Finding the Percentage of Oxygen in Air Using Copper (Atmosphere)

Question 1

What apparatus do you need?

Answer 1

-2 gas syringes
-Silica tube packed with copper fillings
-A bunsen burner

Question 2

Explain how you can find the percentage of oxygen in air using copper:

Answer 2

1) Push the plunger on one syringe (right one) all the way in and the other (left one) moved out to 100cm³. We now know that the apparatus contains 100cm³ air.

2) Heat the silica tube strongly using a roaring bunsen flame.

3) Push the plunger on the left syringe in, this will cause the air to pass over the heated copper. This pushes the plunger out on the right gas syringe.

4) Push both plungers in sequence so the air system keeps passing over the heated copper.

5) As the copper reacts, move the bunsen burner along the tube so that fresh copper is always heated.

Question 3

What is the colour change of the copper and why?

Answer 3

Pink-brown to black as copper (II) oxide forms.

Question 4

Why does the volume of gas in the syringes fall as the experiment progresses?

Answer 4

The oxygen is consumed by the copper.

Question 5

How can we make sure the experiment is reliable?

Answer 5

Keep pushing the plungers in and out until there is no change in volume and we know all of the copper has reacted.