POST YOUR BIO AND CHEM PAPER 1 DOUBT HERE !!!!

[NabzJ]

Anyone has the mark scheme for 1994 - 2003 chemistry ?

 

[balloonsandhighlighters]

I thought it was B... Why C? Thank youuuuu so very much!

 

[L-Girl]

View attachment 12169

I thought it was B... Why C? Thank youuuuu so very much!

in 1, sulphur is oxidised into sulphur dioxied
in 2, sulphur dioxide reacts with oxygen and so it's oxidised into sulphur trioxide
in 3, there's no oxidation nor reduction
so 1 and 2 only, which is C

 

[fishcook]

in 1, sulphur is oxidised into sulphur dioxied
in 2, sulphur dioxide reacts with oxygen and so it's oxidised into sulphur trioxide
in 3, there's no oxidation nor reduction
so 1 and 2 only, which is C

but isnt redox reaction for reduction followed by oxidation in terms of electron transfer?

 

[L-Girl]

but isnt redox reaction for reduction followed by oxidation in terms of electron transfer?

what do u mean?

 

[balloonsandhighlighters]

in 1, sulphur is oxidised into sulphur dioxied
in 2, sulphur dioxide reacts with oxygen and so it's oxidised into sulphur trioxide
in 3, there's no oxidation nor reduction
so 1 and 2 only, which is C

but i thought a redox reaction was one that had reduction and oxidation... so one thing gets reduced, the other oxidised. 1 and 2 had only one , which is oxidation... am i wrong or right? thanks !

 

[Evangeline]

umm it's good am like just doing 3-4 papers per day.
Hows ur prep?

me too solving half chem and half bio... best of luck sis

 

[L-Girl]

but i thought a redox reaction was one that had reduction and oxidation... so one thing gets reduced, the other oxidised. 1 and 2 had only one , which is oxidation... am i wrong or right? thanks !

ummmm i guess you're right but reaction 3 doesn't involve oxidation or reduction :/
and in 1 Oxygen is reduced as it gains 2 electrons and it is also reduced in 3

 

[fishcook]

what do u mean?

like.. in a reaaction there has to gain and loss of electron for it to be called a redox reaction.

 

[Evangeline]

here are some bio notes for guidance .. hope it helps
http://www.scribd.com/sbakrey/d/54336596-IGCSE-Biology-Notes
please pray for me

 

[areebaization]

me too solving half chem and half bio... best of luck sis

best of luk 2 u too

 

[Evangeline]

best of luk 2 u too

if you have any problems considering bio this link is very helpful http://www.scribd.com/sbakrey/d/54336596-IGCSE-Biology-Notes

 

[Evangeline]

this is a very useful chem link
http://www.scribd.com/doc/53176063/Chemistry-IGCSE-revision-updated-2011
good luck

 

[balloonsandhighlighters]

ummmm i guess you're right but reaction 3 doesn't involve oxidation or reduction :/
and in 1 Oxygen is reduced as it gains 2 electrons and it is also reduced in 3

but oxidation is also the gain of oxygen, and as you can see, SO3 became SO4...? So it gained...?

 

[Skynox]

In equation 1 : Sulfur is oxidized since it gained oxygen..Oxygen molecules are reduced into atoms.
In equation 2 : Same as the previous one
In equation 3 :Sulfur trioxide is oxidized but the oxidation state of oxygen remained constant.
So equation 1,2 there was an oxidation and reduction due to the change in the Oxidation state of oxygen molecule
In equation 3, only oxidation took place
SO3 oxidized and H2o remained..
That way we could consider any gain of oxygen as a redox reaction not just oxidation when speaking about atoms reacted with molecules..

Check this
^^

 

[L-Girl]

can someone please explain question 27, november 2010 bio?

 

[L-Girl]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_w10_qp_11.pdf

 

[Razo513]

Anyone has the mark scheme for 1994 - 2003 chemistry ?

 

[Razo513]

can someone please explain question 27, november 2010 bio?

to answer ur question ... look at the calender ovulation doesnt occur until sept 15 .. the max days a sperm can stay in a women's reproductive system is 3-4 .. so mathematically 8 +4 = sept 12 .. ovulation wouldnt have taken place that day therefore no fertilization occurred since the egg wasnt even released & the answer therefore is B

 

[L-Girl]

to answer ur question ... look at the calender ovulation doesnt occur until sept 15 .. the max days a sperm can stay in a women's reproductive system is 3-4 .. so mathematically 8 +4 = sept 12 .. ovulation wouldnt have taken place that day therefore no fertilization occurred since the egg wasnt even released & the answer therefore is B

thankssss a lot