Author Topic: ALL CIE CHEMISTRY DOUBTS HERE !!  (Read 122915 times)

Offline Deadly_king

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #225 on: November 16, 2010, 12:19:53 pm »
Energy at lower temperatures mean we take the graph with the higher peak and not the lower. Thus the answer is C and not D

Yupz........you are right.

I guess I was not very attentive  :-[

Anyway the higher the temperature the more particles will be having activation energy.

The number of particles is represented as the area after activation energy. In this case area is greater for the lower peak.

Hence at lower temperatures, the lower peak should be used. ;)

Offline Deadly_king

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #226 on: November 16, 2010, 12:22:21 pm »
understood, i thought of that too, but not so sure.Thanks! My friends are sitting for Bio on Thursday too.. I'm not  :P  Good Luck!

Anytime ;)

So you have only one more paper and it's an MCQ. ;D

Thanks :D

Offline $!$RatJumper$!$

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #227 on: November 16, 2010, 01:56:29 pm »
W05
12, (I get C. Why D)
15, (I get D)
16,
18,
24, (Why A and not C)
25, (I know it either A or D but cant choose which one)
30, (I dont see how this would be hydrolised)
31,
34,
36, (what does disproportionation mean)
39, (How are hydrocarbons oxidised in a convertor)
40 (What does optically active mean)

Thank you :)

Offline Deadly_king

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #228 on: November 17, 2010, 06:19:13 am »
W05
12, (I get C. Why D)
15, (I get D)
16,
18,
24, (Why A and not C)
25, (I know it either A or D but cant choose which one)
30, (I dont see how this would be hydrolised)
31,
34,
36, (what does disproportionation mean)
39, (How are hydrocarbons oxidised in a convertor)
40 (What does optically active mean)

Thank you :)

W0w.............all these doubts in only one paper. :o

Man, you should review your notes again.

Anyway i'll try to help but I might be taking some more time since am pretty busy today. I'll try as hard as possible. ;)

Offline $!$RatJumper$!$

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #229 on: November 17, 2010, 06:56:28 am »
W0w.............all these doubts in only one paper. :o

Man, you should review your notes again.

Anyway i'll try to help but I might be taking some more time since am pretty busy today. I'll try as hard as possible. ;)

Yeah some of us arent as clever as you guys hey :)
But thankx.. no worries if you're busy...
i got how to do Q16, 25, 30, 31 and 34 .. so no need for those :)

Offline Deadly_king

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #230 on: November 17, 2010, 08:07:33 am »
Yeah some of us arent as clever as you guys hey :)
But thankx.. no worries if you're busy...
i got how to do Q16, 25, 30, 31 and 34 .. so no need for those :)

It's not about being clever dude. You're going to have the same exams in 2 days, so you should have been ready. :)

Nov 05 p1

12. You just need to write the balanced equations for the complete combustion of one mole of each element.

Mg + 1/2O2 ----> Mg0

Al + 3/4O2 ----> 1/2Al2O3

S + 3/2O2 ----> SO3

Hence we can note that the number of moles of oxygen required increases but not constantly from Magnesium to Sulfur. ;)

Answer is D

15. You should first write the balanced equation representing the decomposition of the nitrate. That will be:

Ca(NO3)2 -----> CaO + 2NO2 + 1/2O2

From equation:
1 mole of nitrate gives 1/2 mole of oxygen gas.
164g of nitrate produces (24/2) dm3 of oxygen gas.
Hence 8.2g of nitrate will emit (12/164 x 8.2) = 0.6dm3 = 600cm3

Answer is C

19. Chiral centres are shown by a carbon atom carrying 4 different group of atoms. No carbon involved in a C=C will be able to show chirality.

Hence this leaves us with only two chiral centres. Starting from the right, they are the second and the third carbon atom

Answer is B

24. I'll proceed by elimination.

Propan-2-ol and 2-methyl-propan-2-ol are first to be rejected since they can form only one type of alkene due to free rotation. ;)

2-methylbutan-2-ol can form only 2 types of alkenes due to free rotation. It is connected to three other carbon atoms and should have been able to form 3 alkenes but two of them are identical.

Butan-2-ol should have formed only two types of alkenes but one of them show cis-trans isomerism. Hence it forms 3 types of alkenes.

Answer is A.

36. A reaction in which the same element is both oxidized and reduced is called a disproportionation reaction.

Is that enough or should I go in more details?

39.

Unburnt hydrocarbons are made to burn completely to form carbon dioxide and water. Hence this is a form of oxidation. Oxygen comes from the oxides of nitrogen which in turn gets reduced. ;)

« Last Edit: November 17, 2010, 09:57:14 am by Deadly_king »

Offline $!$RatJumper$!$

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #231 on: November 17, 2010, 09:30:41 am »
Thankx a ton for the help buddy! :)
I understood all that you mentioned.. but i think you did no 19 instead of no 18 :)

If you have time please do it, otherwise its fine. Thankx again +rep

Offline Deadly_king

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #232 on: November 17, 2010, 09:56:10 am »
Thankx a ton for the help buddy! :)
I understood all that you mentioned.. but i think you did no 19 instead of no 18 :)

If you have time please do it, otherwise its fine. Thankx again +rep

Anytime ;)

Ooh yeah.......I'm sorry for the confusion.

18. CaO is a basic oxide while ammonium sulfate is some kind of acidic as H+ can be liberated from NH4+. So they'll react together to give off ammonia, which being a gas will rise into the atmosphere. Hence the soil will lose its nitrogen which is required by plants.

Answer is C.

Offline $!$RatJumper$!$

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #233 on: November 17, 2010, 10:01:33 am »
Thank You :)

Offline Hypernova

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #234 on: November 17, 2010, 10:13:13 am »
+ rep DK for all of that
Ya Allah! Make useful for me what You taught me and teach me knowledge that will be useful to me.

Offline $!$RatJumper$!$

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #235 on: November 17, 2010, 09:37:05 pm »
S06 Q 10, 12, 17, 21, 25

Thank you kindly :)

Offline birchy33

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #236 on: November 18, 2010, 01:04:56 am »
You guys have been terrific and I hate to bundle you with more questions  ... but  ;D
O/N 09 QP1 variant 2

Q20
Q23
Q27

and to my much embarrassment ... Q1: I know its either A or D but I've completely forgot how to pick which one.

Cheers brudas.

Offline Master_Key

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #237 on: November 18, 2010, 06:32:18 am »
You guys have been terrific and I hate to bundle you with more questions  ... but  ;D
O/N 09 QP1 variant 2

Q20
Q23
Q27

and to my much embarrassment ... Q1: I know its either A or D but I've completely forgot how to pick which one.

Cheers brudas.

O/N 09 QP1 Variant 2.

Q1. Answer is D.

It is because 0.2 Moles of HC burn to give 35.4 g of CO2.

So, RFM of CO2=(12+(16*2)=44 g.

35.4/44 = 0.8

0.8 = 0.2
?    = 1

0.8/0.2=4

This is the simplest method. We get 4 Carbon atoms in one molecule of HC.

Do the Same with Water and we will get 8 Hydrogen atoms.

So the formula is C4H8

Offline Master_Key

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #238 on: November 18, 2010, 06:38:19 am »
You guys have been terrific and I hate to bundle you with more questions  ... but  ;D
O/N 09 QP1 variant 2

Q20
Q23
Q27

and to my much embarrassment ... Q1: I know its either A or D but I've completely forgot how to pick which one.

Cheers brudas.

O/N 09 QP1 Variant 2.

Q23. Answer is A.

The diagram shows 2 double bonds between C=C atoms. These are the bonds which are broken and Hydrogen or Bromine added. The C=O will not break. Both the double bonds break and form a single bond C-C. 2 Hydrogen atoms are bonded with two Carbon atoms. There are four carbon atoms so 4 Hydrogen atoms.

This gives to 2 moles of both substances as both exist as diatomic molecules.

elemis

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #239 on: November 18, 2010, 06:48:29 am »
S06 Q 10, 12, 17, 21, 25

Thank you kindly :)

Question 17

Chlorine displaces Iodine from the salt. So the Iodide anions lose electrons to chlorine i.e. they are oxidised.