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Author Topic: Edexcel CHEMISTRY DOUBTS!!!!  (Read 253739 times)

Offline ~ Miss Relina ~

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #810 on: March 23, 2011, 11:38:17 am »
I have another question about choosing the titres to get the mean titre  what do u depend on to choose  this is in tittrations  ???
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Offline The Golden Girl =D

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #811 on: March 23, 2011, 11:40:19 am »
they have to be within 0.2 cm3 from each other/concordant.
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Offline ~ Miss Relina ~

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #812 on: March 23, 2011, 10:46:27 pm »
Thanks
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Offline Blizz_rb93

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #813 on: March 24, 2011, 10:08:54 am »
this is from the chemistry as revision guide, its one of the thinking task
it says

Will the reactions of 24Mg and 23Mg with oxygen be any different? If so, how? If not, why?

Thank you :)
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Offline Amii

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #814 on: March 24, 2011, 06:14:33 pm »
Quote from: Blizz_rb93 on March 24, 2011, 10:08:54 am
this is from the chemistry as revision guide, its one of the thinking task
it says

Will the reactions of 24Mg and 23Mg with oxygen be any different? If so, how? If not, why?

Thank you :)

They are isotopes - with different number of neutrons but same number of electrons and protons . Same electronic configuration means identical chemical reactions.

Not sure though  :-\
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Offline Amii

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #815 on: March 25, 2011, 12:52:23 pm »
The ratio of H2S and H20 is 1:1, so 500cm3 of hyrogen sulfide will produce 500cm3 of steam.

Volume of gas = moles X molar volume
Units of both the volumes should be the same,both must be either dm3 or cm3.

Molar volume = 24 dm3 mol-1  = 24 000 cm3 dm -1 

Number of moles of Hydrogen Sulfie = 500/24000 = 0.02083 moles

H2S    :   H20
2        :   2 
0.0208 :  x

x= 0.208 moles of H20

Volume of H20 = 0.0208X 24000= 500 cm3

If you want do the calculations in dm3 then convert the the volumes which are in cm3 to dm3 by dividing it by 1000(1dm3=1000cm3) and take the molar volume as 24 dm3 mol-1.

Take care :D

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Offline Amii

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #816 on: March 25, 2011, 01:17:08 pm »
Where did the question go?  ::)
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Offline Blizz_rb93

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #817 on: March 25, 2011, 01:22:36 pm »
Quote from: Amii on March 25, 2011, 01:17:08 pm
Where did the question go?  ::)
I removed it before you posted the question cause I wanted to ask another question but still thank you for your answer!! I didn't notice you were posting the answer so when I figured it out on my own I removed it thats why.
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Offline Amii

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #818 on: March 25, 2011, 01:33:32 pm »
Quote from: Blizz_rb93 on March 25, 2011, 01:22:36 pm
I removed it before you posted the question cause I wanted to ask another question but still thank you for your answer!! I didn't notice you were posting the answer so when I figured it out on my own I removed it thats why.
Oh okay.No problem  :D
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Offline ~ Miss Relina ~

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #819 on: March 25, 2011, 01:42:06 pm »
does HCl contain permanent dipole-dipole between its molecules  ???
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Offline Amii

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #820 on: March 25, 2011, 02:03:52 pm »
Quote from: Relina on March 25, 2011, 01:42:06 pm
does HCl contain permanent dipole-dipole between its molecules  ???
Yes.HCl is a polar molecule,hence it will have permanent dipole-dipole as well as instantaneous induced dipole-induced dipole intermolecular forces between its molecules.

http://www.chemguide.co.uk/atoms/bonding/vdw.html This might help :)

Take care  :D
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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #821 on: March 25, 2011, 02:28:09 pm »
Quote from: Relina on March 25, 2011, 01:42:06 pm
does HCl contain permanent dipole-dipole between its molecules  ???

Although it has permanent dipole-dipole forces between molecules the DOMINANT intermolecular force is Hydrogen bonding.
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Offline Amii

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #822 on: March 25, 2011, 03:29:26 pm »
Quote from: Ari Ben Canaan on March 25, 2011, 02:28:09 pm
Although it has permanent dipole-dipole forces between molecules the DOMINANT intermolecular force is Hydrogen bonding.
There can not be hydrogen bonding between HCl molecules.Hydrogen bonding can only occur between an electropositive hydrogen atom and an electronegative oxygen,nitrogen or fluorine atom.

Chlorine atoms are too large to form hydrogen bonds.

« Last Edit: March 25, 2011, 03:30:57 pm by Amii »
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Offline The Golden Girl =D

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #823 on: March 25, 2011, 03:32:19 pm »
^ True ..between H -F and H - N  and O -H  ;)
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Offline Blizz_rb93

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Re: Edexcel CHEMISTRY DOUBTS!!!!
« Reply #824 on: March 25, 2011, 06:47:22 pm »
A student prepared a sample of the fertilizer ammonium sulfate by adding ammonia solution to sulfuric acid:

2NH3 (aq) + H2SO4 (aq) --> (NH4)SO4 (aq)

Calculate the theoretical maximum yield that can be obtained by reacting 25.0 cm3 of 2.0mol dm-3 ammonia solution with an excess of sulfuric acid

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