Determination of the Percent Oxygen in Air

The experiment for today is determination of percent oxygen in air. Here is a video  as reference.

[Source: http://www.youtube.com/watch?v=xQNl2EdteDE ]

What’s going on?

Air is composed of Nitrogen - about 78%, Oxygen

about 21%, Argon about 1% and other gasses.

These gasses compose 100% of the air so they exert

100% of the pressure. IN the test tube, at the

beginning, there was the same pressure inside the

test tube as outside. As the steel wool started to

rust*, the oxygen was taken out of the air, therefore

the pressure was reduced. Over time, the pressure

was reduced by the percentage of oxygen

removed…. about 21%. As the pressure drops, the

pressure on the outside of the test tube pushes the

water level up inside the test tube.

Source