of organic cmpds...

Enthalphy change....

chiral centre...

FOCUS ON UR ORGANICS...

Offline aiyo12345

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #34 on: June 10, 2009, 03:35:41 am »
wait
how do we know he/she/it is telling the truth?
it could be that ihateteachers motherf**cker again  >:(

Offline slammer951

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #35 on: June 10, 2009, 03:44:57 am »
Can anyone help me with this question?

30) Use of the Data Booklet is relevant to this question.
Ethyl ethanoate can be obtained from ethanoic acid and ethanol by the following reaction.
CH3CH2OH + CH3CO2H = CH3CO2CH2CH3 + H2O
Ethanol (30 g) and ethanoic acid (30 g) are heated under reflux together, and 22 g of ethyl
ethanoate are obtained.
What is the yield of the ester?
A 25 % B 38 % C 50 % D 77 %

This is question 30 , November 08
« Last Edit: June 10, 2009, 03:46:38 am by slammer951 »

Offline s16

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #36 on: June 10, 2009, 03:46:26 am »
thank u for answering my qs..

Offline aiyo12345

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #37 on: June 10, 2009, 03:53:06 am »
Quote
Can anyone help me with this question?

30) Use of the Data Booklet is relevant to this question.
Ethyl ethanoate can be obtained from ethanoic acid and ethanol by the following reaction.
CH3CH2OH + CH3CO2H = CH3CO2CH2CH3 + H2O
Ethanol (30 g) and ethanoic acid (30 g) are heated under reflux together, and 22 g of ethyl
ethanoate are obtained.
What is the yield of the ester?
A 25 % B 38 % C 50 % D 77 %

This is question 30 , November 08

The answer would be C - 50%.
You have to calculate the moles of both ethanol and ethanoic acid and take the smaller value.
(since they react in 1:1 ratio, one with more moles would be in excess)
the aformentoned value of moles would equal the theoretical yield of ester in moles
(as again, they are in one:one ratio i.e. one mole of ethanoic acid reacts with one mole of ethanol to form one moles of ester)
then you can multiply RMM of ester given to the mole given to find theoretical yield in mass.
you then divide actual yield by theoretical yield.

Hope this helps  ;)
Meh if it doesn't.

Offline slammer951

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #38 on: June 10, 2009, 03:59:45 am »
Thanks for the help   ;D

Offline khi2ruh

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #39 on: June 10, 2009, 04:05:36 am »
can anyone please help me with Q4 Of nov08?

Offline khi2ruh

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #40 on: June 10, 2009, 04:06:39 am »
...and nov 04 Q10

Offline hira

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #41 on: June 10, 2009, 04:13:34 am »
anyone solved the paper?

Offline kimlasmay

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #42 on: June 10, 2009, 04:49:05 am »
I've done the paper 2 hours ago...The paper was fine..trust me....Its way more better than paper 2...

Offline MichelG

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #43 on: June 10, 2009, 04:55:48 am »
I've done the paper 2 hours ago...The paper was fine..trust me....Its way more better than paper 2...
I hope its easy....but can u tell me what to focus on most?? what was the main topic?? what were the hard questions about

Offline kimlasmay

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Re: Chemistry p1(NIGHTMARE) Coming
« Reply #44 on: June 10, 2009, 05:00:14 am »
The hard questions were in organic chemistry.....

The was more than 20 organic chemistry....