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Author Topic: ALL CIE CHEMISTRY DOUBTS HERE !!  (Read 119196 times)

Offline Dania

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Re: CIE Chemistry doubts.
« Reply #135 on: October 29, 2010, 04:37:02 pm »
Can someone please help and explain this question for me?
Refer to the attachment.
Thanks in advance.
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Offline Deadly_king

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Re: CIE Chemistry doubts.
« Reply #136 on: October 29, 2010, 05:55:13 pm »
Quote from: Dania on October 29, 2010, 04:37:02 pm
Can someone please help and explain this question for me?
Refer to the attachment.
Thanks in advance.

The diagram represents a mass spectrum for HCl.

NOTE : Only positive ions produce peaks in a mass spectrum since the substance is initially bombarded with electrons such that it loses one electron from a shared pair or a lone pair due to collision.

Hence for part 1 => 35Cl+
Second answer is 1H37Cl+

As for the third part, we must use the relative abundance of the two isotopes and multiply them by the Ar of the respective isotope. Then the sum of these two values is divided by the total amount of substance, in terms of abundance.

Relative atomic mass of Cl = (75(35) + 25(37))/(75 + 25) = 35.5

Just showing the above equation should be enough to score all the marks ;)
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Offline Dania

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Re: CIE Chemistry doubts.
« Reply #137 on: October 30, 2010, 05:57:57 pm »
What would I get if I had to react these 2 organic compounds?
Please explain any substitutions and/or additions.
Thanks in advance.
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Offline Deadly_king

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Re: CIE Chemistry doubts.
« Reply #138 on: October 30, 2010, 06:13:05 pm »
Quote from: Dania on October 30, 2010, 05:57:57 pm
What would I get if I had to react these 2 organic compounds?
Please explain any substitutions and/or additions.
Thanks in advance.

That may depend on the conditions.

But the most appropriate reaction might be between the hydroxyl group of Y to the carboxylic group of Z to form an ester.

An alcohol reacts with a carboxylic acid to give an ester and water. Therefore it will be a condensation reaction whereby the H from alcohol and the OH from carboxylic acid combine to form water while the remaining compound joins together to give an ester. ;)
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Offline $!$RatJumper$!$

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Re: CIE Chemistry doubts.
« Reply #139 on: October 30, 2010, 06:23:27 pm »
Quote from: Dania on October 30, 2010, 05:57:57 pm
What would I get if I had to react these 2 organic compounds?
Please explain any substitutions and/or additions.
Thanks in advance.

Thats right, it would form an ester and water for sure
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Offline Dania

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Re: CIE Chemistry doubts.
« Reply #140 on: October 30, 2010, 08:54:40 pm »
Crap. Sorry about that. It's question 5 from May/June 2009 Paper 2, Variant 2. Please check it out and get back to me.
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Offline missbeautiful789

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Re: CIE Chemistry doubts.
« Reply #141 on: October 30, 2010, 09:58:09 pm »
Attached is the answer from the marking scheme.

It makes sence to work backwards from U.
Add an -OH and an -H to the alkene.....then your done

I can't explain the mechanism..if they say they react, then i believe them...i just know how to find the product

Aldehydes react with each other apparently.
« Last Edit: October 30, 2010, 10:02:02 pm by missbeautiful789 »
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Offline Deadly_king

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Re: CIE Chemistry doubts.
« Reply #142 on: October 31, 2010, 08:17:27 am »
Quote from: Dania on October 30, 2010, 08:54:40 pm
Crap. Sorry about that. It's question 5 from May/June 2009 Paper 2, Variant 2. Please check it out and get back to me.

Yeah..........you have only one choice here. You need to work back from U.

It has been said that T contains one OH group and form U, we may easily identify the presence of an aldeyde group. However it cannot be the conversion of a primary alcohol to an aldehyde since we can note that T has 2 oxygen atoms.

So it is bound to contain an OH group on one of the carbon carrying the C=C.

T is converted into U by using concentrated sulfuric acid which is a dehydrating agent and will cause the elimination of water from T top form U

Type of reaction : Elimination reaction or dehydration.

b) U contains two functional groups. You can name any one of them and identify them using the appropriate substance.

Example :
Alkene -----> It decolourises bromine.
Ketone -----> It gives an orange precipitate with 2,4 DNPH

Hope it helps :)
« Last Edit: October 31, 2010, 08:19:41 am by Deadly_king »
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Offline Dania

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Re: CIE Chemistry doubts.
« Reply #143 on: October 31, 2010, 01:23:44 pm »
Thank you, it did.
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Offline Aadeez || Zafar

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Re: CIE Chemistry doubts.
« Reply #144 on: November 01, 2010, 05:22:18 pm »
No more doubts frm u all
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Yeh BaaabuRaao ka style hein!

Offline Deadly_king

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Re: CIE Chemistry doubts.
« Reply #145 on: November 01, 2010, 05:33:12 pm »
Quote from: CambridgeDreamer on November 01, 2010, 05:22:18 pm
No more doubts frm u all

Why are you saying this?
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Offline Aadeez || Zafar

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Re: CIE Chemistry doubts.
« Reply #146 on: November 01, 2010, 05:59:47 pm »
Quote from: Deadly_king on November 01, 2010, 05:33:12 pm
Why are you saying this?

i think that i know much of the chemistry so can solve any doubts
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Yeh BaaabuRaao ka style hein!

Offline Deadly_king

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Re: CIE Chemistry doubts.
« Reply #147 on: November 02, 2010, 04:53:18 am »
Quote from: CambridgeDreamer on November 01, 2010, 05:59:47 pm
i think that i know much of the chemistry so can solve any doubts

Ooh...........glad to have members like you who are so interested to help. :)

But you'll have to be patient, wait for other members to post their doubts ;)
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Offline moon

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Re: CIE Chemistry doubts.
« Reply #148 on: November 02, 2010, 01:00:13 pm »
plz help me to solve this question. thanx in advance.

element         Atomic radius/pm               Ionic radius/pm

lithium                 152                              ??????
sodium                186                                 95
potassium            227                                138
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Offline Arthur Bon Zavi

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Re: CIE Chemistry doubts.
« Reply #149 on: November 02, 2010, 01:17:43 pm »
Quote from: moon on November 02, 2010, 01:00:13 pm
plz help me to solve this question. thanx in advance.

element         Atomic radius/pm               Ionic radius/pm

lithium                 152                              ??????
sodium                186                                 95
potassium            227                                138

43 - 7 = 36

Therefore 95 - 36 = 59 pm. IDK :D
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