CHEM AND BIO HELP AND TIPS HERE

[ambitious94]

each full outer shell has 8 electrons .. and.. if it was in group one, Li has 3 electrons, plus 8, you get 11. and you add another 8 electrons, you get 19. there's always 1 electron left on the outermost shell. (which shows that they're in the same group) so your answer must be A or B..

then, they 'can' be unreactive as well , cuz for noble gases, Neon has 10 electrons. Plus 8, you get 18 (Ar). plus another 8, 36 (Kr). and there's always gonna be a full outermost shell... (which shows that they're unreactive), so... yeah both students can be right, & its tick for student 1 & 2 so its A.

Thanks. But I still don't get it. I mean, it could be ANY two elements :S, how can we predict they're unreactive Any ideas anyone? Nov 2009. Q4

[Ivo]

ummmmm.. :/ lol how are we supposed to solve that question? :p

LOLS!  Which paper and year was it?

[The Golden Girl =D]

this drove me crazy during my IGCSEs too..

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.

i read it like 4 times lol  thx mate

[The Golden Girl =D]

By the way another Q (defenityl getin my butt kicked today  )

same year Q 18 

[Shazizzzle]

No comment on today's paper. :/

[Vin]

ummmmm.. :/ lol how are we supposed to solve that question? :p

study .. dont waste your time

[holtadit]

No comment on today's paper. :/

Keep it that way for 24 Hours

[thenewkid™]

2days ppr ws more like Environmental management than bio

[Vin]

By the way another Q (defenityl getin my butt kicked today  )

same year Q 18 

this is test for zinc anion .. SOLUBLE in excess for both is the ans A ??

[The Golden Girl =D]

this is test for zinc anion .. SOLUBLE in excess for both is the ans A ??

ya it is and i don't get it

[holtadit]

THIS IS A GENERAL NOTICE TO ALL USERS:


PLEASE REFRAIN FROM DISCUSSING EXAM DETAILS UNTIL 24 HOURS HAVE PASSED

[Lariemeeva]

I hope someone can still answer my doubt.

Can anyone list down all the colours of Metals, non-metals, gases and everything else that's included in the syllabus for Paper 1? (Including Hydroxide, etc..) There are a lot of questions about it especially in electrolysis. Plus the oxides of metals

[Baladya]

THIS IS A GENERAL NOTICE TO ALL USERS:


PLEASE REFRAIN FROM DISCUSSING EXAM DETAILS UNTIL 24 HOURS HAVE PASSED

yo ari u saw my message?

By the way guys: When is hydrogen produced from cracking?

[jellybeans]

study .. dont waste your time

hahaha, i've.. already studied but.. OKAY, lol i'm still gona do more pastyears first... :B

[Vin]

ya it is and i don't get it

You might have .. u should have done this for paper 6