Chemistry Paper 1 Doubts Here... !

[haochen]

doubt no.1:
in the salt water because iron rust in the presence of water and oxygen
but there are two factor which increases rusting which is
1) salt
2) acid
engine oil contain oil so it doesnt contain water and prevent oxygen from entering

doubt two:
it is D.(one and three)
because it need to have low density so it wont be so heavy that the plane cant lift off
and it hv high strength so that it wont broke or bitter in extreme condition
while good conductivity shudnt be there coz when there is a lighting storm the lighting
will direct it direction so the plane will be in danger the BOOOOOOMM


hope i clear ur doubt

dont hesitate to ask more coz i can help u

 

[AStarHunter]

thnx guyz so much :lol:

 

[haochen]

ur welcm

 

[phro5031]

Q2 WOULD BE A ,( 1ONLY ) , IN ORDER TO MAKE AN AIRCRAFT , IT NEEDS LOW DENSITY WE NO CORROSION , BUT NOT HIGH STRENGTH!! , AS I READ IN ANOTHER DISCUSSION , THAT'S HOW IT WAS ANSWERED !!!! ardon: :Search:

 

[moonlight22]

nooooo it needs strength i`m sure 100%

 

[moonlight22]

test for water:
cobalt chloride (s) + water (l) ---> cobalt chloride.water (s)
why the product is also a solid ?
isn`t it hydrated ?
this is what was written in my textbook

 

[phro5031]

nooooo it needs strength i`m sure 100%

WHY ARE YOU SO SURE?? HOW DID YOU KNOW??? ardon:

 

[moonlight22]

coz i read the M.S b4 and it mentioned this
AND an aircraft SHOULD be strong and light << logic

 

[Outofideaz]

ok my question is: wats the reaction to make sodium carbonate NaCO3?

 

[moonlight22]

test for water:
cobalt chloride (s) + water (l) ---> cobalt chloride.water (s)
why the product is also a solid ?
isn`t it hydrated ?
this is what was written in my textbook

wow none of u knows why

 

[AStarHunter]

well, i am not sure but i think when you add water, it forms crystals (?!)
isn`t it the same idea as anhydrous copper sulphate white powder, when u add water, it becomes hydrated copper sulphate crystals.
I am not really sure but at least i tried answering

 

[AStarHunter]

coz i read the M.S b4 and it mentioned this
AND an aircraft SHOULD be strong and light << logic

What mark scheme was that ?

 

[moonlight22]

well, i am not sure but i think when you add water, it forms crystals (?!)
isn`t it the same idea as anhydrous copper sulphate white powder, when u add water, it becomes hydrated copper sulphate crystals.
I am not really sure but at least i tried answering

I think u r right , as a precipitate is formed ,. yeeeeeees now i got it , thanks 8)

 

[JmCullen]

coz i read the M.S b4 and it mentioned this
AND an aircraft SHOULD be strong and light << logic

What mark scheme was that ?

hmm.. what i think it should be strong too!
as you know, alloy is strong. if it doesnt need to be strong, they could have just use aluminum..
why should they made it as an alloy?
look this website..
http://www.cast-parts.com/castings/why- ... t-parts-3/

 

[haochen]

ok my question is: wats the reaction to make sodium carbonate NaCO3?

use any metal in the reactant eg. :
sodium chloride + magnesium carbonate -------> sodium carbonate + magnesium chloride (displacement reaction)


hope u got it

 

[haochen]

test for water:
cobalt chloride (s) + water (l) ---> cobalt chloride.water (s)
why the product is also a solid ?
isn`t it hydrated ?
this is what was written in my textbook

hydrated doesnt mean it shuld be liquid, it mean that the solid contain water molecule inside it.
and if a solid absorb water,it wont turn into liquid while it will just suck up the water and make it
part of it.

srry for the later answer coz i was buzy
hope i helped

 

[JmCullen]

explain why sometime acid is acting as a base???
i found this question in some past papers (paper 3)
but i forgot why..

 

[haochen]

can u post the link to the paper coz i dont understand

and i just came across queston like :
why is water acting as a base

 

[JmCullen]

can u post the link to the paper coz i dont understand

and i just came across queston like :
why is water acting as a base

i forget which paper.. it's in one of the paper 3..
cuz i'm reading the examiner tips.. and i realised i ever did that question..

here is the notes from the examiner tips..

The phrase ‘explain why this acid is acting as a base’ demands a chemical reason (usually based on particle theory). The examiner is looking for an answer involving proton transfer. Vague answers (such as ‘it is neutralising the base’) are not accepted as they do not give an explanation (3.2(b)(iv))

 

[JmCullen]

can u post the link to the paper coz i dont understand

and i just came across queston like :
why is water acting as a base

oh! why is water acting as a base?