ALL CIE CHEMISTRY DOUBTS HERE !!

[$H00t!N& $t@r]

Can you please post the paper?

Here it is: http://www.xtremepapers.me/CIE/International%20A%20And%20AS%20Level/9701%20-%20Chemistry/9701_w10_qp_23.pdf

[Vin]

2 H₂S + 3O₂  -> 2SO₂ + 2H₂O

Let oxi. no. of S be x

H2S => +2 + x = 0
sum of all oxidation states of atoms  0
so x = -2

SO2 => x + 2(-2)
x = +4

S => for any atom its 0

SO2 is reduced from +4 to 0

^This is what I did when i first saw the ques. After checking the ms I read the question again, however it clearly says "the oxidation numbers of each of the sulfur-containing substances in this reaction? "
which should be 0
and not oxi. no. of Sulfur in these compounds :/ If you get what I mean.

Sorry to complicate things all over again, I'm confused myself. Lets wait for someone smarter to conform

[$H00t!N& $t@r]

2 H₂S + 3O₂  -> 2SO₂ + 2H₂O

Let oxi. no. of S be x

H2S => +2 + x = 0
sum of all oxidation states of atoms  0
so x = -2

SO2 => x + 2(-2)
x = +4

S => for any atom its 0

SO2 is reduced from +4 to 0

^This is what I did when i first saw the ques. After checking the ms I read the question again, however it clearly says "the oxidation numbers of each of the sulfur-containing substances in this reaction? "
which should be 0
and not oxi. no. of Sulfur in these compounds :/ If you get what I mean.

Sorry to complicate things all over again, I'm confused myself. Lets wait for someone smarter to conform

I understand what you mean... they want us to find out the oxidation number for the element attached to sulphur and not sulphur itself, but I thought that the oxidation number for S is -2 cuz it's right below oxygen..  and for the second one, SO2, why did you find the oxidation number for sulphur and not oxygen, the way you did for the first one, H2S... the last one was pretty simple

[Sue T]

i have a ques from paper 41 mj 10
3(c) The molecule dichlorocarbene, CCl2, can be produced under certain conditions. It is
highly unstable, reacting with water to produce carbon monoxide and a strongly acidic
solution.
(i) Suggest the electron arrangement in CCl2 and draw a dot-and-cross diagram
showing this. Predict the shape of the molecule.

th answer was
    ..            ..
Cl:C:Cl or Cl=C–Cl
+  –
bent or non-linear or angle = 100–140o

how do we arrive at this structure?

[Amelia]

i have a ques from paper 41 mj 10
3(c) The molecule dichlorocarbene, CCl2, can be produced under certain conditions. It is
highly unstable, reacting with water to produce carbon monoxide and a strongly acidic
solution.
(i) Suggest the electron arrangement in CCl2 and draw a dot-and-cross diagram
showing this. Predict the shape of the molecule.

th answer was
    ..            ..
Cl:C:Cl or Cl=C–Cl
+  –
bent or non-linear or angle = 100–140o

how do we arrive at this structure?

One lone pair, two bond pairs. Repulsion between lone pairs and bond pairs.

http://upload.wikimedia.org/wikipedia/commons/8/8c/Dichlorocarbene-from-MW-2001-2D.png

[Vin]

I understand what you mean... they want us to find out the oxidation number for the element attached to sulphur and not sulphur itself, but I thought that the oxidation number for S is -2 cuz it's right below oxygen..  and for the second one, SO2, why did you find the oxidation number for sulphur and not oxygen, the way you did for the first one, H2S... the last one was pretty simple

Okay, S₈ is the molecule for sulfur, and is written as S in chemical eqaution, in the atomic form right? Hence, S is 0.

Ok, we know the oxidation state of oxygen, O,  which is -2.
So, S + O2 = 0
x + 2 (-2) = 0
x = -4

Cuz to find the oxidation no. for any atom X in a compound you're supposed to know the other as well.

[iluvme]

November 2006,

Q4 f and g
Q5 f ii)

Thank You

[EMO123]

November 2006,

Q4 f and g
Q5 f ii)

Thank You

i am sory but can you tell us which paper

[iluvme]

i am sory but can you tell us which paper

Oh sorry Paper 2

[SkyPilotage]

November 2006,

Q4 f and g
Q5 f ii)

Thank You

Q4 f) First of all cracking alkanes forms alkanes or alkenes, since Z is unsaturated then its an alkene CnH2n.
You found the molecular mass in ii) as 42 g so you can do it by trial and error or : 12n+(1)x(2n)=42 ---> 14n=42 ---> n=3 so its C3H6 (propene)
     g) whenever u show the monomer or a polymer, the molecule should be shown in the form of "ethene" so just show 2 molecules of propene (without double bond ofcourse) as the polymer....

Q5 f)ii)  solubility of water relates to hydrogen bonds... So the product must have formed hydrogen bonds with water...(usully from the hydroxyl group OH-)

[iluvme]

Q4 f) First of all cracking alkanes forms alkanes or alkenes, since Z is unsaturated then its an alkene CnH2n.
You found the molecular mass in ii) as 42 g so you can do it by trial and error or : 12n+(1)x(2n)=42 ---> 14n=42 ---> n=3 so its C3H6 (propene)
     g) whenever u show the monomer or a polymer, the molecule should be shown in the form of "ethene" so just show 2 molecules of propene (without double bond ofcourse) as the polymer....

Q5 f)ii)  solubility of water relates to hydrogen bonds... So the product must have formed hydrogen bonds with water...(usully from the hydroxyl group OH-)

Q5 It doesn't have to do anything with water being polar? 

[SkyPilotage]

Q5 It doesn't have to do anything with water being polar? 

Hydrogen bonds are types of permanent dipole-dipole forces which exists only if the molecule is polar!!!!! But a polar molecule may have Permanent dipole forces but no hydrogen bonds...So u must mention tht hydrogen bonds form!

[iluvme]

+ Rep Thank You!!

Besides I've got more doubts,   

November 2007 Paper 2
Q1 b, Q2 e, Q3 d, Q5 e and d

[EMO123]

1 b)
covalent bond is due to the attraction between the nuclei and electrons and there is an attraction electrostatic forces

[EMO123]

2 e)i)

460K is Al₂Cl₆
1150K is AlCl₃

2 e)ii)
in the attachment

2 e)iii)
in the attachment