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 100cm
3The 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%