Physics, Chemistry and Biology: Post your doubts here!

[areebaization]

I have the same question.....it came in like one of the past papers I did like ages ago......

i know i saw some videos on youtube and am more confused :/

 

[thats_me]

I have a doubt guys! Since almost all metals are cations and reduction happens at cathode can we say that metals get reduced? OR the substance that gets disposed off (in the form of gas or solid precipitate at the bottom of the beaker) at the electrodes is generally reduced? :S

i think it's the metal that gets reduced..

 

[areebaization]

i think it's the metal that gets reduced..

thanx a bunch

 

[sma786]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w09_qp_31.pdf
Help please,question 6 (c) , second, how do we know its 0.03 ?

 

[thats_me]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w09_qp_31.pdf
Help please,question 6 (c) , second, how do we know its 0.03 ?

2Fe2SO4---->Fe2O3+SO2+SO3
so the ratio is 2:1:1:1
no. of moles of Fe2SO4 = 9.12/152=0.06
moles of Fe2O3=
2 : 1 <--ratio
If 2 is 0.06 thn 1 is how much? cross multiply
so 0.06/2=0.03

 

[xxxt]

I agree with the top two but not the last one....it would be C4H8 and C6H12 and H2 .....

its ok any way is right but the space given in the paper was only for two products so i thought that should do it.

 

[sma786]

2Fe2SO4---->Fe2O3+SO2+SO3
so the ratio is 2:1:1:1
no. of moles of Fe2SO4 = 9.12/152=0.06
moles of Fe2O3=
2 : 1 <--ratio
If 2 is 0.06 thn 1 is how much? cross multiply
so 0.06/2=0.03

thanks alot really helped

 

[xxxt]

I agree with the top two but not the last one....it would be C4H8 and C6H12 and H2 .....

i am sorry i meant C6H14 NOT C6H4

 

[EpicLol]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w09_qp_31.pdf
Help please,question 6 (c) , second, how do we know its 0.03 ?

2 moles of FeSO4 is used....
1 moles
calculate the mass of Fe2O3.....
same as the previous as its its 1 mole only....
1 mole
this one Im not sure.....does anyone know how to calculate volume based on like moles?
Thx

 

[thats_me]

2 moles of FeSO4 is used....
1 moles
calculate the mass of Fe2O3.....
same as the previous as its its 1 mole only....
1 mole
this one Im not sure.....does anyone know how to calculate volume based on like moles?
Thx

yea the formula is Volume=no. of moles*24dm3

 

[EpicLol]

yea the formula is Volume=no. of moles/24dm3

thats a really strange formula... do u know why its /24dm3?

 

[thats_me]

thats a really strange formula... do u know why its /24dm3?

umm umm its a formula never tried to knw the theory behind

 

[thats_me]

umm umm its a formula never tried to knw the theory behind

really sorry its v=no of moles*24dm3

 

[kainat husain]

4b(ii) oxidation is loss of electrons and iodide ions will loss the electrons they took in order to become ions
4b(iii)because ozone makes the iodide to loss their electrons
7a(ii)during crakinga long chain alkane is broken to a long chain alkene and a short chain alkane soo...
it will be
C10H22->C4H8+C6H4

thanxx

 

[EpicLol]

umm umm its a formula never tried to knw the theory behind

lol.... fine....

 

[kainat husain]

4b ii) Because oxidation is loss of electrons.....
iii) Because ozone is being reduced, so it is the oxidant...it is oxidizing the pottasium iodide, by taking its electrons.....

7a ii) decane would break down into bute 1 ene and sixane....(dont remember how u say 6 ) and hydrogen...

hexene? and thnx

 

[kainat husain]

plz plz plz help for this one! this is real tough :/
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w10_qp_31.pdf
q- 4 b- (ii) (iii) how do we know what values we have to take?

 

[thats_me]

plz plz plz help for this one! this is real tough :/
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w10_qp_31.pdf
q- 4 b- (ii) (iii) how do we know what values we have to take?

what values :S
bii higher pressure favours to the side with fewer moles causing the equilibrium position to shift right
biii they can be used again by passing over the heated catalyst

 

[EpicLol]

plz plz plz help for this one! this is real tough :/
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w10_qp_31.pdf
q- 4 b- (ii) (iii) how do we know what values we have to take?

because the higer the pressure the more ammonia is formed as they are squashed together more....due to less space the hydrogen and nitrogen have to join up as there is no space for them to move along by themselves...

 

[sma786]

2 moles of FeSO4 is used....
1 moles
calculate the mass of Fe2O3.....
same as the previous as its its 1 mole only....
1 mole
this one Im not sure.....does anyone know how to calculate volume based on like moles?
Thx

thanku very much