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Author Topic: Edexcel CHEMISTRY DOUBTS!!!!  (Read 254025 times)

Offline Uchia

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #135 on: May 19, 2010, 08:00:51 pm »
sorry but which unit
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Offline Kim

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #136 on: May 19, 2010, 08:02:43 pm »
ooooh sorry unit 1
6ch01
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Offline Uchia

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #137 on: May 19, 2010, 08:04:49 pm »
if it was unit 2 then barium hydroxide cz as you go down the group they become more soluble

if it was unit 1 then D cz as you can see this question depends on the polarising power and the polarising power depends on the ionic charge and radius
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Offline Meticulous

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #138 on: May 19, 2010, 08:04:56 pm »
Quote from: kim on May 19, 2010, 07:53:15 pm
hey cud sum1 tell the answer to jan 2009 q2
and how u got it??thanks

There is a law in physics called coulombs law of electrostatic forces of attraction:

F= kQ1 Q2 / r2

Therefore, the force is affected by charge and radius. Got that?
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Offline Kim

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #139 on: May 19, 2010, 08:07:07 pm »
heey thanks both of ya
ya i got it
and also same paper q6 a and b
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Offline Saladin

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #140 on: May 19, 2010, 08:32:42 pm »
Quote from: kim on May 19, 2010, 07:53:15 pm
hey cud sum1 tell the answer to jan 2009 q2
and how u got it??thanks

In 30 minutes.
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Offline Uchia

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #141 on: May 19, 2010, 09:00:09 pm »
as you can see in part a the CH4 became CH3 which means  a C-H bond has been broken therefore it is a bond enthalpy

in part b 4 of the C-H bonds have been broken so its a mean bond enthalpy cz they are all same bonds and a mean value was taken for all of them
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Offline Kim

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #142 on: May 19, 2010, 09:11:07 pm »
Quote from: damlaj on May 19, 2010, 09:00:09 pm
as you can see in part a the CH4 became CH3 which means  a C-H bond has been broken therefore it is a bond enthalpy

in part b 4 of the C-H bonds have been broken so its a mean bond enthalpy cz they are all same bonds and a mean value was taken for all of them

thank u sooooooo much
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Offline raimunts

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #143 on: May 19, 2010, 11:59:54 pm »
What does the "Y" shaped skeletal formula represent? Can someone please provide notes or something on drawing/reading skeletal formula. I have major confusions particularly regarding the branched chain skeletal formulas. And ring/benzenes are not in Unit 1 Syllabus ryt?
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Offline wakemeup

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #144 on: May 20, 2010, 02:57:03 am »
That 'Y' would represent 2-methyl propane. Just remember, in this case each line represents a C-C bond and everything else will fall into place. And no, there are no rings/benzenes in Unit 1.
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Offline Darth Austrakast

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #145 on: May 20, 2010, 08:01:48 am »
Quote from: raimunts on May 19, 2010, 11:59:54 pm
What does the "Y" shaped skeletal formula represent? Can someone please provide notes or something on drawing/reading skeletal formula. I have major confusions particularly regarding the branched chain skeletal formulas. And ring/benzenes are not in Unit 1 Syllabus ryt?

no benzenes r not in our syllabus
here are some links http://www.chemguide.co.uk/basicorg/conventions/names.html#top
                          http://www.chemguide.co.uk/basicorg/conventions/draw.html#top

hope it helps  ;D
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Offline coatseville

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #146 on: May 20, 2010, 12:21:50 pm »
I was wondering does anyone have good notes of hess's law diagrams?
Thanks :)
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Offline Igcseboy

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #147 on: May 20, 2010, 12:42:48 pm »
Quote from: Engraved on May 19, 2010, 07:37:21 pm
For (a) 3 moles of CO2 is formed. And 2 moles of O2 was used to form water. Thus 8 hydrogens were used.
Thus, C3H8

(b) 1 gram of H2 will mean 1 mole of H2. 20 grams of Ne will mean 1 mole of Ne. Thus same number of atoms as Hydrogen.


how did u calculate the moles for a part

and for b hw is moles for H2 1... its is 1/2=0.5 moles :S:S:S
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Offline Darth Austrakast

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #148 on: May 20, 2010, 01:10:30 pm »
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Offline raimunts

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #149 on: May 20, 2010, 03:11:19 pm »
                  Mg(s) + Cu(NO3)2(aq)        Mg(NO3)2(aq) + Cu(s)
In the self-heating cans, the bottom has a compartment containing copper(II) nitrate
solution. When a button on the bottom of the can is pressed, the magnesium powder is
released into the compartment where it reacts with the copper(II) nitrate solution.
(a) A student investigated the enthalpy change for this reaction by measuring
     50.0 cm3 of 0.300 mol dm–3 copper(II) nitrate solution into a 100 cm3 beaker and
     adding 1g (an excess) of magnesium powder.
     The results are shown below.
         Temperature of copper(II) nitrate solution at start       = 22 C
         Temperature of mixture after reaction                     = 43 C

(i) Calculate the energy change which took place. The specific heat capacity of the
    solution is 4.20 J g–1K–1.
    Which is the correct value for the energy change in joules?

[6CH01, Specimen Paper]

How to solve this? Answer in mark scheme is 4410 Joules
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