Qualification > Sciences
Chemistry Help HERE ONLY !!
zara:
--- Quote from: LilWayne on May 30, 2009, 12:05:50 pm ---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?
--- End quote ---
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
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