I need an experiment that proves that O2 is 21% of air. PLEASE!?

Question

I need this for chem to morrow and he said get it anyway you can. I'll still be looking for it but I will def. need help..... HELP ME PLEASE!!!!!!!!!!!!!!!!!!!!!!!

Answer 1

First, ignore what tspbrady suggested. It can't work. Burning carbohydrates such as wood or paper will only succed in replacing each mole of oxygen with a mole of water vapour or carbon dioxide. The number of moles of gas will remain identical and so wiil the volume.

Igniting a metal such as magnesium will work approximatelybecause the oxidtaion products are solid and not gaseous.

If you can't find magnesium then steel wool will aso burn quite easily. Simply apply a match. However be aware that steel contains a small amount of carbon that will affect your results by producing carbon dioxie. Probably not measurable, but worth knowing about.

You also don't need to worry too much about electric ignition. SImply light you material and then invert the beaker. You are only interested in lost gas volume, you don't care how much material oxidises BEFORE the system is closed.

Answer 2

I'm not sure if this would work, but it might so try it and let me know:

You need a beaker, a match, and a bathtub (or some such large water-holding device).

Light the match, and hold it so that your arm is under water but the match is above water. Put the beaker upside down over the top of the match so that the open part is *slightly* underwater (creating a seal).

Let the match burn all of the oxygen out of the air in the beaker. Since the O2 is gone (oxidation reaction), the O2 must be replaced by water coming from the tub.

Measure how far the water moves up on the side of the beaker, and that should correspond to the oxidation reagents...

(hey, I didn't say it would be easy!!!)

Answer 3

It's a bit harsh, but you can follow the example of the first scientist to postulate that oxygen is roughly one fifth of the atmosphere. Start by first placing a mouse under a bell jar holding regular air and recording the time it takes the little fellow to pass out (be quick in lifting the jar so he doesn't die!) then follow by filling the jar with pure O2 and repeating the observations. The time should be five times as long in the pure O2 environment.
No joke this is how the first guy did it.

Now after reading that please understand that I don't think you should really do that to the little guy, so instead go with the volume measurement idea.

take a flat piece of cork, a water receptacle, some wooden matches and a volumetric measuring device (a 100 mL graduated cylinder is fine).

Fill container with water and pierce the cork with a match so that it is vertical in the water. Make sure that the mouth of your measuring device fits freely over the cork so that it makes a good seal with the water but also so the cork can float up into the device. With the cylinder over the cork and water mark the water level in it. Now lift the device and light the match then gently replace the cylinder back over it making sure it seals with the water. As the oxygen is burned up its volume is replaced with the water and the water will rise into the cylinder. So in a 100mL cylinder you should add 21 mL of water after the match extinguishes itself. Make sure you use a large enough match and a tall, slender cylinder for best results. This is not a precise method (you'll come up in the ball park of 20-25% composition if you do it three or four times) and I'll leave the justification of your findings up to you, but it DOES work (just tested it), is fun to watch and no little fellows get hurt in it.
Well, I hope that helps.

Answer 4

How can I refuse when you are asking so nicely?

Glass measuring cylinder turned upside down in water.
Burn a little Mg inside cylinder, using electric spark.
The air volume will shrink by 21%

Answer 5

Get an O2 sensor or calculate the calories produced by burning some fuel and calculation the o2 ratio necessary to make it combust.

Answer 6

what kind of material do you have?