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Author Topic: Edexcel CHEMISTRY DOUBTS!!!!  (Read 269221 times)

Offline Mike Benn

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1020 on: May 08, 2011, 07:37:48 pm »
Quote from: SkyPilotage on May 08, 2011, 07:30:31 pm
due to the electrons moving around in 3-dimensions..it induces charges on other particles or molecules but its very weak compared to permanent dipoles..

Thank you very much
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Offline ~ Miss Relina ~

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1021 on: May 09, 2011, 04:45:18 pm »
in both attachrmnt plz notice Q 6b in JAn 2009 and Q 5 in JAn 2010 and tell me diiference why in 2009 it was mean bond enthalpy and why in 2010 it was equation A
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Amelia

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1022 on: May 09, 2011, 05:11:53 pm »
Quote from: Relina on May 09, 2011, 04:45:18 pm
in both attachrmnt plz notice Q 6b in JAn 2009 and Q 5 in JAn 2010 and tell me diiference why in 2009 it was mean bond enthalpy and why in 2010 it was equation A

In ppr. 2010, Q5 - the question is to find bond enthalphy for C-H (one carbon bonded with one hydrogen).
In ppr. 2009, Q6 - it states the mean bond enthalphy for CH4, (Carbon bonded with four hydrogens)


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Offline ~ Miss Relina ~

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1023 on: May 09, 2011, 05:15:27 pm »
Quote from: Amelia on May 09, 2011, 05:11:53 pm
In ppr. 2010, Q5 - the question is to find bond enthalphy for C-H (one carbon bonded with one hydrogen).
In ppr. 2009, Q6 - it states the mean bond enthalphy for CH4, (Carbon bonded with four hydrogens)



but in Q5 it said mean bond enthalpy so should  it be just one bond and why it is not C
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Amelia

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1024 on: May 09, 2011, 05:25:39 pm »
Quote from: Relina on May 09, 2011, 05:15:27 pm
but in Q5 it said mean bond enthalpy so should  it be just one bond and why it is not C

It said only C-H bond. It would have been 'C' if the question said - find mean bond enthalphy for 'CH4' molecule.
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Offline ~ Miss Relina ~

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1025 on: May 09, 2011, 11:00:44 pm »
Quote from: Amelia on May 09, 2011, 05:25:39 pm
It said only C-H bond. It would have been 'C' if the question said - find mean bond enthalphy for 'CH4' molecule.
Thanks plz here Q 10
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Offline Amii

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1026 on: May 10, 2011, 12:07:00 am »
Quote from: Relina on May 09, 2011, 11:00:44 pm
Thanks plz here Q 10
-First convert the volume from cm3 to dm3.
-Then find the number of moles.
-Then multiply the number of moles with Avagadro constant
-Then multiply the answer with the total number of ions present

a) 10 cm3 = 0.01 dm3

No. of moles = C X V = 0.1 X 0.01 = 0.001 moles

=0.001 X 6.022 x10^23
=6.022X10^20

6.022X10^20  X 2 (Total number of ions present)
=1.204X10^21

b) 20 cm3 = 0.02 dm3

No. of moles = C X V = 0.05 X 0.02 = 0.001 moles

=0.001 X 6.022 x10^23
=6.022X10^20

6.022X10^20  X 2 (Total number of ions present)
=1.204X10^21

c) 20cm3= 0.02 dm3

No. of moles = C X V = 0.05 X 0.02 = 0.001 moles

=0.001 X 6.022 x10^23
=6.022X10^20

6.022X10^20  X 3 (Total number of ions present)
=1.8066 X10^21

d) 13.33 cm3 = 0.01333 moles

No. of moles = C X V = 0.05 X 0.01333 = 6.665X10^-4 moles

= 6.665X10^-4 X 6.022 X10^23
=4.013663 x 10^ 20

4.013663 x 10^ 20 x 3(Total number of ions present)
=1.204 X 10^21

Take care  :D
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Offline ~ Miss Relina ~

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1027 on: May 10, 2011, 08:33:14 am »
Quote from: Amii on May 10, 2011, 12:07:00 am
-First convert the volume from cm3 to dm3.
-Then find the number of moles.
-Then multiply the number of moles with Avagadro constant
-Then multiply the answer with the total number of ions present

a) 10 cm3 = 0.01 dm3

No. of moles = C X V = 0.1 X 0.01 = 0.001 moles

=0.001 X 6.022 x10^23
=6.022X10^20

6.022X10^20  X 2 (Total number of ions present)
=1.204X10^21

b) 20 cm3 = 0.02 dm3

No. of moles = C X V = 0.05 X 0.02 = 0.001 moles

=0.001 X 6.022 x10^23
=6.022X10^20

6.022X10^20  X 2 (Total number of ions present)
=1.204X10^21

c) 20cm3= 0.02 dm3

No. of moles = C X V = 0.05 X 0.02 = 0.001 moles

=0.001 X 6.022 x10^23
=6.022X10^20

6.022X10^20  X 3 (Total number of ions present)
=1.8066 X10^21

d) 13.33 cm3 = 0.01333 moles

No. of moles = C X V = 0.05 X 0.01333 = 6.665X10^-4 moles

= 6.665X10^-4 X 6.022 X10^23
=4.013663 x 10^ 20

4.013663 x 10^ 20 x 3(Total number of ions present)
=1.204 X 10^21

Take care  :D
that is what i misse up  :o
Thanks alot  :)
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Offline red_911

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1028 on: May 10, 2011, 02:56:00 pm »
what are the general reasons in chemistry paper 3b of why the reation does not produce a 100% yield ?
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Offline Assi1993

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1029 on: May 10, 2011, 09:11:06 pm »
guys..ws thre chem u 5 n 6 exam on jan 10??
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Offline The Golden Girl =D

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1030 on: May 11, 2011, 06:57:13 am »
Quote from: red_911 on May 10, 2011, 02:56:00 pm
what are the general reasons in chemistry paper 3b of why the reation does not produce a 100% yield ?

I guess these are the general ones;

loss in transfer.
Some remained in the beaker/flask/funnel.
in case they're organic reagents then it's because they're volatile.
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**RoRo**

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1031 on: May 11, 2011, 08:52:41 am »
What's the name of this compound, CH3CH2CH2OCH2NH2?
Is it methoxypropaneamine OR Aminomethoxypropane?
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Offline Master_Key

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1032 on: May 11, 2011, 08:54:21 am »
Quote from: The Secret on May 11, 2011, 08:52:41 am
What's the name of this compound, CH3CH2CH2OCH2NH2?
Is it methoxypropaneamine OR Aminomethoxypropane?
Name of functional group is placed last.

Like propanenitrile.
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Offline EMO123

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1033 on: May 11, 2011, 08:59:39 am »
Quote from: The Secret on May 11, 2011, 08:52:41 am
What's the name of this compound, CH3CH2CH2OCH2NH2?
Is it methoxypropaneamine OR Aminomethoxypropane?
i think it is Methoxypopaneamine  :-\
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**RoRo**

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #1034 on: May 11, 2011, 09:18:09 am »
Quote from: EMO123 on May 11, 2011, 08:59:39 am
i think it is Methoxypopaneamine  :-\

OR Methoxyaminopropane?
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