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Danish
05-15-2005, 10:09 PM
:sl:
I created this specially for us Chemistry ppl. Anyway, i follow OCR, and any1 has practical exam coming up soon?

Well,this thread is just for discussion of chemistry. Help with chem, etc

I have a go, any1 know this:

A titration was carried out using an 0.10 moldm-3 solution of an unknown acid, HxA to determine the value of ‘x’ in the acid formula. 25 cm3 of 0.15 moldm-3 sodium hydrogen carbonate solution was found to require an average titre of 12.35 cm3 of acid to just neutralise it. What is the value of x?

Well, the answer is this:
1. Amount of sodium hydrogen carbonate = 3.75 x 10-3 mol,
ratio is 1:1, so amount H+ = 3.75 x 10-3 mol
H+ is 0.3 moldm-3, so x=3

any idea how they got that? :zip:
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Ibn Syed
05-15-2005, 10:35 PM
Nope
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Ra`eesah
05-16-2005, 06:03 PM
Assalamu'Alaykum

Molar concentration of the acid was 0.1M, yet it react as if it was 0.3M - the only possible explanation is that it contains three protons per particle.

hope that clears it up for u
Reply

Ibn Abi Ahmed
05-16-2005, 06:04 PM
:sl:

Chemistry is the subject i hate most. its just toooooo hard,, but good topic Mashallah:)
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Ibn Abi Ahmed
05-16-2005, 06:06 PM
Originally Posted by 3washey
Assalamu'Alaykum

Molar concentration of the acid was 0.1M, yet it react as if it was 0.3M - the only possible explanation is that it contains three protons per particle.

hope that clears it up for u
did you know you sounded just like a College proffesor ???? (no sarcasm) :)lol
Reply

Unique
05-16-2005, 06:22 PM
Lol...I'm doing A2 Chemistry, I think its quite hard, probably because I really dont like it. Anyway, I'm so glad I've got my CW out of the way... I just thought I'd express my relief!!! :D

Wassalam
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Danish
05-16-2005, 06:22 PM
Molar concentration of the acid was 0.1M, yet it react as if it was 0.3M - the only possible explanation is that it contains three protons per particle.
:sl:
sorry,but have absolutely no idea what u r talking about ???
Reply

Antaro
05-16-2005, 09:41 PM
[B] praise be to Allah and the prophet Mohammed. continue to send more chemistry questions if you can. :) :thumbs_up :applaud:
Reply

Ibn Syed
05-17-2005, 01:52 AM
Oh no, not more! :) :) :) :)
:w:
Reply

Ra`eesah
05-17-2005, 02:17 AM
Assalamu"Alaykum

Originally Posted by Danish
:sl:
sorry,but have absolutely no idea what u r talking about ???

ok Bismillaah...

Molar concentration of acid was given - it was 0.1M

Such an acid should be able to neutralize some amount of hydrogen carbonate - but it neutralizes more. So it must have more than one proton reacting.
Reply

Ra`eesah
05-17-2005, 09:07 AM
Originally Posted by ahmed687
did you know you sounded just like a College proffesor ???? (no sarcasm) :)lol

Assalamu'Alaykum,

Subhanallah, but did u understand what i posted?
Reply

Ameeratul Layl
07-23-2006, 08:59 PM
Salam,

I will be doing A2 when college begins again.

If anyone needs AS help, you are more than welcome to ask.:)

Wasalam
Reply

Ameeratul Layl
08-15-2006, 02:15 PM
Salam,

Could anyone explain homolytic fission and the star theory.
I have forgotten it. I have read through my textbook but there is too much.

Wasalam
Reply

ameen
08-15-2006, 04:48 PM
salam,

According to my Nuffield Chem. book, summarised in two sentences:

Homolytic fission is when UV (Ultraviolet) light is used / absorbed by a molecule such as chlorine (Cl-Cl ), to 'split' it into two atoms (Cl and Cl), each with an odd number of electrons on the outer shell.

This is different to the formation of ions following the gain and loss of electron/s by each atom, because in this case, a covalent bond is broken, with each atom in the bond taking one electron, to form two 'free-radicals'.

Please ask if I can clarify further.

Also, when you say 'star theory', are you talking about the life cycle of stars?

If so, is that not covered in the Biology syllabus (not Chemistry) ?

&#160;
Reply

Ameeratul Layl
08-15-2006, 04:55 PM
Originally Posted by Ameen-
salam,

Please ask if I can clarify further.

In that case, could you add diagrams to your theory. I understand diagrams better than the theory.

Also, when you say 'star theory', are you talking about the life cycle of stars? :S
Correct

If so, is that not covered in the Biology syllabus (not Chemistry) ?I have not yet come across it in the Biology book but it is in the chemistry book

*
JazakAllah for your help so far.

:w:
Reply

ameen
08-15-2006, 05:21 PM
salam,

well, this is basically what happens when a chlorine molecule absorbs UV light:

Attachment 2076

do you see how the covalent bond in the middle (left-hand side) is broken and the molecule is split into two identical free-radicals (right-hand side) ?

It's called 'homolytic fission' because 'homo-' is from the Ancient Greek meaning 'same' and 'fission' because the molecule splits.

wsalam
Reply

Arwa
08-15-2006, 05:26 PM
wa alaikum assalam

Also, when you say 'star theory', are you talking about the life cycle of stars?

If so, is that not covered in the Biology syllabus (not Chemistry) ?
Isn't it physics? ^o)
Reply

ameen
08-15-2006, 05:27 PM
salam,

yes, I was wrong. According to my book, it's Physics, under the topic - 'Forces', but it's probably Chemistry as well, since it's in sr. ameeratul layl's chemistry-book.

&#160;
Reply

ameen
08-15-2006, 06:53 PM
salam,

the following short summary of the life-cycle of a star is from a GCSE book, but still may have relevance to A-level:

&#160;
Reply

Ameeratul Layl
08-16-2006, 11:45 AM
Salam,

SubhanAllah, that is great Br. Ameen. (I take you are a brother, for some reason). It is so consice and to the point. Just what I need.
Sister Arwa, the star life cycle has not been mentioned in my AS Physics lessons. But, it sure has been mentioned in Chemistry. Do you study Physics?

Wasalam
Reply

ameen
08-17-2006, 02:18 AM
Originally Posted by Ameeratul Layl
Salam,

SubhanAllah, that is great Br. Ameen. (I take you are a brother, for some reason).

salam,

that is correct, and you are very welcome : )
Reply

Arwa
08-17-2006, 01:45 PM
Originally Posted by Ameeratul Layl
Salam,

Sister Arwa, the star life cycle has not been mentioned in my AS Physics lessons. But, it sure has been mentioned in Chemistry. Do you study Physics?

Wasalam
wa alaikum assalam

Lol nopes. I remember doing the star cycle in physics for GCSE. :thankyou:
Reply

Ameeratul Layl
08-17-2006, 01:52 PM
Originally Posted by Arwa
wa alaikum assalam

Lol nopes. I remember doing the star cycle in physics for GCSE. :thankyou:

:sl:

GCSE Physics? Hah, all I remember was the symbol for a light bulb in a circuit.

:w:
Reply

ameen
08-17-2006, 05:21 PM
as-salamu'alaikum,

to all students of A-Level Chemistry: if you are able to purchase only ONE book for your course (other than a syllabus-specific book), then I think the 'Complete A-Z Chemistry - Handbook' would be best, because it is like a 'dictionary' of all A-level Chemistry terms and concepts.

So for example, to look up 'homolytic fission', you would simply skip to the letter 'H' category in the book, and look up the 'definition' / explanation:

The book can be purchased at the following link:

http://www.amazon.co.uk/gp/product/0...725321-1523844

wsalam

&#160;
Reply

Skillganon
08-24-2006, 10:42 PM
Originally Posted by Danish
:sl:
I created this specially for us Chemistry ppl. Anyway, i follow OCR, and any1 has practical exam coming up soon?

Well,this thread is just for discussion of chemistry. Help with chem, etc

I have a go, any1 know this:

A titration was carried out using an 0.10 moldm-3 solution of an unknown acid, HxA to determine the value of ‘x’ in the acid formula. 25 cm3 of 0.15 moldm-3 sodium hydrogen carbonate solution was found to require an average titre of 12.35 cm3 of acid to just neutralise it. What is the value of x?

Well, the answer is this:
1. Amount of sodium hydrogen carbonate = 3.75 x 10-3 mol,
ratio is 1:1, so amount H+ = 3.75 x 10-3 mol
H+ is 0.3 moldm-3, so x=3

any idea how they got that? :zip:
Concentration = mole /Volume

HxA
Conc = 0.10 mol dm-3

NaOH
Conc = 0.15mol dm3
Volume = 25ml =0.025 L

H+ (Acid)
Conc= ?
Volume= 12.35ml = 0.01235

No of moles H+ = 0.025 x 0.15 = 3.75 x 10-3 moles

Conc of H+ = 3.75 x 10-3 / 0.01235 = 0.30 mol dm-3

HxA concentration is 0.1 mol dm-3 but the acid in the titration gives concentration of 0.3 mo dm3 which is 3 times stronger. x Must be 3.

Hope that helps to clarify it further.
Reply

Jayda
08-26-2006, 06:09 PM
Hola compa&#241;eros... I can help if anybody has any biochemistry questions...
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