Physics, Chemistry and Biology: Post your doubts here!

[Ahmed Khider]

From which mark scheme?

My marking scheme ...3 years ago i bought a bunch of past papers including chemistry and i found out that it has the ans for these old questions

 

[Ahmed Khider]

Hey guys could someone help me with these questions>>W06 PAPER 1 qno 37,40 and 31???

 

[Abu mota]

Hey guys could someone help me with these questions>>W06 PAPER 1 qno 37,40 and 31???

hi, i assumed it is chemistry
so for Q.31 it is B because oxides of nitrogen doesnt come from the fuel, it is caused by the very high temperatures which allow the nitrogen to bond with oxygen, but the carbon monoxide and sulfur dioxide does come from the fuel.
for Q.37 it is A because a hydrocarbon is a compound made from carbons and hydrogens only and S has oxygen in it and so it is not a hydrocarbon but R is only made from hydrogen and carbon so it is a hydrocarbon, and as crude oil is a mixture of hydrocarbons then R also occurs in crude oil
for Q.40 it is A because the monomer in addition polymerization is only two carbon length and u shud memorize that and there is only 2 hydrogens for each carbon and so it can never be B.
if u dont understand ask again plz

 

[Ahmed Khider]

hi, i assumed it is chemistry
so for Q.31 it is B because oxides of nitrogen doesnt come from the fuel, it is caused by the very high temperatures which allow the nitrogen to bond with oxygen, but the carbon monoxide and sulfur dioxide does come from the fuel.
for Q.37 it is A because a hydrocarbon is a compound made from carbons and hydrogens only and S has oxygen in it and so it is not a hydrocarbon but R is only made from hydrogen and carbon so it is a hydrocarbon, and as crude oil is a mixture of hydrocarbons then R also occurs in crude oil
for Q.40 it is A because the monomer in addition polymerization is only two carbon length and u shud memorize that and there is only 2 hydrogens for each carbon and so it can never be B.
if u dont understand ask again plz

Haha its good that u assumed that im talking about Chemistry becoz im tired of writing it every time ..Thx alottt for your appreciated efforts

 

[za Shadow]

pllzzz help
CHEMISTRY!!!!
nov 01 Q 22 A and C are both correct how come??????
nov 02 Q 26 why D not C???????????
J04 Q 19 why A it should be C????????????????
nov 07 Q 20 why B not D??????????????????
nov 09 Q 4 why A not B????????????????????
PLZZZZ HELPPP

 

[Abu mota]

pllzzz help
CHEMISTRY!!!!
nov 01 Q 22 A and C are both correct how come??????
nov 02 Q 26 why D not C???????????
J04 Q 19 why A it should be C????????????????
nov 07 Q 20 why B not D??????????????????
nov 09 Q 4 why A not B????????????????????
PLZZZZ HELPPP

yea Q.22 is quite tricky the answer is A because if u know from the analysis table if u add silver nitrate to chloride ions u get a white precipitate silver chloride
Q.26 it is C actually D is wrong the ms is wrong
for J04 Q.19 it is A because aluminium and zinc give the same result with sodium hydroxide ( a soluble white ppt) so u cant seperate them but Ammonia for aluminium it forms an insoluble white ppt and zinc is a soluble ppt and so u can seperate them
for Nov 07 carbon is oxidised to carbon dioxide which escapes causing a decrease in mass, while copper when oxidised will form copper oxide which is a solid that settles causing an increase in mass
for Nov 09 i dont know which variant u didnt say i assumed it is variant 1, it is A because the Q says which can be correct and if u started with an element in group 0, then the other element will be in the same group and it will be unreactive and so the answer is A

 

[thats_me]

yea Q.22 is quite tricky the answer is A because if u know from the analysis table if u add silver nitrate to chloride ions u get a white precipitate silver chloride
Q.26 it is C actually D is wrong the ms is wrong
for J04 Q.19 it is A because aluminium and zinc give the same result with sodium hydroxide ( a soluble white ppt) so u cant seperate them but Ammonia for aluminium it forms an insoluble white ppt and zinc is a soluble ppt and so u can seperate them
for Nov 07 carbon is oxidised to carbon dioxide which escapes causing a decrease in mass, while copper when oxidised will form copper oxide which is a solid that settles causing an increase in mass
for Nov 09 i dont know which variant u didnt say i assumed it is variant 1, it is A because the Q says which can be correct and if u started with an element in group 0, then the other element will be in the same group and it will be unreactive and so the answer is A

Are u sure about 26? (the second 1)

 

[Skynox]

pllzzz help
CHEMISTRY!!!!
nov 01 Q 22 A and C are both correct how come??????
nov 02 Q 26 why D not C???????????
J04 Q 19 why A it should be C????????????????
nov 07 Q 20 why B not D??????????????????
nov 09 Q 4 why A not B????????????????????
PLZZZZ HELPPP

- well AGCL is white,they consider it not coloured..Whenever asked for a coloured compound,choose the transition metal one.
-Highly reactive metals don't occur as oxides they occur as chlorides..
-It cleraly states differntiate,..If you used NaOH,then you'll get for both white precipitate and both ppt dissolve in excess.While using ammonia solution,NH4OH,one will dissolve in excess the other won;t
-Since carbon reacts with oxygen to form carbon dioxide which is a gas and so will pass out of the tube and mass decreases..Copper forms a solid oxide which is CuO.
-

 

[Abu mota]

Are u sure about 26? (the second 1)

yes i am because copper doesnt react with hydrochloric acid and zinc does react and so both of these are wrong so the answer must be magnesium and iron

 

[Skynox]

yea Q.22 is quite tricky the answer is A because if u know from the analysis table if u add silver nitrate to chloride ions u get a white precipitate silver chloride
Q.26 it is C actually D is wrong the ms is wrong
for J04 Q.19 it is A because aluminium and zinc give the same result with sodium hydroxide ( a soluble white ppt) so u cant seperate them but Ammonia for aluminium it forms an insoluble white ppt and zinc is a soluble ppt and so u can seperate them
for Nov 07 carbon is oxidised to carbon dioxide which escapes causing a decrease in mass, while copper when oxidised will form copper oxide which is a solid that settles causing an increase in mass
for Nov 09 i dont know which variant u didnt say i assumed it is variant 1, it is A because the Q says which can be correct and if u started with an element in group 0, then the other element will be in the same group and it will be unreactive and so the answer is A

Highly reactive metals don't occur as oxides they occur as chlorides..They tarnish when left in air,that's why NA and K are kept under the surface of paraffin..

 

[Abu mota]

Highly reactive metals don't occur as oxides they occur as chlorides..They tarnish when left in air,that's why NA and K are kept under the surface of paraffin..

which question is that? did he ask for this question?

 

[Skynox]

which question is that? did he ask for this question?

Q.26

 

[Abu mota]

- well AGCL is white,they consider it not coloured..Whenever asked for a coloured compound,choose the transition metal one.
-Highly reactive metals don't occur as oxides they occur as chlorides..
-It cleraly states differntiate,..If you used NaOH,then you'll get for both white precipitate and both ppt dissolve in excess.While using ammonia solution,NH4OH,one will dissolve in excess the other won;t
-Since carbon reacts with oxygen to form carbon dioxide which is a gas and so will pass out of the tube and mass decreases..Copper forms a solid oxide which is CuO.
-

actually silver is a transition metal too and also iron is too it is an exception that silver chloride is white and we know it from the analysis table

 

[thats_me]

yes i am because copper doesnt react with hydrochloric acid and zinc does react and so both of these are wrong so the answer must be magnesium and iron

umm no i was askin abt nov2 26 :S

 

[Abu mota]

Q.26

oh srry i thought it is 2001, i didnt see 2002

 

[Skynox]

actually silver is a transition metal too and also iron is too it is an exception that silver chloride is white and we know it from the analysis table

Oh,yea...those other transition metals.

 

[Abu mota]

the answer for 26 is D, srry didnt see 2002, i thought it is 2001

 

[Abu mota]

w04 Q.32 in the mark scheme it says it is D but imnot convinced, isnt the zinc just covering the iron and doesnt make a part of its composition?

 

[AAnsarii]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Biology (0610)/0610_s09_qp_1.pdf
q 16, what's C?

 

[AAnsarii]

http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s11_qp_11.pdf
plz xplain q 25
also q3
thx