Physics, Chemistry and Biology: Post your doubts here!

[MERIHAN]

i) Describe the chemistry of making butanol from petroleum by the following route.
petroleum → butene → butanol
plz answer !!! thanks in advance
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s11_qp_31.pdf ( q no 6 a (1) )

 

[Nimaay]

cracking and than adding steam to the butene

 

[EpicLol]

How to do 3 a) i) and ii) ?
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s11_qp_32.pdf
I don't think I'm going to do well in this exam

i) Accuracy, fair test....
ii)240 but im not sure why or how...

 

[T19]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s05_qp_3.pdf
QUESTION 1 C THE PRODUCT OF THE EQUATION I GET IS 2ICL
BUT IN THE MARK SCHEME IT IS 2ICL3 WHY ??
THANX IN ADVANCE

 

[Ritter]

Could you please explain to me this question november 2000

I've read the ms but I didn't understand ms says:

But I think instead of 20ml we should put only 5 ml if its H2Y

Thanks in advance

 

[Iridescent]

Could you please explain to me this question november 2000

I've read the ms but I didn't understand ms says:

But I think instead of 20ml we should put only 5 ml if its H2Y

Thanks in advance

It is 5ml. Where did u get this answer from?
we take the ratio of the reactants in the reaction.
HY+NaOH-->NaY + H2O
Ratio: 1:1

H2Y+2NaOH-->Na2Y+2H2O
Ratio:1:2

Therefore, quantity of both the reactants (acid and sodium hydroxide) is same for the reaction to get over, HY is correct. And if half the acid (5ml) is used, H2Y is correct!

 

[Ritter]

It is 5ml. Where did u get this answer from?

from mark scheme (old one)
from here: http://www.xtremepapers.com/communi...for-chemistry-3-physics-6-with-answers.16759/
link : http://www.xtremepapers.com/community/attachments/chemistry1993-2000answers-pdf.11136/

Anyways Thanks for the explanation

 

[thats_me]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s05_qp_3.pdf
QUESTION 1 C THE PRODUCT OF THE EQUATION I GET IS 2ICL
BUT IN THE MARK SCHEME IT IS 2ICL3 WHY ??
THANX IN ADVANCE

Read the question again , We need to find the mole ratio and then balance
so 0.015 :0.045 :0.03
i.e 1 : 3 : 2
so balance the equation: I2 +3Cl2 --->2ICl3 (Iodine trichloride)
I2 + Cl2 ---> 2ICl
ICl + Cl2 ---> ICl3 actually , this is how the equation is but they comined both of them.

 

[Iridescent]

from mark scheme (old one)
from here: http://www.xtremepapers.com/communi...for-chemistry-3-physics-6-with-answers.16759/
link : http://www.xtremepapers.com/community/attachments/chemistry1993-2000answers-pdf.11136/

but that can't be correct, no logic. this answer (the 5ml one) has been given by my teacher

 

[Tuba noor]

what will be the change in volume of 30m^3 gas if itr temp is reduced 3 times ??

 

[NIM]

What is the function of Human blood system???

 

[Rania MD]

Hello, I have a Biology Question that I cannot seem to understand.
This is the link:
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_s06_qp_1.pdf
It's Q. 35
The problem is I answered A and I have got no idea why it's wrong.(denitrifying bacteria do return nitrogen back to the atmosphere. And they are decomposers?!)
Thanks!

 

[thats_me]

What is the function of Human blood system???

Maintain temperature (Homeostasis)
transport substances such as nutrients, oxygen..
protect against dieseases (lymphocytes & Phagocytes)

 

[thats_me]

Hello, I have a Biology Question that I cannot seem to understand.
This is the link:
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_s06_qp_1.pdf
It's Q. 35
The problem is I answered A and I have got no idea why it's wrong.(denitrifying bacteria do return nitrogen back to the atmosphere. And they are decomposers?!)
Thanks!

This is because decomposers feed on the dead matter and respire producing carbondioxide and water, i guess this question is generally for decomposers not for a specific cycle..

 

[Rania MD]

This is because decomposers feed on the dead matter and respire producing carbondioxide and water, i guess this question is generally for decomposers not for a specific cycle..

yes but they also decompose dead matter and release nitrogen from protein rich wastes, so why doesn't that count as well ? :/

 

[thats_me]

yes but they also decompose dead matter and release nitrogen from protein rich wastes, so why doesn't that count as well ? :/

I guess bcz all the decomposers respire , but all of them donot release nitrogen n they din ask denitrifying bacteria in particular

 

[Rania MD]

oh alright, I get it now. Thank you very much

 

[thats_me]

oh alright, I get it now. Thank you very much

anytime

 

[Mohsin41]

guys how was chemistry paper? i think only 8-9 marks were somehow difficult but rest was awsome

 

[thats_me]

guys how was chemistry paper? i think only 8-9 marks were somehow difficult but rest was awsome

Yea it was good but i lost marks for stupid mistakes :|