Chemistry Help HERE ONLY !!

[zara]

hahaha lol thukon
anywayz i have a question for everybody
how would u find the percentage of oxygen in a gas jar that contains 150 cm3 of air?

i hv a realli gud bk>>>GCSE edition>>Chemistry made clear...
in it there is an experiment to show the % of oxygen present in 100cm³

The apparatus:
Is a hard tube glass, connected to two gas syringes, A and B. The tube is packed with small pieces of pink copper wire. One syringe contains 100cm3  of air and the other is empty.

The experiment:
1.The tube is heated by a bunsen.When the plunger of syringe A is pushed in, the air gets forced thru the heated tube, into B. As the air passes over the hot copper wire, the oxygen in it reacts with the wire, which starts to turn black. Next the plunger of B is pushed in, so the air is forced back to A. This is repeated several times.

2. After about 3 mins, heating is stopped. The apparatus is allowed to cool down. Then all the gas is pushed into one of the syringes and its volume measured.(The volume is now less than the 100cm3).

3.Steps 1 and 2 are repeated until the volume of gas no longer decreases. This is a sign that all the oxygen in the syringe has been used up. The final volume is noted.

The results:
Vol of gas at start:100cm3
Vol of gas at end:79cm3
Vol of gas used up:21cm3
So 100cm3 of air contains 21cm3 of oxygen.
therefore,, % of oxygen=(21/100)*100=21%

[unknown 101]

lol i removed it , cuz it was also pissing me off


its a good way to find outt ow much oxygen was there, but thats going to take u about 3 days, cuz rusting is a slow process, but its right and u forgot that i asked for PERCENTAGE not volume

nice try zara , but i asked for a 150 cm3 not a 100cm3, but the way u choose to do it is the correct way!!

[zara]

yea i kno u askd for 150cm3 but then its the same way...actually this is exactly wats written in the txt bk....
so instead of 100cm3 u take 150 cm3 n do the experiment..

[unknown 101]

if u change the 100 cm3 to 150cm3 and say the volume of oxygen present is 31.5
and do 31.5/150 x 100 = 21%

[nid404]

so any which ways it's 20% of the total volume of air. Any method will do

[12345abc]

here's some problems i had:
1.how do we write overall equations,e.g for habers process?
2. rust prevention-the mechanisms
3.why is a crucible in which magnesium oxide is being made covered with a lid?
4.colour of flame when there is incomplete combustion?
5.what reacts at room temp. with ethanol and ethanoic acid?
 A. CaCO3     B.CuO     C.CH3OH     D.Na
6.what are synthetic macromolecules?


please help!!!

[unknown 101]

so any which ways it's 20% of the total volume of air. Any method will do

could be 20% or 21%

[nid404]

so any which ways it's 20% of the total volume of air. Any method will do

could be 20% or 21%

yes sir

[twilight]

4.colour of flame when there is incomplete combustion?

its red or orange .. a clean flame is blue

[unknown 101]

here's some problems i had:
1.how do we write overall equations,e.g for habers process?
2. rust prevention-the mechanisms
3.why is a crucible in which magnesium oxide is being made covered with a lid?
4.colour of flame when there is incomplete combustion?
5.what reacts at room temp. with ethanol and ethanoic acid?
 A. CaCO3     B.CuO     C.CH3OH     D.Na
6.what are synthetic macromolecules?


please help!!!

1) i dont understand wat u mean!!
2)to prevent rust u could, paint the object, greasing or oiling, plastic coating, chromium plating, galvanizing with zinc, using stainless steel (which is corrosion resistant)
3)depends on the process if ur heating molten or aqueous substances then to prevent the splashing out of materials
4)blue = complete.. orange= incomplete
5) C), i think, cuz its the only organic substance  ( ASK SOMEONE ELSE CUZ IM NOT SURE!!)
6)these are man-made polyamide and polyester eg. nylon and terylene

[SGVaibhav]

vaibhav have a look at the pdf

I have drawn the structure of the nylon

is it ok if i get the H above the N
 

like
                                 H
                                 !
......................  . . . .  N

[unknown 101]

vaibhav have a look at the pdf

I have drawn the structure of the nylon

is it ok if i get the H above the N
 

like
                                 H
                                 !
......................  . . . .  N

yeah no problem in doin that

[SGVaibhav]

ok thank you

[thukon]

here's some problems i had:
1.how do we write overall equations,e.g for habers process?
2. rust prevention-the mechanisms
3.why is a crucible in which magnesium oxide is being made covered with a lid?
4.colour of flame when there is incomplete combustion?
5.what reacts at room temp. with ethanol and ethanoic acid?
 A. CaCO3     B.CuO     C.CH3OH     D.Na
6.what are synthetic macromolecules?


please help!!!

1) i dont understand wat u mean!!
2)to prevent rust u could, paint the object, greasing or oiling, plastic coating, chromium plating, galvanizing with zinc, using stainless steel (which is corrosion resistant)
3)depends on the process if ur heating molten or aqueous substances then to prevent the splashing out of materials
4)orange = complete.. blue= incomplete
5) C), i think, cuz its the only organic substance  ( ASK SOMEONE ELSE CUZ IM NOT SURE!!)
6)these are man-made polyamide and polyester eg. nylon and terylene

Lil wayne, uve got the flames mixed up. Blue is complete. Red or orange is incomplete.
The answer is not C for the other thing. I m sure, because C is methanol. Im pretty sure methanol and ethanol dont react at room temp, but i dont know the answer.

[zara]

wait a min...
twilight said that red/orange in case of incomplete combustion....
lilwayne says:orange for complete combustion..

so now whch one is correct??