Biology; Chemistry; Physics: Post your doubts here!

[usama321]

hw about tonight?

ok night it is

 

[starship]

so which one would you say?

u pick

 

[usama321]

u pick

lol i thought you were saying in the night............ lemme see

http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_w08_qp_1.pdf

random pick

 

[starship]

lol i thought you were saying in the night............ lemme see

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_w08_qp_1.pdf

random pick

Lets do this now and another later tonight?

 

[usama321]

Lets do this now and another later tonight?

ok m on it

 

[inquisitiveness]

do you guys know this
Haber process-After passing over the catalyst, the mixture contains 15% of ammonia. It is cooled and
the ammonia liquefies and is separated from the unreacted nitrogen and hydrogen.
They are recycled.

(ii) Only ammonia gas liquefies. Suggest an explanation for this.

 

[Hskk]

22 thought it was bromine

31, messed this one up, was easy

What's the reason behind 18?
Also, why can't it be bromine? I chose C too.

 

[starship]

ok m on it

36

 

[fatima0000]

http://papers.xtremepapers.com/CIE/...l O Level/Chemistry (5070)/5070_s10_qp_21.pdf
Q B6 (f)
help please

 

[usama321]

36

37

19, 25 and 39

 

[usama321]

What's the reason behind 18?
Also, why can't it be bromine? I chose C too.

for 18 the reactants must always be aqueous for precipitation

and it would have been bromine if it had said something like red brown or orange,......... dark brown is iodine in water

 

[usama321]

do you guys know this
Haber process-After passing over the catalyst, the mixture contains 15% of ammonia. It is cooled and
the ammonia liquefies and is separated from the unreacted nitrogen and hydrogen.
They are recycled.

(ii) Only ammonia gas liquefies. Suggest an explanation for this.

ammonia would have a boiling point higher than the other two gases, so it liquifies earlier

 

[usama321]

36

which ones did you get wrong?

 

[usama321]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s10_qp_21.pdf
Q B6 (f)
help please

k according to avagadro's number, one mole of any substance contains 6.02 multiply 10^23 particles. So, number of electrons in nitrogen are 7 so 7 multiply 6.02 into 10^23+ number of electrons of oxygen that is 8 multiply 6.02 * 10^23

 

[inquisitiveness]

ammonia would have a boiling point higher than the other two gases, so it liquifies earlier

what i know is that they cool the whole container,including ammonia nitrogen and hydrogen...i dont understand howthe boiling point relate to t=this?(youre right btw)

 

[usama321]

what i know is that they cool the whole container,including ammonia nitrogen and hydrogen...i dont understand howthe boiling point relate to t=this?(youre right btw)

oxygen boiling point is around -185 something............so if ammonia has a boiling point of lets say -170 (i am just supposing this boiling point), it would liquify earlier than oxygen, thus it would be easily seperated as a liquied

 

[AhsanAfzal]

38. Same. I thought it was bromine. Silly mistake. Should've read DARK brown.
And the plastic depleting natural resource..

even after studying bio, i also couldnt remember brown colour of iodine(it is used for starch test)

 

[AhsanAfzal]

i got 39/40

 

[papajohn]

I usually get no more than 30

 

[usama321]

i got 39/40

great which year though, 2008 or 2005?