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Author Topic: Edexcel CHEMISTRY DOUBTS!!!!  (Read 253889 times)

elemis

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #960 on: May 02, 2011, 08:45:20 am »
Quote from: Nidzzz on May 02, 2011, 01:03:54 am
Can Some one help me wid  2009 Unit 1 21 C (iv)   

Could you post a link ?
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Offline NidZ- Hero

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #961 on: May 02, 2011, 11:02:29 am »
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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #962 on: May 02, 2011, 11:15:18 am »
How does the existence of ring structure give rise to cis  and trans isomers
and do we have these kind of isomers to name
« Last Edit: May 02, 2011, 11:41:03 am by Nidzzz »
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elemis

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #963 on: May 02, 2011, 11:45:29 am »
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elemis

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #964 on: May 02, 2011, 11:51:52 am »
Firstly, you have to understand we are basically reacting an alkene with Hydrogen to produce a product that has NO double bonds.

Thus, the hydrogen will add across each double bond.

Construct an equation :

C10H16 + H2 ------> X                       

NOTE : X is the product that we are trying to determine the structural formula of.

1.36 grams of the Mycrene reacted.  1.36/136 = 0.01 moles

0.72 dm3 of Hydrogen reacted.          0.72/24 = 0.03 moles

Notice that the ration of Mycrene to Hydrogen is    1:3

Therefore for every one mole of Mycrene 3 moles of hydrogen MOLECULES are required.

Balancing the equation :

C10H16 + 3H2 ------> X     

Now you have proven that 6 hydrogen ATOMS are added just draw the formula !
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Offline Darkstar3000

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #965 on: May 02, 2011, 11:54:49 am »
This question concerns the titration of a solution of sodium hydroxide with a solution of hydrochloric acid. As the titration proceeds pH of the mixture changes

a) What was the pH when 24.95 cm^3 of 1.00 mol dm^-3 NaOh (aq) had been added to 25 cm^3 of 1.00 mol dm^-3 HCL(aq) ? ANS  : 3

How do I calculate this ? I tried calculation and what I did was -log 2 and subtracted the answer from 14 but it makes no difference. Can you please explain this with as much detail as possible because I'm a bit shakey on this

Thank you
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Offline NidZ- Hero

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #966 on: May 02, 2011, 12:26:08 pm »
Quote from: Ari Ben Canaan on May 02, 2011, 11:51:52 am
Firstly, you have to understand we are basically reacting an alkene with Hydrogen to produce a product that has NO double bonds.

Thus, the hydrogen will add across each double bond.

Construct an equation :

C10H16 + H2 ------> X                       

NOTE : X is the product that we are trying to determine the structural formula of.

1.36 grams of the Mycrene reacted.  1.36/136 = 0.01 moles

0.72 dm3 of Hydrogen reacted.          0.72/24 = 0.03 moles

Notice that the ration of Mycrene to Hydrogen is    1:3

Therefore for every one mole of Mycrene 3 moles of hydrogen MOLECULES are required.

Balancing the equation :

C10H16 + 3H2 ------> X     

Now you have proven that 6 hydrogen ATOMS are added just draw the formula !
Thanks alot buddy but i was askin How to draw its kinda a different
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elemis

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #967 on: May 02, 2011, 02:54:16 pm »
Quote from: Nidzzz on May 02, 2011, 12:26:08 pm
Thanks alot buddy but i was askin How to draw its kinda a different


Just add hydrogens across each double bond.... what's so difficult ?
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Offline ~ Miss Relina ~

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #968 on: May 02, 2011, 03:19:14 pm »
Quote from: Nidzzz on May 02, 2011, 12:26:08 pm
Thanks alot buddy but i was askin How to draw its kinda a different

here
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Offline ~ Miss Relina ~

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #969 on: May 02, 2011, 09:30:19 pm »
well 1.what is the benedict's solution used for ???
      2.how to prepare a saturated solution accurately ???
      3.explain the mean bond enthalpy and distinguissh between ti and the bond enthalpy ???
Thanks in advance
« Last Edit: May 02, 2011, 09:32:03 pm by Relina »
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Offline Vampire-Love4ever

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #970 on: May 02, 2011, 11:34:43 pm »
Please explain this question!
The answer which I wrote is from the marking scheme and its for two marks but only 1 point is given-which I dont understand. :/

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #971 on: May 02, 2011, 11:38:52 pm »
plz help with (ii) part!
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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #972 on: May 02, 2011, 11:49:11 pm »
the image attached is used to reflux organic compound and we must find two mistakes in the diagram.
In the marking scheme, they havent mentioned anything about the flask being sealed which will lead to pressure build up.
So, if I mention this point in the exam- will it be wrong?

This from June 2011 Unit6b Q4biii
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Offline NidZ- Hero

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #973 on: May 03, 2011, 05:03:54 am »
Quote from: Vampire-Love4ever on May 02, 2011, 11:49:11 pm
the image attached is used to reflux organic compound and we must find two mistakes in the diagram.
In the marking scheme, they havent mentioned anything about the flask being sealed which will lead to pressure build up.
So, if I mention this point in the exam- will it be wrong?

This from June 2011 Unit6b Q4biii
Alrite i just Know that  water inlet arrangement  is wrong water enter from down and leave from top of condenser
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Offline NidZ- Hero

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #974 on: May 03, 2011, 06:12:57 am »
write the formula of compound iron(iii) nitrate(v) ?
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