CHEM AND BIO HELP AND TIPS HERE

[Shazizzzle]

Oxidation States of Elements is always 0. Its a rule.

Thanks a million!

[Ivo]

The equation shows the reaction between a halogen and the aqueous ions of another halogen.
X2 + 2Y- ? 2X- + Y2
What could X2 and the colour of Y– be?

A chlorine, brown
B chlorine, colourless
C iodine, brown
D iodine, colourless

Answer is B..... HOWWWWWWWWWWWWWW? Plzz help me out someone!

has to be chlorine, as it is more reactive than iodine.  halide ions are always colourless

[The Golden Girl =D]

plz explain Q20 year november 2007  

thx in advance

[Ghost Of Highbury]

Thanks a million!

no problem, check the post again..check the link

[Ivo]

S + 02 --> S02

S - oxidation number 0..
O2 - oxidation number 0

SO2 --> oxidation number of O = (-2*2) = -4 , thus oxidation number of S = +4

S--> 0 to 4 oxidation
O -> 0 to -4 reduction

thus redox.

2S02 + 02-->2 S03

2SO2 -> oxidation number of O = (-2*2) = -4, thus S = +4.  O2 -> 0, final of O = -4+0 = -4

SO3--> Oxidation number of O = (-2*3) = -6, of S = +6

Final , S --> 4 to 6 oxidation

         O --> -4 to -6 reduction

SO3 + H20--> H2SO4

SO3 --> O = (-3*2) = -6 , thus S = +6

H2O --> O = -2, thus H = +2

O in both compounds thus, final number of O = -6-2 = -8

H2SO4--> O = (-2*4) = -8, thus H = +2, as final oxidation number of the compound shud be 0, -8+2+S = 0

thus, S = +6

now the changes

S --> 6 to 6
H --> 2 to 2
O --> -8 to -8..

NOt redox.

why is oxidation number 4 in first one, sone pls explain

[Ivo]

plz explain Q20 year november 2007  

thx in advance

carbon reacts with air to form carbon dioxide, released, so mass of carbon decreases.

copper reacts wtih oxygen to form copper oxide, which is soluble, so gets accumulated.

so answer is b

[ambitious94]

has to be chlorine, as it is more reactive than iodine.  halide ions are always colourless

O_O....I think I need another pair of glasses XD...
Thanks a lot. Really nice of all of you to help out like this!

[Ghost Of Highbury]

eee the OVERALL oxidation state of a COMPOUND is 0. that doesnt mean the elements IN the compound also have 0 as the oxidation number...

for SO2...

Oxygen has a fixed oxidation number, but not sulfur, so first we determine the oxidation number of O2 = (-2*2+ = -4

now as i told previously, the OVERALL oxidation state of a COMPOUND has to be 0

so S has to be +4 to make the overall oxidation no. of SO2 = 0

this way -4+4 = 0

[The Golden Girl =D]

plz explain Q20 year november 2007 AND Q38 plz

thx in advance

i'm waitin  

[the_grim_reaper]

is the ans C ??

Yes it should be C!!!! THat's what I thought too! But that no good unofficial mark scheme claims its A (which is impossible!!! I'll chop my hands if someone proves its A).

Plus one final thing, why should aqueous copper sulphate be used in electroplating something with copper. Why not only a molten copper salt. And in M/J 2007 question 16 what is the answer??? PLZ HELP!!!

[the_grim_reaper]

Sorry don't answer mj 07. I didn't see that it had been answered

[Ivo]

Yes it should be C!!!! THat's what I thought too! But that no good unofficial mark scheme claims its A (which is impossible!!! I'll chop my hands if someone proves its A).

Plus one final thing, why should aqueous copper sulphate be used in electroplating something with copper. Why not only a molten copper salt. And in M/J 2007 question 16 what is the answer??? PLZ HELP!!!

u talking about refining copper?

[Ivo]

eee the OVERALL oxidation state of a COMPOUND is 0. that doesnt mean the elements IN the compound also have 0 as the oxidation number...

for SO2...

Oxygen has a fixed oxidation number, but not sulfur, so first we determine the oxidation number of O2 = (-2*2+ = -4

now as i told previously, the OVERALL oxidation state of a COMPOUND has to be 0

so S has to be +4 to make the overall oxidation no. of SO2 = 0

this way -4+4 = 0

So all compunds have oxidation number of 0?

Then why is it that sulphur is +4, i thought cos it's in group 6, then it is -2.

how do oxidation numbers work?

[the_grim_reaper]

u talking about refining copper?

NO! electroplating something (a key) with copper....

[Ivo]

i'm waitin  

Has been answered previously