Oxygen in the air

The percentage of oxygen in the air can be measured by passing a known volume of air over hot copper, and measuring the decrease in volume as the oxygen reacts with it. Here are the equations for this reaction:

copper + oxygen    →    copper oxide

2Cu + O₂    →    2CuO

Gas syringes are used to measure the volume of gas in the experiment. The starting volume of air is often 100cm³ to make the analysis of the results easy, but it could be any convenient volume. In the simulation, there is 100cm³ of air at the start.

Note that there is some air in the tube with the copper turnings. The oxygen in this air will also react with the hot copper, causing a small error in the final volume recorded. It is also important to let the apparatus cool down at the end of the experiment, otherwise the final reading will be too high.